New Phytol , IF:8.512 , 2020 Feb , V225 (4) : P1516-1530 doi: 10.1111/nph.15936
Brassinosteroid regulation of wood formation in poplar.
College of Life Sciences, Zhejiang University, 866 Yu Hang tang Road, Hangzhou, 310058, China.; State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, 100091, China.; Pacific Southwest Research Station, US Forest Service, Davis, CA, 95618, USA.; State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang Agriculture and Forest University, Hangzhou, 311300, China.; Department of Plant Biology, University of California Davis, Davis, CA, 95616, USA.
Brassinosteroids have been implicated in the differentiation of vascular cell types in herbaceous plants, but their roles during secondary growth and wood formation are not well defined. Here we pharmacologically and genetically manipulated brassinosteroid levels in poplar trees and assayed the effects on secondary growth and wood formation, and on gene expression within stems. Elevated brassinosteroid levels resulted in increases in secondary growth and tension wood formation, while inhibition of brassinosteroid synthesis resulted in decreased growth and secondary vascular differentiation. Analysis of gene expression showed that brassinosteroid action is positively associated with genes involved in cell differentiation and cell-wall biosynthesis. The results presented here show that brassinosteroids play a foundational role in the regulation of secondary growth and wood formation, in part through the regulation of cell differentiation and secondary cell wall biosynthesis.
PMID: 31120133
Curr Opin Plant Biol , IF:8.356 , 2020 Feb , V53 : P90-97 doi: 10.1016/j.pbi.2019.10.008
Growth models from a brassinosteroid perspective.
Faculty of Biology, Technion-Israel Institute of Technology, Haifa 3200003, Israel.; Faculty of Biology, Technion-Israel Institute of Technology, Haifa 3200003, Israel. Electronic address: sigal@technion.ac.il.
Plant growth relies on interconnected hormonal pathways, their corresponding transcriptional networks and mechanical signals. This work reviews recent brassinosteroid (BR) studies and integrates them with current growth models derived from research in roots. The relevance of spatiotemporal BR signaling in the longitudinal and radial root axes and its multifaceted interaction with auxin, the impact of BR on final cell size determination and its interplay with microtubules and the cell wall are discussed. Also highlighted are emerging variations of canonical BR signaling that could function in developmental-specific context.
PMID: 31809963
Plant Physiol , IF:6.902 , 2020 Feb , V182 (2) : P1066-1082 doi: 10.1104/pp.19.01220
Brassinosteroids Antagonize Jasmonate-Activated Plant Defense Responses through BRI1-EMS-SUPPRESSOR1 (BES1).
State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China.; School of Life Sciences, Shandong University, Jinan 250110, China.; State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China xiaoshi3@mail.sysu.edu.cn.
Brassinosteroids (BRs) and jasmonates (JAs) regulate plant growth, development, and defense responses, but how these phytohormones mediate the growth-defense tradeoff is unclear. Here, we identified the Arabidopsis (Arabidopsis thaliana) dwarf at early stages1 (dwe1) mutant, which exhibits enhanced expression of defensin genes PLANT DEFENSIN1.2a (PDF1.2a) and PDF1.2b The dwe1 mutant showed increased resistance to herbivory by beet armyworms (Spodoptera exigua) and infection by botrytis (Botrytis cinerea). DWE1 encodes ROTUNDIFOLIA3, a cytochrome P450 protein essential for BR biosynthesis. The JA-inducible transcription of PDF1.2a and PDF1.2b was significantly reduced in the BRASSINOSTEROID INSENSITIVE1-ETHYL METHANESULFONATE-SUPPRESSOR1 (BES1) gain-of-function mutant bes1- D, which was highly susceptible to S. exigua and B. cinerea BES1 directly targeted the terminator regions of PDF1.2a/PDF1.2b and suppressed their expression. PDF1.2a overexpression diminished the enhanced susceptibility of bes1- D to B. cinerea but did not improve resistance of bes1- D to S. exigua In response to S. exigua herbivory, BES1 inhibited biosynthesis of the JA-induced insect defense-related metabolite indolic glucosinolate by interacting with transcription factors MYB DOMAIN PROTEIN34 (MYB34), MYB51, and MYB122 and suppressing expression of genes encoding CYTOCHROME P450 FAMILY79 SUBFAMILY B POLYPEPTIDE3 (CYP79B3) and UDP-GLUCOSYL TRANSFERASE 74B1 (UGT74B1). Thus, BR contributes to the growth-defense tradeoff by suppressing expression of defensin and glucosinolate biosynthesis genes.
PMID: 31776183
Plant Physiol , IF:6.902 , 2020 Feb , V182 (2) : P892-907 doi: 10.1104/pp.19.00928
Exogenous Auxin Induces Transverse Microtubule Arrays Through TRANSPORT INHIBITOR RESPONSE1/AUXIN SIGNALING F-BOX Receptors.
Department of Biology, Indiana University, Bloomington, Indiana 47405.; Department of Biology, Indiana University, Bloomington, Indiana 47405 SiShaw@Indiana.edu.
