2026届高三生物一轮复习课件：“油菜素内酯”情境下的植物生命活动调节

Check for updates JIPB Journal of Integrative Invited Expert Review Plant Biology https://doi.org/10.1111/jipb.13849 Check for updates Understanding brassinosteroid-centric phytohormone interactions for crop improvement Wenchao Yin1.2D,Nana Dong12D,Xicheng Li1.2,Yanzhao Yang1.2,Zefu Lu,Wenbin Zhou, Qian Qian1.2,Chengcai Chu3,4+and Hongning Tong 2+ 1.State Key Laboratory of Crop Gene Resources and Breeding/National Key Facility for Crop Gene Resources and Genetic Improvement,Institute of Crop Sciences,Chinese Academy of Agricultural Sciences,Beijing 100081,China 2.Key Laboratory of Grain Crop Genetic Resources Evaluation and Utilization,Ministry of Agriculture and Rural Affairs,Institute of Crop Sciences,Chinese Academy of Agricultural Sciences,Beijing 100081,China 3.Guangdong Laboratory for Lingnan Modern Agriculture,and the State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources,South China Agricultural University,Guangzhou 510642,China 4.Key Laboratory for Enhancing Resource Use Efficiency of Crops in South China,Ministry of Agriculture and Rural Affairs,South China Agricultural University,Guangzhou 510642,China *Correspondences:Chengcai Chu(ccchu@scau.edu.cn);Hongning Tong (tonghongning@caas.cn;Dr.Tong is fully responsible for the distribution of all materials associated with this article) external signals,ultimately shaping the physio- logical status of the plant.In this review,we introduce BR metabolism and signaling and dis- cuss their role in modulating agronomic traits that directly contribute to grain yield in rice(Oryza sativa),the model plant for crops.We also summarize recent advances in the crosstalk between BRs and other phytohormones in regu- lating agronomic traits in crops.Furthermore,we highlight significant research that provides in- Wenchao Yin Hongning Tong sights into developing high-yielding and stress- resistant crop varieties from the perspective of hormone crosstalk.Understanding the genetic ABSTRACT and molecular mechanisms through which BRs and other phytohormones collaboratively control Brassinosteroids (BRs)play a crucial role in reg- agronomic traits offers new approaches for crop ulating multiple biological processes in plants, improvement. particularly those related to crop productivity and stress tolerance.During their functioning,BRs Keywords:agronomic trait,brassinosteroid,crop,crosstalk engage in extensive and intricate interactions with phytohormone other phytohormones,including auxin,cytokinins, gibberellins,abscisic acid,ethylene,jasmonates, Yin,W.,Dong,N.,Li,X.,Yang,Y.,Lu,Z.,Zhou,W.,Qian,Q., Chu,C.,and Tong,H.(2025).Understanding brassinosteroid- salicylic acid,and strigolactones.These inter- centric phytohormone interactions for crop improvement.J.In- actions facilitate the integration of internal and tegr.Plant Biol.67:563-581. INTRODUCTION are crucial in modulating various agronomic traits directly linked to yield and resistance.These traits include,but Wae n r campoune are not limited to,plant height,leaf angle,tillering,grain number,grain size,as well as adaptations to abiotic and extreme weather events,there is an escalating demand biotic stresses.Recent research has shed light on the for crop varieties with higher yields and enhanced stress molecular mechanisms governing BR regulation in agri- resistance.Plant growth and development are extensively cultural traits and identified several BR-associated genes influenced by phytohormones,which integrate internal with significant potential for breeding applications.As a developmental signals with external environmental factors. result,utilizing BRs has become a key strategy for crop Brassinosteroids(BRs),a class of steroid phytohormones, improvement. 2025 Institute of Botany,Chinese Academy of Sciences. BR-centric hormone crosstalk Journal of Integrative Plant Biology It is increasingly clear that BRs do not function in isolation. (DWARF11),OsD2,OsCPD1 (CONSTITUTIVE PHOTO- Instead,they operate in conjunction with other phyto- MORPHOGENESIS AND DWARFISM1),OsCPD2,and OsBRD1 hormones,including auxin,gibberellins (GAs),cytokinins,ab (see Table 1).Beyond biosynthesis,the level of endogenous scisic acid (ABA),ethylene,jasmonates (JAs),salicylic acid bioactive BRs is also regulated through BR inactivation.Al- (SA),and strigolactones(SLs).These phytohormones engage though research on BR catabolism is still relatively limited,re in extensive interactions,forming a complex regulatory net- cent studies have identified several BR catabolic genes in rice work that maintains hormonal homeostasis and orchestrates such as OsBRD3,OsCYP734A2,and OsBLA2 (BENDING plant growth and adaptation.Importantly,the effects of hor- LAMINA2),that contribute to this process(see Table 1). mone crosstalk depend on various cellular contexts and The BR signaling pathway in rice has been extensively conditions.Factors such as hormone concentration,inter- studied,revealing both conserved and unique signaling com- action duration,cell type or tissue,developmental stage, ponents compared to Arabidopsis(Yang et al.,2024)(see Table stress exposure,and the nature and intensity of the stress all 2).The OsBRI1 (BR INSENSITIVE1)-OsSERKs(SOMATIC EM- influence the outcomes of these interactions.Plants'abilities BRYOGENESIS RECEPTOR KINASEs)complex activates to modulate these delicate hormonal balances likely represent downstream signaling cascades through a series of phos- a strategy that enhances their adaptability to an ever-changing phorylation and dephosphorylation events (Yamamuro et al., environment,providing increased developmental flexibility 2000;Li et al.,2009).OsBRl1 phosphorylates and activates (Depuydt and Hardtke,2011). OsBSKs (BR-SIGNALING KINASEs),which interact with Recent studies have shed light on the molecular OsPPKLs(protein phosphatases with Kelch-like domains)and mechanisms of BRs in the model plant Arabidopsis (Ara- OsGSKs(GSK3/SHAGGY-LIKE KINASEs)as scaffold proteins bidopsis thaliana),including their roles in plant develop- to facilitate the signaling process(Yin et al.,2022).OsPPKLs,in ment,stress responses,and their complex interactions tum,regulate the activity of OsGSKs,the central negative with other phytohormones (Nolan et al.,2020;Han et al., regulators in BR signaling,through dephosphorylation 2023;Guo et al.,2024).However,our understanding of This regulation ultimately affects the activity of OsBZRs how these mechanisms operate within the context of crop (BRASSINAZOLE-RESISTANTs),the master transcription agronomic traits,particularly their interplay with other factors in BR signaling,which modulate the expression of phytohormones,remains limited,which hinders their ap- BR-responsive genes (Bai et al.,2007;Tong et al.,2012). plication in breeding practices.In this review,we aim to Beyond the primary BR signaling pathway perceived by summarize recent progress in understanding BRs'molec- OsBRl1,several studies provide evidence for the existence of ular mechanisms in regulating agronomic traits in crops, an altemative pathway regulated by OsD1/OsRGA1 (rice G with a particular focus on their interactions with other protein a subunit 1)(Wang et al.,2006;Oki et al.,2009a, phytohormones,especially in rice(Oryza sativa),the model 2009b).OsD1 functions with OsTUD1 (TAIHU DWARF1,also plant for cereal crops.We first provide an overview of BR known as OsELF1),an U-box E3 ubiquitin ligase,to modulate metabolism and signaling and their impacts on yield- the BR signaling pathway(Hu et al.,2013).OsTUD1 promotes related traits in rice.Next,we explore the intricate network the ubiquitination and degradation of OsGSK2 in response of hormone crosstalk involving BRs and other phyto- to BRs,a process that is potentially mediated by OsD1 hormones within biosynthetic and signaling pathways that (Liu et al.,2023). influence agronomic traits.Finally,we discuss promising In the BR signaling pathway,each component represents strategies for fine-tuning hormonal homeostasis to en- a family of proteins with homologous members that exhibit hance crop growth and adaptability functional redundancy,differentiation,or dominance.For example,the OsGSK family contains nine members in rice, among which OsGSK1-OsGSK4 function redundantly to BRASSINOSTEROID METABOLISM negatively regulate BR signaling(Liu et al.,2021a).In addi- AND SIGNALING IN RICE tion to mediating BR response,OsGSK5 (also known as OsSK41/TGW3/GL3.3)is also involved in auxin signaling Brassinosteroid biosynthesis involves a complex and intricate (Hu et al.,2018;Ma et al.,2023).Similarly,the four members metabolic network.Cycloartenol,a common precursor in sterol of the OsBZR family (OsBZR1-OsBZR4)play redundant biosynthesis,undergoes a series of reactions-methylation, roles in the regulation of BR signaling,with OsBZR2 sug- reduction,and desaturation-to be converted into campesterol gested to be the dominant member (Liu et al.,2021a). (CR)via the sterol biosynthesis pathway.Campesterol is then OsGSK2 has been demonstrated as a central hub in BR transformed into castasterone(CS)through the action of var- signaling by suppressing the BR response through the ious metabolic enzymes via the BR biosynthetic pathways(Wei phosphorylation of various downstream components(Tong and Li,2020).CS could be the most biologically active form and Chu,2018).Beyond OsBZR1,a range of transcription of BRs in rice(Kim et al.,2008).Key genes identified in rice that factors have been identified as substrates of OsGSK2 participate in these two biosynthetic pathways include These include OsDLT (DWARF AND LOW-TILLERING) OsCYP51G3,OsCYP51H3,OsBRD2(BR-DEFICIENT DWARF2, (Tong et al.,2009),OsSMOS1 (SMALL ORGAN SIZE1)/ also known as OsDIM/OsDWF1),OsDWF4(DWARF4),OsD11 OsRLA1 (REDUCED LEAF ANGLE1)(Hirano et al.,2017; 564 March 2025 Volume 67 Issue 3 563-581 www.jipb.net Journal of Integrative Plant Biology BR-centric hormone crosstalk Table 1.Functionally characterized brassinosteroid(BR)metabolism genes in rice Process Gene name LOC Function Agronomic traits References Sterol OSCYP51G3 LOC_0s05g12040 14g-demethylase Plant height;leaf angle; Xia et al.(2015) biosynthesis fertility;salt stress response OSCYP51H3 LOC_Os07g28110 14a-demethylase Plant height;leaf angle; Jiao et al.(2022) grain filling;grain size; flowering time BR OsBRD2/DIM/ LOC Os10g25780 △24 reductase Plant height;leaf angle; Hong et al.(2005);Liu biosynthesis DWF1/LTBSG1/ grain number;fertility; et al.(2016b);Qin Ihdd10 grain size;root etal.(2018) development; heading date OsDWF4/ LOC Os03g12660 C22 hydroxylase Plant height;leaf angle Sakamoto et al.(2006) CYP90B2 OsD11/ LOC Os04g39430 C22 hydroxylase; Plant height;leaf angle; Tanabe et al.(2005);Sakamoto CYP724B1/CL4/ C-3 reduction grain number;fertility; et al.(2006);Guo SG4/CBP1/ grain size;germination et al.,(2014);Shi et al.(2015); GNS4/ Zhu et al.(2015a);Wu et al. NBG4/PMM1 (2016);Zhou et al.(2017);Li et al.(2018b);Tong eta.(2018) OsD2/CYP90D2/ LOC Os01g10040 C23 hydroxylase; Plant height;leaf angle; Hong et al.(2003);Sakamoto SMG11 C3 oxidase grain size;tiller angle et al.(2012);Li et al (2013);Dong et al. (2016);Fang et al.(2016) OsCPD1/CYP90A3 LOC Os11g04710 C3 oxidase OsCPD1 and OsCPD2 Sakamoto and Matsuoka, OSCPD2/CYP90A4 LOC_Os12g04480 C3 oxidase redundantly regulate 2006;Zhan et al.(2022) plant height;leaf angle; grain size;panicle length and architecture OsBRD1/ LOC Os03g40540 C6 oxidase Plant height;leaf and root Hong et al.(2002);Mori OsDWARFI development;tiller etal.(2002) OsBR6ox number;fertility BR catabolism OsBRD3/CL/ LOC_Os06g39880 Hydroxylase and Plant height;leaf and floral Sakamoto et al.(2011);Qian CYP734A4 oxidase organ development; et al.(2017);Zhang grain number etal.(2024) CYP734A2 LOC Os02g11020 Hydroxylase and Plant height;leaf and floral Sakamoto et al.(2011) oxidase organ development OsBLA2/ LOC Os01g29150 Hydroxylase and Plant height;leaf and floral Park et al.(2006);Sakamoto CYP734A6 oxidase organ development;leaf etal.(2011) angle Qiao et al.,2017),OsOFPs (OVATE FAMILY PROTEINs) adaptability to dynamic developmental and environmental (Yang et al.,2016;Xiao et al.,2017,2020),OsWRKY53(Tian conditions. et al.,2021),OSLIC (LEAF AND TILLER ANGLE INCREASED CONTROLLER)(Zhang et al.,2012),OsGRF4 (GROWTH- REGULATING FACTOR 4)(Che et al.,2015),OsDLA(DE- AN OVERVIEW OF BR REGULATION CREASED LEAF ANGLES)(Meng et al.,2023),and OF YIELD-RELATED TRAITS IN RICE OsNAC016 (Wu et al.,2022).Among these,OsSMOS1 is reported to interact with both OsDLT and OsBZR1 (Hirano Grain yield per unit area of cereal crops is determined by et al.,2017;Qiao et al.,2017),while several OsOFP mem- three key component traits:panicle number per unit area, bers have been found in association with OsDLT(Xiao et al., grain number per panicle,and grain weight(Xing and Zhang, 2017,2020).Additionally,OsWRKY53 has been shown to 2010).Among these,the number of panicles per unit area is interact with OsBZR1 (Tian et al.,2021).These interactions significantly influenced by planting density.High-density suggest that these transcription factors,along with the planting can increase the number of panicles,but this is regulatory factors they engage with,likely assemble into a contingent upon conditions that favor such dense planting. sophisticated transcriptional complex.This complex fine- Therefore,plant architecture-encompassing plant height, tunes BR-responsive processes,enhancing plasticity and leaf angle,and tiller number-can serve as an indicator of www.jipb.net March 2025 Volume 67 Issue 3 563-581 565 BR-centric hormone crosstalk Journal of Integrative Plant Biology Table 2.Functionally characterized genes in the primary brassinosteroid(BR)signaling pathway in rice Gene name LOC Function Agronomic traits References OsBRI1/SMG12 LOC_Os01g52050 BR receptor Plant height;leaf angle; Yamamuro et al. grain size;shoot and floral (2000);Nakamura organ development etal.(2006) OSSERK1/ LOC_Os08g07760 BR co-receptor Plant height;leaf angle; Li et al.(2009);Liao et al. OsBAK1/ grain size;root (2016;Lin et al..(2017 OsTBP1 development;immunity OsSERK2 _OC_Os04g38480 BR co-receptor;feedback Plant height;leaf angle; Chen et al.(2014);Dong attenuating the BR response grain size;salt stress et al.(2020);Du response;immunity etal.(2023) OsBSK1-1 LOC Os03g04050 As a scaffold protein bridging Plant height;tiller number; Tian et al.(2023) OsBRI1 and OsGSK2 grain size OsBSK1-2 LOC Os10g39670 Immunity Immune responses Wang et al.(2017) OsBSK2/ LOC Os10g42110 A scaffold protein that interacts Plant height;leaf angle; Yin et al.(2022);Yuan et al. GLW10 with OsBRI1,OsPPKL2 and grain size;tiller number (2022b) OSGSK2 OSBSK3 L0C_Os04g58750 Binds to BSU1 to regulate BR Plant height;leaf angle; Zhang et al.(2016) signaling grain size OsPPKL 1/GL3 LOC Os03g44500 Dephosphorylates and Plant height;leaf angle; Gao et al.(2019);Liu et al. stabilizes OsGSK3; grain size;tiller number (2022b) suppresses OsAHP2-to-RR21 phosphorelay in cytokinin signaling OSPPKL2 LOC Os05g05240 A positive regulator in BR Plant height;leaf angle; Liu et al.(2021a) signaling grain size;tiller number OSPPKL3 LOC Os12g42310 Might function redundantly with Grain size Liu et al.(2021a) OsPPKL1 and OsPPKL2. OSGSK1 LOC Os01g10840 Might be a negative regulator of Grain size;abiotic stress Koh et al.(2007) BR signaling response OsGSK2 L○C_Os05g11730 Phosphorylates many Plant height;leaf angle; Tong et al.(2012);Tong and substrates and suppresses grain size Chu2018) BR signaling OSGSK3 LOC Os02g14130 Phosphorylates and inactivates Leaf angle;grain size;tiller Gao et al.(2019) OsBZR1 number OsGSK5/ LOC Os03g62500 A negative regulator in BR Grain size;amylose content; Thitisaksakul et al.(2017);Hu OSSK41/ response abiotic stress response et al.(2023);Ma TGW3/GL3.3 etal.(2023 OsBZR1 LOC_Os07g39220 Regulates BR-responsive gene Plant height;leaf angle; Bai et al.(2007);Zhu et al. expression grain size;tiller number; (2015a);Ke et al. fertility;germination; (2020);Xiong et al. immunity (2022:An et al..(2023) OsBZR2 LOC_Os01g10610 Might play a dominant role in Plant height;tiller number; Liu et al.(2021a) the OsBZRs family grain size panicle number per unit area.BR-deficient and BR-insensitive Brassinosteroid regulation of panicle number per unit mutants often exhibit pleiotropic phenotypes such as area/plant architecture dwarfism,erect leaves,reduced tillering,and smaller grains, The semi-dwarf height trait is highly valuable for its role in en- underscoring the essential role of BRs in directly regulating hancing lodging resistance in crops.Recent research suggests these yield-related traits.Since the function and molecular that genes associated with BRs hold significant promise mechanisms of BRs in regulating agronomic traits have been for developing high-yielding dwarf varieties in crop breeding comprehensively reviewed(Tong and Chu,2012,2018;Chen (Niu et al.,2022;Song et al.,2023).Brassinosteroids work in et al.,2024;Yang et al.,2024;Zhao et al.,2024),in this concert with GAs and other phytohormones to regulate cell section,we provide a brief overview of how BRs impact yield- elongation and plant height.Furthermore,BRs play a role in related traits in rice(Figure 1).In the subsequent section,we the differential elongation of internodes in rice,a process will emphasize on a more detailed analysis of how these in- vital for the development and organization of other organs,in- teractions between BRs and other phytohormones regulate cluding leaves and panicles.Specifically,the protein OsDLT yield-related traits and stress adaptation in crops. interacts with OsOSH15 (ORYZA SATIVA HOMEOBOX 15),a 566 March 2025 Volume 67 Issue 3 563-581 www.jipb.net Journal of Integrative Plant Biology BR-centric hormone crosstalk Panicle number per unit area Grain number per panicle Plant architecture -BR +BR Tissue-specific BR inhibition Prolonged SBM Grain weight -BR +BR Expansion Grain filling 31/0 Proliferation Figure 1.Regulation of yield-related traits by brassinosteroids(BRs)in rice Grain yield per unit area is determined by three component traits:panicle number per unit area which largely depends on plant architecture,grain number per panicle,and grain weight.Plant architecture in rice mainly related to agronomic traits including plant height,leaf angle,and tiller number.BRs promote cell elongation in the intemode to increase plant height.BRs increase leaf angle by suppressing abaxial sclerenchyma cell proliferation,promoting adaxial cell expansion,and inhibiting lignin deposition in sclerenchyma cells.BRs promote tiller bud outgrowth to positively regulate tiller number.Tissue-specific BR inhibition enhances panicle branching and grain number per panicle.BRs enhance grain weight through promoting cell expansion,cell proliferation,and grain filling.ad,adaxial;ab,abaxial;SBM,secondary branch meristem. homeodomain-containing protein,to enhance the trans- homolog of AtBIN2 (BRASSINOSTERIOD-INSENSITIVE2),a activation effect of OsOSH15 on OsBR/1 in a dose-dependent central negative regulator in BR signaling in Arabidopsis,which manner.OsOSH15 exhibits stronger expression in lower inter- further inhibits the phosphorylation and activity of OsCYC U4;1 odes,whereas OsDLT displays an opposite expression patter. (Sun et al.,2015).Further,lignin,one of the main components of The differential levels of the OsDLT-OsOSH15 complex on in the cell wall,offers the necessary mechanical strength essential temodes ultimately lead to distinct effects on BR responses for maintaining leaf erectness.A recent study has shed light on thereby regulating intemode organization(Niu et al.,2022). the role of BRs in shaping leaf angle by regulating lignin dep- An optimal leaf angle enhances light capture for photosyn- osition.OsBZR1 directly targets OsFLP (FOUR LIPS),which thesis,improves ventilation,and increases stress resistance encodes an atypical R2R3-MYB transcription factor that pref- under high-density planting conditions,thereby boosting grain erentially expresses in the lamina joint region.OsFLP promotes yield per unit area(Cao et al.,2022).Leaf angle is particularly lignin deposition in sclerenchyma cells through stimulating the sensitive to BR levels;as BR concentration rises,the leaf angle transcription of the phenylalanine ammonia-lyase family genes correspondingly enlarges.Research has shown that BRs stim- (Liu et al.,2024).Collectively,these findings indicate that BRs ulate cell elongation in the lamina joint,where the leaf blade decrease the proliferation of abaxial sclerenchyma cells while connects to the leaf sheath (Zhang et al.,2009;Jang et al., promoting the enlargement of adaxial cells.Furthermore,BRs 2017).Anatomical studies reveal that BRs promote the ex- are found to inhibit lignin deposition in the lamina joint. pansion of adaxial cells and the formation of adaxial cell bumps This orchestrated balance of cellular regulation results in an at the lamina joints (Cao and Chen,1995;Duan et al.,2006) increased leaf angle. Additionally,BRs inhibit the proliferation of abaxial scler- Tiller number per plant is a key determinant of panicle enchyma cells through OsCYC U4;1,a U-type cyclin that reg- number,which in turn is crucial for grain yield.Typically, ulates cell division.BR signaling suppresses OsCYC U4;1 mutants deficient in BR biosynthesis/metabolism or defective expression likely via a rice homolog of AtBES1 (BRI1-EMS- in BR signaling exhibit reduced tiller numbers,whereas plants SUPPRESSOR1),a key transcription factor in BR signaling in with enhanced BR signaling show increased tiller numbers. Arabidopsis.Concurrently,BR signaling likely inactivates a This suggests that BRs positively regulate tiller number in rice www.jipb.net March 2025 Volume 67 Issue 3 563-581 567 BR-centric hormone crosstalk Journal of Integrative Plant Biology (Fang et al.,2020).Further analysis indicates that BRs pro- expansion,proliferation,and grain filling during grain devel- mote tiller bud outgrowth by interacting with SLs and GAs opment,it is evident that BRs significantly influence grain (Fang et al.,2020;Wu et al,2020).Additionally,in ratoon weight control.BR-deficient and BR-insensitive mutants, rice,BRs have also been implicated in the germination of such as d2,d11,and bsk2,typically produce shorter grains axillary buds,adding another dimension to the regulatory due to reduced cell size,suggesting that BRs enhance grain network governing rice tillering (Xu et al.,2020). length by promoting cell expansion in the spikelet hulls(Hong et al.,2003;Tanabe et al.,2005;Yin et al.,2022).Additionally, Brassinosteroid regulation of grain number per panicle some BR signaling components,such as OsPPKL1 and Increasing the number of grains per panicle is considered an OsGSK2,are involved in cell proliferation (Qi et al.,2012;Liu effective strategy for enhancing grain yield in breeding pro- et al.,2017).Recent research has also highlighted that BRs' grams (Lu et al.,2022).Several BR-deficient mutants exhibit role in cell division involves crosstalk with cytokinins (Liu variations in grain number per panicle,with either a decrease or et al.,2022b).Furthermore,BRs facilitate sugar partitioning an increase observed (Hong et al.,2005;Fang et al.,2016; by activating the expression of OsCSA(CARBON STARVED Lin et al.,2017).Additionally,two allelic mutants,pmm 1(panicle ANTHER),a MYB transcription factor gene,which enhances morphology mutant 1)and nbg4(notched belly grain4),resulting the flow of assimilates from source to sink tissues and from OsD11 truncation and deletion,respectively,display thereby regulates grain filling and weight(Wu et al.,2008;Zhu clustered panicle (Tong et al.,2018;Li et al.,2018b).These et al.,2015a) findings imply that BRs may regulate grain number by influ- encing the development of spikelet meristems,although the precise molecular mechanisms remain unclear. BRASSINOSTEROID Our recent research elucidates the molecular mechanism by which BRs regulate grain clustering and number.In the INTERACTIONS WITH OTHER study of clustered-spikelet (CL)rice,which features multiple PHYTOHORMONES TO INFLUENCE complete spikelets or grains clustered on the panicles, IMPORTANT AGRONOMIC TRAITS we have cloned the causal gene OsBRD3.Due to the structure variations in OsCL locus,the spatially specific activation of As previously mentioned,several BR functions are intricately OsBRD3 in the secondary branch meristems mediates BR linked with the activities of other phytohormones.This sec- inactivation,thereby promoting the accumulation of OsGSK2 tion will provide a more in-depth review of the crosstalk be OsGSK2 then phosphorylates and stabilizes the transcription tween BRs and other phytohormones.Given the observed factor OsMADS1,which in turn activates OsRCN2 (RICE research imbalance among different traits,this section will CENTRORADIAL/S2).OsRCN2 prolongs meristem transition, primarily focus on those traits for which significant evidence thereby enhancing panicle branching and increasing grain of hormonal crosstalk regulation exists.Furthermore,the number.Importantly,this process increases grain number regulation of stress responses by BR-hormone interactions without negatively affecting grain size.The tissue-specific in- will also be discussed. hibition of BRs balances the trade-off between grain number and grain size,offering significant potential for boosting grain Plant height productivity (Zhang et al.,2024).New evidence suggests that Brassinosteroids function in concert with other phyto the OsFAD1-OsMYBR22 module may bind to the structural hormones such as GAs,auxin,ABA and JAs to coordinate variation region of OsCL,thereby modulating the expression of plant height(Figure 2).Among these,GAs are key regulators OsBRD3 (Cheng et al.,2024). of plant stature.BRs engage in a tissue-specific and Furthermore,a quantitative trait locus (QTL)named concentration-dependent interplay with GAs.Under physio- OsSGDP7(SMALL GRAIN AND DENSE PANICLE 7)has been logical conditions,BRs enhance GA levels and cell elongation identified,which is caused by copy number variants(CNVs)in by activating the GA biosynthesis gene OsGA3ox-2 and in- the upstream regulatory region of OsFZP(FRIZZY PANICLE) hibiting the GA inactivation gene OsGA2ox-3.However,high (Bai et al.,2017).OsFZP encodes a member of the APETALA2/ levels of BRs induce GA inactivation via OsGA20x-3 and ethylene response factor(AP2/ERF)transcription factor family inhibit their own biosynthesis in a feedback mechanism, and represses the formation of axillary meristems (Komatsu leading to reduced GA and BR levels and suppressed cell et al.,2003).An 18-bp fragment insertion upstream of OsFZP elongation (Tong et al.,2014).It should be noted that this leads to a tandem duplication that functions as an upstream interaction mechanism is specific in certain tissues at certain silencer.OsBZR1 binds to this region to repress OsFZP stages and may not apply to other traits in other species expression,resulting in increased number of spikelets per (Tong and Chu,2016).Research in maize (Zea mays)also panicle and higher grain yield(Bai et al.,2017). suggests that the interaction between BRs and GAs is context-dependent,exhibiting an additive effect on the Brassinosteroid regulation of grain weight regulation of plant height(Best et al.,2016). Grain weight is primarily determined by grain size and the A recent study in wheat(Triticum aestivum)has revealed extent of grain filling.Given the crucial role of BRs in cell that the deletion of a natural r-e-z haploblock-comprising 568 March 2025 Volume 67 Issue 3 563-581 www.jipb.net Journal of Integrative Plant Biology BR-centric hormone crosstalk OsDCL3a.----BRs Auxin (TaZnF-B) H(TaBKI1 LOsDS1 OsBRI1 OsARF TaBRI1 1/11/17 OsIAA1 ABA·--OsbZIP23 (OsREM4. OSSERK1 OsGSK② TaGSK3 Mesocotyl elongation OsCYC U2 OsmiR159 JAs ZmMYC2 OsBZR1 OsDLT OsSMOS1 OSGAMYBL2 ZmBZR1 (OsOFP1 ZmXTH1 OsDCL3a OsGA2ox-3 OsGA30x-2 OsCPS1 OsPHI-1) GAs Figure 2.Crosstalk between brassinosteroids(BRs)and other phytohormones in regulating plant height Under physiological conditions,BRs promote cell elongation and plant height by either increasing the levels of gibberellins(GAs)or by activating cell wall- related genes such as ZmXTH1 and OsPHI-1,while also engaging in extensive crosstalk with signaling components from other phytohormone pathways. Additionally,BRs modulate cell division and mesocotyl elongation through a coordinated interaction with strigolactones(SLs).Arrows indicate positive regulation,while lines ending with perpendicular bars represent suppressive regulation.Dashed lines indicate indirect mechanisms.ABA,abscisic acid: JAs,jasmonates. TaRht-B1,TaEamA-B,and TaZnF-B-has played a significant DWARF1).These genes regulate plant height,grain size,and role in developing high-yield semi-dwarf wheat varieties. heat tolerance through ubiquitination-mediated stability control Molecular genetics studies further show that knocking of OsBRl1,OsTT3.2,or SiBRI1.This suggests that BRs may out TaRht-B1,a gain-of-function variant of TaDELLA that re- influence agronomic traits by mediating diverse signaling presses GA signaling,results in increased plant height pathways across different species(Zhu et al,2021;Zhang et al., compared to Fielder,the control variety containing the 2022a;Li et al.,2023;Tang et al.,2023). TaRht-B1b allele.In contrast,deletion of TaZnF-B,which Some other components of the BR signaling pathway are encodes a RING-type E3 ligase responsible for mediating implicated with the GA pathway,collectively contributing to TaBKl1 (BRI1 KINASE INHIBITOR1)degradation,leads to the regulation of plant height.For example,wheat TaGSK3 reduced plant height.The double mutant exhibits a semi-dwarf interacts with and phosphorylates TaRht-B1b,enhancing its plant height similar to Fielder,indicating the potential for coor- stability and activity to reduce plant height(Dong et al.,2023). dinating BR and GA pathways in designing semi-dwarf crops Additionally,OsDLT modulates the expression of genes (Song et al,2023;Tong and Chu,2023).Interestingly,the ho- involved in GA metabolism and increases endogenous GA mologous gene of TaZnF-B in rice is OsDGS1 (DECREASED levels (Li et al.,2010).OsOFP1 works in conjunction with GRAIN SIZE1)/OSTT3.1 (THERMO-TOLERANCE 3.1),and in OsDLT to regulate plant height by targeting downstream GA foxtail millet (Setaria italic)it is SiSGD1 (SMALL GRAIN AND metabolism genes in rice (Xiao et al.,2017).Another OFP www.jipb.net March 2025 Volume 67 Issue 3 563-581 569 BR-centric hormone crosstalk Journal of Integrative Plant Biology family member,OsOFP22,is involved in repressing both phosphorylation of OsREM4.1 by OsBRI1,which facilitates BR and GA signaling to control plant architecture (Chen the dissociation of OsREM4.1 from OsSERK1 and thereby etal.,2021). initiates BR signaling(Gui et al.,2016). Small RNAs,including microRNAs (miRNAs)and small Jasmonic acids also antagonize BRs in the regulation of interfering RNAs (siRNAs),play a crucial role in mediating internode elongation in maize.Application of JA mimic cor- the interactions between BRs and GAs.OsBZR1 directly onatine (COR)activates the JA downstream transcription activates the expression of OsmiR396d,which in tum factors ZmMYC2-4 and ZmMYC2-6.These ZmMYC2 tran- suppresses GA biosynthesis and signaling by targeted scription factors interact with ZmBZR1,releasing the in- cleaving of the OsGRF6 transcript.Consequently,over- hibition on Zm/BH7 expression.ZmlBH1 then forms a het- expression of OsmiR396d in rice leads to a reduction in plant erodimer with ZmbHLH154,which subsequently reduces the height (Tang et al.,2018).Additionally,the BR-responsive formation and transcriptional activity of ZmbHLH154 homo- module OsmiR159d-OsGAMYBL2 represses OsBU1 (BR dimers by directly binding to the promoter region of the cell UPREGULATED1)in BR signaling and OsCPS1 and wall-related gene ZmXTH1 (XYLOGLUCAN ENDO- OsGA3ox-2 in GA biosynthesis (Gao et al.,2018).Moreover, TRANSGLUCOSYLASE/HYDROLASE 1),thereby attenuating deficiency in the rice Dicer-like 3 homolog OsDCL3a leads to cell elongation and internode growth(Wang et al.,2024b). reduced levels of 24-nt siRNAs and directly impacts the ex- Under conditions of deep direct seeding and mechanized pression of genes involved in GA and BR homeostasis, dry seeding,BRs and SLs exhibit antagonistic effects on thereby influencing various agricultural traits such as plant mesocotyl elongation,a process crucial for propelling buds height and leaf angle(Wei et al.,2014). above the soil or water surface.Brassinosteroids inhibit the One of the impacts of auxin interaction with BRs is the phosphorylation of OsCYC U2,a U-type cyclin that drives modulation on BR perception.Auxin response factors (ARFs), mesocotyl growth through cell cycle regulation,by sup- which are transcription factors in auxin signaling,bind to the pressing the activity of OsGSK2,thus promoting mesocotyl auxin response element (AuxRE in the OsBR/1 promoter, elongation.Conversely,SLs are perceived by the receptor thereby activating its expression.For instance,OsARF11 and OsD14,which subsequently interacts with OsD3 and forms OsARF17 regulate rice development by directly activating the OsSCF E3 ubiquitin ligase complex.This complex pro- OsBR/1 (Sakamoto et al.,2013;Lan et al.,2023).Additionally motes the degradation of OsGSK2-phosphorylated OsCYC OsDS1 (DWARF AND SMALL GRAIN 1)/OsEMF1(EMBRYONIC U2 to inhibit mesocotyl length(Sun et al.,2018). FLOWER 1)collaborates with OsARF11 to co-regulate OsBR/1 transcription (Liu et al.,2018).Moreover,OslAA1,a member of Leaf angle the Aux/IAA (auxin/indole acetic acid)family and an inhibitor of Several lines of evidence suggest that phytohormones such OsARF1,is involved in the crosstalk between auxin and BR as auxin,ABA,JAs,and ethylene may regulate leaf angle,at pathway,likely through the regulation of OsARF1 on BR signaling least partially,through crosstalk with the BR pathway components such as OsBR/1(Song et al.,2009).Collectively,the (Figure 3).Although exogenous auxin has been shown to OsIAA-OsARF module directly impacts BR signaling by modu- slightly promote leaf bending (Wada et al.,1981),recent lating OsBR/1 expression,thereby affecting various plant traits, genetic studies have revealed that auxin actually plays a including plant height,grain size,and leaf angle. negative role in the regulation of leaf angle.As mentioned Additionally,OsSMOS1,a target of OsGSK2,also serves above,auxin and BR pathways are linked through both the as an auxin-responsive transcription factor of the AP2-type OsIAA-OsARF-OsBR/1 signaling cascade and the OsBZR1- (Aya et al.,2014).The transcriptional complex OsBZR1- OsSMOS1-OsDLT transcriptional complex,which also im- OsSMOS1-OsDLT cooperatively enhances the transcription pact leaf angle.Additionally,OsARF19,a negative regulator of target genes such as OsPH/-1,promoting cell elongation. in auxin signaling,enhances leaf angle by directly activating This complex links BR and auxin signaling to coordinate the the expression of OsBR/1 and OsGH3-5,which encodes an size of various organs,including those related to plant height, indole-3-acetic acid-amido synthetase for reducing free grain size and leaf angle (Hirano et al.,2017;Qiao et al., auxin levels,thus bridging auxin and BR signaling in the 2017).Moreover,physiological assays in soybean (Glycine regulation of leaf angle (Zhang et al.,2015).Moreover, max)indicate that BRs and auxin synergistically promote OsARF4 has been reported to suppress leaf inclination in shade-induced hypocotyl elongation,while GAs act down- rice.Transcriptome analysis has revealed changes in BR stream in the signaling pathway(Jiang et al.,2020). biosynthesis and response genes in OsARF4 transgenic Abscisic acid and BRs exhibit antagonistic interactions in plants(Qiao et al.,2022).Similarly,in tomato (Solanum /y- various developmental processes,including the modulation copersicum),SIARF11,homologous to OsARF11,promotes of plant height,leaf angle,and grain size.ABA promotes the leaf angle by activating genes related to auxin and BRs expression of the rice remorin gene OsREM4.1 via the tran- (Wang et al.,2024a).Furthermore,OsP/N1b,which encodes scriptional activator OsbZIP23 and enhances the interactions an auxin efflux carrier protein,responds to both BRs and between OsREM4.1 and OsSERK1.This interaction blocks auxin signaling,suggesting that OsPIN1b promotes lamina BR signaling by preventing the assembly of the OsBRl1- inclination through interplay of these two pathways(Zhang OsSERK1 receptor complex.Conversely,BRs induce the etal.,2023) 570 March 2025 Volume 67 Issue 3 563-581 www.jipb.net Journal of Integrative Plant Biology BR-centric hormone crosstalk with transcriptional repression activity,as a negative regulator of lamina joint bending.OsLPA1 was shown to repress auxin sig- GAs naling and interact with C-22-hydroxylated and 6-deoxo BRs in OsSHI1 an OsBRl1-independent manner(Liu et al.,2016a).The role of ABA OsSLR1 (OSSPY) OsLPA1 is further supported by observations that maize mutants Auxin lacking the ZmLPA1 gene exhibit increased leaf angles (Ji et al., 2024).These findings collectively imply that exogenous auxin (OsGSR1 →(OsBRD2 may promote leaf angle through a BR pathway that operates independently of OsBRI1. BRS Physiological studies have uncovered that both ABA and MeJA(methyl jasmonate)decrease leaf angle and counteract OsbZIP23 OsREM4.1 OsARF1/11/19 the increase in leaf angle induced by BRs,suggesting an (OsBRI1 TaARF6 antagonistic relationship between these phytohormones and (OsSERK1 BRs in the control of leaf inclination.Further genetic analyses Ethylene reveal that ABA or MeJA repress BR biosynthesis and sig- naling pathways in rice (Gan et al.,2015;Li et al.,2019). (OsSMOS1 TaSPL8) Additionally,the ABA-responsive factor OsREM4.1 negatively OsDLT regulates the initiation of BR signaling,thereby enhancing JAs ---- leaf erectness (Gui et al.,2016).Intriguingly,at low concen- OsBZR1 trations,ABA can increase leaf angle through a synergistic interaction with BRs.The master transcription factor OsABI3 in ABA signaling transiently induces the expression of OsGSR1 (also known as OsGW6/OsGASR7),a member of the gene family encoding GA-stimulated transcript (GAST) proteins,which in tum activates the BR biosynthetic gene OsBRD2 (Wang et al.,2009),leading to a temporary accumu- Figure 3.Crosstalk between brassinosteroids (BRs)and other lation of BRs and a consequent widening of the leaf angle phytohormones in regulating leaf angle Hormones such as auxin,abscisic acid(ABA),gibberellins (GA),jasmo (Li et al.,2021).In addition to OsGSR1,another component in GA nates(JAs),and ethylene are proposed to influence leaf angle,at least in signaling,OsSPY (SPINDLY)is also implicated in regulating leaf part,through their interactions with the BR pathway.Notably,auxin also angle by influencing BR response in rice(Shimada et al.,2006). exerts a negative role in the regulation of leaf angle independently of BRs. Studies in Arabidopsis show that AtSPY encodes an Arrows indicate positive regulation,while lines ending with perpendicular bars represent suppressive regulation.Dashed lines indicate indirect O-fucosyltransferase that catalyzes the O-fucosylation of the mechanisms. AtDELLA protein.This post-translational modification activates AtDELLA by enhancing its interaction with AtBZR1,thereby in- In addition,BR signaling components also modulate auxin hibiting AtBZR1 ability to bind DNA and regulate transcription signaling in leaf angle control.OsBZR1 directly binds to the (Bai et al.,2012;Zentella et al.,2017).Given the similar pheno- BR-responsive element (BRRE)in the Os/AA6 promoter to types observed in spy mutants of both Arabidopsis and rice,it is stimulate its transcription.OsIAA6 in tum suppresses auxin possible that OsSPY may share a conserved function in re signaling via interacting with and inhibiting the activity of pressing BR signaling in rice.Furthermore,knocking down OsARF1,thereby increasing leaf angle (Xing et al.,2022). OsSPY leads to elevated BR levels in rice(Shimada et al.,2006), TaSPL8,a SQUAMOSA PROMOTER BINDING-LIKE protein, suggesting that OsSPY also plays a role in negatively regulating binds to the promoters of TaARF6 and TaD2,and thus acti- BR biosynthesis,directly or indirectly by modulating the activity vates auxin signaling and BR biosynthesis pathways to or stability of BR metabolic enzymes. modulate leaf angle in wheat(Liu et al.,2019).ZmbHLH112,a The increase in leaf angle induced by BRs is impeded by basic helix-loop-helix (bHLH)transcription factor,regulates cobalt chloride(CoCl2),an inhibitor of 1-aminocyclopropane- leaf angle through auxin and BR signaling in maize(Zhang 1-carboxylate(ACC)oxidase (ACO),indicating crosstalk be etal.,2022b). tween ethylene and BRs in the regulation of leaf angle(Cao In contrast to the generally inhibitory role of auxin in leaf angle and Chen,1995).However,the molecular mechanism un- regulation,the exogenous application of auxin can also synerg- derlying the interaction between ethylene and BRs in regu- istically interact with BRs to promote larger leaf angles (Takeno lating leaf angle remains unclear. and Pharis,1982).It has been indicated that auxin signaling Several regulatory factors integrate various phytohormone requires C-22-hydroxylated BRs to induce lamina joint pathways to control leaf angle.The short intemode1 (shi1) bending,and this process operates independently of the OsBRI1 mutant displays characteristics typical of BR deficiency,such signaling pathway (Nakamura et al.,2009).Additionally,a sub- as erect leaves and small grains,alongside traits associated sequent study identified OsLPA1 (LOOSE PLANT ARCHI- with auxin and ABA.OsSH/1 encodes a transcription factor TECTURE1),a plant-specific INDETERMINATE DOMAIN protein that coordinates the biosynthesis of auxin,BRs,and ABA www.jipb.net March 2025 Volume 67 Issue 3 563-581 571 BR-centric hormone crosstalk Journal of Integrative Plant Biology signaling transduction.In turn,these phytohormones finely regulate the expression of OsSH/7,indicating that OsSHI1 functions as a central hub integrating various hormone sig- OsGSR1 OsBRD2 nals to orchestrate rice growth and stress tolerance (Duan ABA et al.,2023).In cotton (Gossypium hirsutum),GhAPC8,a component of the RING E3 ubiquitin ligase complex,influ- ences leaf angle by modulating the biosynthesis and sig- GAs BRs OsbZIP23 naling of phytohormones,including BRs,GAs,and auxin (Jin et al.,2022).Similarly,in maize,ZmCLA4 functions as a Cell expansion transcriptional repressor that links multiple phytohormone OsREM4.1 (OsBRI1 signaling pathways including BRs,auxin,ABA,and JA in OsmiR159 (OSSERK1 regulating leaf angle(Dou et al.,2021). Auxin Cytokinins Tiller number OsGAMYBL2 Brassinosteroids regulate rice tillering through interactions OsIAA10 OSPPKL1) with both the SL and GA pathways.The BR signaling com- OsmiR167 plex,OsBZR1-OsSMOS1-OsDLT,plays a pivotal role in OsHKs /OsARF suppressing the expression of OsFC1/0s7B1,a negative 4/12/17 OsGSK2/5 regulator of tiller bud outgrowth,through direct binding by OsBZR1.Additionally,OsD53,a key transcriptional repressor P Cell proliferation OsAHP2 in SL signaling,is recruited by OsBZR1 to cooperatively in- expansion (OsSMOS1 hibit the expression of OsFC1.The interaction between BRs 31/0 and SLs is antagonistic,affecting the assembly of the Ethylene OsDLT OsBZR1-OsD53 complex and thereby regulating tillering in rice (Fang et al.,2020). OsBZR1 Furthermore,OsNGR5 (NITROGEN-MEDIATED TILLER OsERF115 Cell proliferation GROWTH RESPONSE 5),an allele of OsSMOS1,regulates Cell proliferation rice tillering response to nitrogen fertilization via GA signaling expansion OsNGR5 competes with OsGID1 for interaction with the OsDELLA protein.In Green Revolution varieties,accumu- lated OsDELLA stabilizes OsNGR5 by inhibiting its degra- Figure 4.Crosstalk between brassinosteroids (BRs)and other phytohormones in regulating grain size dation via OsGID1.Under nitrogen supply,OsNGR5 re- Brassinosteroids interact with other phytohormones to coordinately con- presses the expression of shoot branching-inhibitory genes trol grain size by modulating cell proliferation and expansion throughout by recruiting polycomb repressive complex 2(PRC2)to me the grain development process.Arrows indicate positive regulation,while diate trimethylation of histone H3 lysine 27(H3K27me3),thus lines ending with perpendicular bars represent suppressive regulation. promoting tillering (Wu et al.,2020). Dashed lines denote indirect mechanisms.ABA,abscisic acid;GA, gibberellins. Grain size stabilizes OsARF4,and both proteins repress a common set Grain size is regulated by a complex interplay of BRs with various of target genes(Hu et al.,2018).A recent study has revealed phytohormones,including auxin,cytokinins,ABA,GAs,and that OsGSK5,as a negative component of BR signaling,in- ethylene.This interaction underscores the intricate genetic net- teracts with and phosphorylates OslAA10.This phosphor- work governing grain development in rice (Figure 4).As ylation promotes the degradation of OsIAA10 by facilitating previously discussed,signaling cascades such as OslAA- its interaction with OsTIR1,while inhibiting its interaction OsARF-OsBR/1 and OsmiR159d-OsGAMYBL2,as well as regu- with OsARF4.This release of OsARF4's regulatory effect latory complexes such as OsBZR1-OsSMOS1-OsDLT and allows for the repression of downstream genes such as OsREM4.1-OsSERK1,are crucial not only for controlling plant OsPH/-1 (Ma et al.,2023).Collectively,these findings high- height and leaf angle but also for modulating grain size. light the interdependent roles of BRs and auxin in controlling In the regulation of grain size,OsGAMYBL2 binds to the grain size. promoter of OsmiR167,enhancing its expression.OsARF12, In addition to its role in BR signaling,OsPPKL1 is crucial in a primary target of OsmiR167,plays a significant role in grain regulating grain size by modulating cytokinin signaling,in- filling and grain size regulation by mediating auxin and BR dependent of its phosphatase activity,which is essential for signaling and promoting cell division through the stimulation BR signaling.Cytokinin signal is transduced through a histi. of OsCDKF;2,a cyclin-dependent kinase gene (Zhao et al., dine(H)-aspartic acid (D)phosphorelay pathway,which in 2023).Additionally,OsGSK5 has been identified as a key volves the transfer of phosphate groups from histidine kin- negative regulator of grain size in rice(Hu et al.,2018;Xia ases (HKs)to histidine phosphotransfer proteins (HPs),and et al.,2018;Ying et al.,2018).OsGSK5 phosphorylates and subsequently to response regulators (RRs).Notably,a 572 March 2025 Volume 67 Issue 3 563-581 www.jipb.net“油菜素内酯”情境下的 植物生命活动调节复习课 高中生物组 庄浩宇 高三生物二轮复习 试题回顾 14. 【福建省七地市2026届高中毕业班模拟测试】研究发现，低温可诱导菊花CmbZIP19基因的表达量增加，影响侧枝伸长。为研究CmbZIP19基因的相关作用机制，研究人员用野生型菊花(WT)、CmbZIP19基因缺失突变体(ami)和CmbZIP19基因过表达突变体(OX)为材料，检测植株的侧枝长度、内源油菜素内酯(BR)含量，结果见下图。下列叙述错误的是（ ） A. 温度可作为信号调控CmbZIP19基因的表达 B. CmbZIP19基因表达增强会抑制菊花侧枝伸长 C. CmbZIP19基因表达可提高菊花内源BR含量 D. 寒冷条件下可通过喷施BR促进菊花侧枝伸长 【选必一 P97】科学家发现，除了上述五类植物激素，植物体内还有一些天然物质也起到调节生长发育的作用。其中，油菜素内酯已经被正式认定为第六类植物激素。 2 油菜素内酯(BR)有何作用？ 提示见备注 单位面积的谷粒产量由三个组成特征决定：单产穗数（主要取决于株型）、粒数每穗和粒重。水稻中的植物结构主要与农艺性状相关，包括植株高度、叶片角度和分蘗[niè]（禾本科植物在地面以下或近地面处产生的分枝现象）数。 BRs促进节间细胞伸长以增加植株高度。BRs通过抑制背面的厚壁细胞增殖，促进正面的厚壁细胞增殖来增加叶片角度细胞扩张，抑制厚质细胞内木质素沉积。 BRs促进分蘖（禾本科植物在地面以下或近地面处产生的分枝现象）芽生长，正向调节分蘖数。组织特异性BR抑制增强穗状分枝和每锥锥的粒数。 BRs通过促进细胞扩张、细胞增殖和谷粒灌浆来增加粒重。 【备注】引自文献《Understanding brassinosteroid-centric phytohormone interactions for crop improvement（Wenchao Yin, Nana Dong, Xicheng Li, Yanzhao Yang, Zefu Lu, Wenbin Zhou, Qian Qian, Chengcai Chu, Hongning Tong）》原文见“参考文献1” 3 探究油菜素内酯的运输方式 【回顾】物质跨膜运输的方式有哪些？ 油菜素内酯在细胞内合成。观察其结构，发现其含有多个亲水基团，因此我们可以推测油菜素内酯可能难以通过_________________的方式运出细胞。 方式一：自由扩散（气体、小分子物质） 方式二：协助扩散（主动运输【逆浓度梯度、耗能】和 被动运输【顺浓度梯度、不耗能】） 方式三：胞吞、胞吐（大分子物质、神经递质） 自由扩散 探究油菜素内酯的运输方式 为研究油菜素内酯的跨膜运输机制，科研人员进行了如下实验。 实验一：ABCB19过去被认为是运输生长素的转运蛋白，但对ABCB19蛋白突变体植株进行培育，发现其表型与其他的生长素运输蛋白突变体表现出明显差异。 实验二：为探究ABCB19的底物特异性，用纯化的ABCB19分别与生长素（IAA）、赤霉素（GA）、BL在适宜条件下混合，加入足量ATP后，测定各组ATP酶活性，结果见图1。 探究油菜素内酯的运输方式 ABCB19蛋白具有ATP酶活性，与底物结合时会被激活，ATP酶活性可以反映ABCB19的活性。 图1结果表明： 结合实验一和二的结果，提出关于转运蛋白ABCB19的假说： ABCB19可与油菜素内酯发生特异性结合 ABCB19能通过主动运输转运油菜素内酯 探究油菜素内酯的运输方式 为验证上述假说，科研人员利用3H标记的BL、脂质体WT和EQ、ATP、ATP酶抑制剂等进行转运实验。请根据图2的结果，补全实验设计表格。 分组 脂质体 3H-BL ATP ATP酶抑制剂 甲 __________ + + __________ 乙 WT + + __________ 丙 EQ + + - 丁 __________ + + + 注：WT为含ABCB19蛋白的脂质体，EQ为含突变型ABCB19蛋白的脂质体，突变型ABCB19蛋白不具有ATP酶活性；+表示添加，-表示不添加 WT - + EQ 探究油菜素内酯与其他植物激素的作用 Ⅰ. 探究油菜素内酯（BR）和生长素对于侧根形成的作用 第一步：取生长状况相同的拟南芥幼苗若干，随机均分为10组； 第二步：配置含 0nmol・L-1、 1nmol・L-1、5nmol·L-1、20nmol・L-1 及 50nmol・L-1 的 IAA 琼脂培养基各 2份，其中一份中均加入 1nmol・L-1BL，另一份中均不加； 第三步；将拟南芥幼苗放入上述各培养基，在相同且适宜的条件下培养； 第四步：8 天后，统计各组拟南芥幼苗的每厘米初生根上侧根的 数目并计算百分比（100%，水平虚线），得到图 1 所示的实验 结果。 （1）实验的自变量是？ （2）图中 AB 两点对照可得出的结论？ IAA的浓度、1nmol・L-1BL的有无 1nmol・L-1BL对侧根的形成有促进作用 探究油菜素内酯与其他植物激素的作用 Ⅱ. 探究油菜素内酯（BR）和赤霉素作用 棉花纤维长度直接关系到纤维在纺织工业的加工应用，下图揭示了BR（油菜素内酯）信号调控棉纤维伸长的新机制。 据图可知，当BR浓度升高时，激活位于细胞质膜上的_______________，抑制BIN2酶活性从而使转录因子BZR1不被降解失活，经信息传递系统传导到_______________内，激活BR调控基因的表达。 BZR1转录因子是BR合成通路中的核心元件，转录因子的过度表达会导致根毛长度缩短，这是一种_______________调节机制。 探究油菜素内酯与其他植物激素的作用 Ⅱ. 探究油菜素内酯（BR）和赤霉素作用 相关研究表明BR与GA（赤霉素）均能促进棉花纤维伸长，为进一步探究二者在促进纤维伸长方面的相互作用，科研人员做了相关实验。 【实验材料的处理与准备】采集陆地棉开花当天或后一天的花朵，剥离胚珠，整个过程需要在①________条件下操作；取80个生长良好的胚珠，② ________分成四组。 【实验过程】用浓度和用量均适宜的实验试剂处理各组实验材料 实验一：a组用BR处理、b组用GA处理、c组用BR+GA处理（结果如图1） 实验二：a组用GA处理、b组用BR+GA处理、c组用GA+PAC处理、d组用GA+PAC+BR处理（结果如图2）。 一般在做正式实验前要先做预实验，其目的是③ ________实验过程中若使用的试剂浓度较高，常采用④ ________法处理实验材料。 探究油菜素内酯与其他植物激素的作用 Ⅱ. 探究油菜素内酯（BR）和赤霉素作用 相关研究表明BR与GA（赤霉素）均能促进棉花纤维伸长，为进一步探究二者在促进纤维伸长方面的相互作用，科研人员做了相关实验。 【实验结果】如图 【实验结论】推测BR和GA在促进棉花纤维伸长方面具有_____________作用； 已知PAC是GA的合成抑制剂，根据实验结果推测BR可能通过_______________进一步 促进细胞伸长。 探究油菜素内酯与其他植物激素的作用 Ⅱ. 探究油菜素内酯（BR）和赤霉素作用 KAO2、GA20Ox1-1和GA20Ox1-2-1是GA合成过程中的关键酶基因，科研人员同时研究了BR对GA转录水平的影响，据下图分析 促进棉花纤维伸长的分子机制可能是 探究油菜素内酯与其他植物激素的作用 植物侧芽的生长是内外因素共同调控的结果，内部因素以生长素、细胞分裂素（CK）、独脚金内酯（SL）、油菜素内酯（BR）等激素为核心，通过信号通路和基因表达调控侧芽生长；光照、营养、水分等外部因素通过影响激素合成、运输等，间接调控侧芽生长。据图分析，下列叙述正确的是（ ） A．SL 对侧芽生长的两条信号通路的作用效果相反 B．与 BRC1 相比，光敏色素在植物体内分布更为广泛 C．红光可直接抑制生长素的合成，间接促进侧芽的生长 D．蔗糖含量越多对侧芽生长的抑制作用也就越明显 植物响应盐胁迫和恢复生长的调控机制 土壤中盐含量超出植物耐受范围后，植物生长受到影响，降低农业生产效益。根内皮层和木栓层可抵制盐离子，但大量Na＋通过质膜上的阳离子通道进入根部，对植物生长发育造成不利影响（称为盐胁迫）。根系是最早感受到盐胁迫逆境信号并产生相应生理反应的器官。为保持细胞与外界环境的渗透压平衡，根系通过一系列途径激活细胞膜上的S1蛋白活性，促进根系细胞逆浓度外排Na＋。 油菜素内酯（BR）是植物体内的信号分子，合成于根部，在植物的花粉、种子以及根、茎、叶中都有较低水平的分布。虽然BR在植物体内含量较低，但对主根生长及根系发育过程有重要调节作用。研究发现，BR信号通路的负调控蛋白BIN在植物的抗逆性方面起着重要作用。 【思考】研究者认为BR是植物激素，作出此判断的依据是？ 植物响应盐胁迫和恢复生长的调控机制 当盐胁迫发生时，细胞内产生盐胁迫的信号，细胞膜上蛋白复合物C感知盐胁迫，招募S2至细胞膜并发生磷酸化，磷酸化的S2进而激活S1。同时，BIN与蛋白复合物C相互结合的作用减弱，并从细胞膜上解离，抑制BR调控的下游特定基因转录，抑制植物生长。当盐胁迫信号消失时，蛋白复合物C促进BIN在细胞膜上定位，解除对BR下游特定基因转录的抑制作用，促进植物生长。 该研究揭示了植物平衡生长与应激响应的 分子机制，对理解植物如何在环境胁迫和生长 发育之间保持平衡具有重要意义。 请结合本文撰写一段文字，作为教科书中介绍“其他植物激素的种类和作用”的补充。 植物响应盐胁迫和恢复生长的调控机制 根据材料，下列有关说法错误的是______。 A．盐胁迫时BIN蛋白会完全解除对S2的抑制作用，促进S1酶激活 B．盐胁迫消失，BIN蛋白定位于细胞膜上，增强对S2的抑制作用 C．盐胁迫信号可以调控BIN在细胞中的定位和其调控的分子底物 D．植物通过一定的机制调节，保证在盐胁迫和生长发育之间维持平衡 植物响应盐胁迫和恢复生长的调控机制 小麦是我国重要的粮食作物，盐胁迫严重影响其生长和产量。我国某科研团队对小麦耐盐的分子机制进行了研究，结果如图1所示，图中TaBZR1是油菜素内酯发挥作用过程中所需的一种具有调控转录功能的蛋白质；TaGPX1/2/3/4表示与活性氧相关的基因；“→”表示促进或提高。 （1）除了提高小麦耐盐性以外，脱落酸还具有维持种子休眠，______________________等作用。在调节种子休眠方面，脱落酸与______________________的作用相抗衡。 （2）盐胁迫下，用油菜素内酯抑制剂处理小麦，发现相比较于未用油菜素内酯抑制剂处理组，TaBZR1表达量降低，根据途径1可推测油菜素内酯抑制剂处理后，小麦的耐盐性______________，依据： 植物响应盐胁迫和恢复生长的调控机制 （3）植物中活性氧过度积累会造成细胞膜的损伤。研究人员对盐胁迫下，控制TaBZR1合成基因正常表达和大量表达植株中，TaGPX1/2/3/4基因的表达情况进行了测定，结果如图2所示。根据以上信息，图1中①②③分别是什么？（填“→”或“——|”，表示抑制或降低） （4）基于上述机制，请提出一条培育高耐盐小麦新品种的思路。 $