Auxin plays a central role in controlling plant cell growth and morphogenesis. Application of auxin to light-grown seedlings elicits both axial growth and transverse patterning of the cortical microtubule cytoskeleton in hypocotyl cells. Microtubules respond to exogenous auxin within 5 min, although repatterning of the array does not initiate until 30 min after application and is complete by 2 h. To examine the requirements for auxin-induced microtubule array patterning, we used an Arabidopsis (Arabidopsis thaliana) double auxin f-box (afb) receptor mutant, afb4-8 afb5-5, that responds to conventional auxin (indole-3-acetic acid) but has a strongly diminished response to the auxin analog, picloram. We show that 5 microm picloram induces immediate changes to microtubule density and later transverse microtubule patterning in wild-type plants, but does not cause microtubule array reorganization in the afb4-8 afb5-5 mutant. Additionally, a dominant mutant (axr2-1) for the auxin coreceptor AUXIN RESPONSIVE2 (AXR2) was strongly suppressed for auxin-induced microtubule array reorganization, providing additional evidence that auxin functions through a transcriptional pathway for transverse patterning. We observed that brassinosteroid application mimicked the auxin response, showing both early and late microtubule array effects, and induced transverse patterning in the axr2-1 mutant. Application of auxin to the brassinosteroid synthesis mutant, diminuto1, induced transverse array patterning but did not produce significant axial growth. Thus, exogenous auxin induces transverse microtubule patterning through the TRANSPORT INHIBITOR 1/AUXIN F-BOX (TIR1/AFB) transcriptional pathway and can act independently of brassinosteroids.
PMID: 31767691
Int J Mol Sci , IF:4.556 , 2020 Feb , V21 (5) doi: 10.3390/ijms21051561
Deviating from the Beaten Track: New Twists in Brassinosteroid Receptor Function.
Centre for Organismal Studies (COS) Heidelberg, INF230, 69120 Heidelberg, Germany.
A key feature of plants is their plastic development tailored to the environmental conditions. To integrate environmental signals with genetic growth regulatory programs, plants rely on a number of hormonal pathways, which are intimately connected at multiple levels. Brassinosteroids (BRs), a class of plant sterol hormones, are perceived by cell surface receptors and trigger responses instrumental in tailoring developmental programs to environmental cues. Arguably, BR signalling is one of the best-characterized plant signalling pathways, and the molecular composition of the core signal transduction cascade seems clear. However, BR research continues to reveal new twists to re-shape our view on this key signalling circuit. Here, exciting novel findings pointing to the plasma membrane as a key site for BR signalling modulation and integration with other pathways are reviewed and new inputs into the BR signalling pathway and emerging "non-canonical" functions of the BR receptor complex are highlighted. Together, this new evidence underscores the complexity of plant signalling integration and serves as a reminder that highly-interconnected signalling pathways frequently comprise non-linear aspects which are difficult to convey in classical conceptual models.
PMID: 32106564
Int J Mol Sci , IF:4.556 , 2020 Feb , V21 (4) doi: 10.3390/ijms21041437
BAK1 Mediates Light Intensity to Phosphorylate and Activate Catalases to Regulate Plant Growth and Development.
State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, China.; Department of Plant Sciences, University of Idaho, Moscow, ID 83844, USA.; Hybrid Rapeseed Research Center of Shaanxi Province, Yangling 712100, Shaanxi, China.
BAK1 (brassinosteroid-insensitive 1 (BRI1) associated receptor kinase 1) plays major roles in multiple signaling pathways as a coreceptor to regulate plant growth and development and stress response. However, the role of BAK1 in high light signaling is still poorly understood. Here we observed that overexpression of BAK1 in Arabidopsis interferes with the function of high light in promoting plant growth and development, which is independent of the brassinosteroid (BR) signaling pathway. Further investigation shows that high light enhances the phosphorylation of BAK1 and catalase activity, thereby reducing hydrogen peroxide (H2O2) accumulation. Catalase3 (CAT3) is identified as a BAK1-interacting protein by affinity purification and LC-MS/MS analysis. Biochemical analysis confirms that BAK1 interacts with and phosphorylates all three catalases (CAT1, CAT2, and CAT3) of the Arabidopsis genome, and the trans-phosphorylation sites of three catalases with BAK1-CD are identified by LC-MS/MS in vitro. Genetic analyses reveal that the BAK1 overexpression plants knocked out all the three CAT genes completely abolishing the effect of BAK1 on suppression of high light-promoted growth. This study first unravels the role of BAK1 in mediating high light-triggered activation of CATs, thereby degrading H2O2 and regulating plant growth and development in Arabidopsis.
PMID: 32093294
Int J Mol Sci , IF:4.556 , 2020 Feb , V21 (4) doi: 10.3390/ijms21041191
The Role of Brassinosteroids in Controlling Plant Height in Poaceae: A Genetic Perspective.
Department of Agricultural and Environmental Sciences-Production, Landscape, Agroenergy (DISAA), Universita degli Studi di Milano, Via Celoria 2, 20133 Milan, Italy.
The most consistent phenotype of the brassinosteroid (BR)-related mutants is the dwarf habit. This observation has been reported in every species in which BR action has been studied through a mutational approach. On this basis, a significant role has been attributed to BRs in promoting plant growth. In this review, we summarize the work conducted in rice, maize, and barley for the genetic dissection of the pathway and the functional analysis of the genes involved. Similarities and differences detected in these species for the BR role in plant development are presented. BR promotes plant cell elongation through a complex signalling cascade that modulates the activities of growth-related genes and through the interaction with gibberellins (GAs), another class of important growth-promoting hormones. Evidence of BR-GA cross-talk in controlling plant height has been collected, and mechanisms of interaction have been studied in detail in Arabidopsis thaliana and in rice (Oryza sativa). The complex picture emerging from the studies has highlighted points of interaction involving both metabolic and signalling pathways. Variations in plant stature influence plant performance in terms of stability and yield. The comprehension of BR's functional mechanisms will therefore be fundamental for future applications in plant-breeding programs.
PMID: 32054028
Int J Mol Sci , IF:4.556 , 2020 Feb , V21 (3) doi: 10.3390/ijms21030996
Maize ZmBES1/BZR1-5 Decreases ABA Sensitivity and Confers Tolerance to Osmotic Stress in Transgenic Arabidopsis.
Key Laboratory of Biology and Genetic Improvement of Maize in Southwest Region, Ministry of Agriculture, Maize Research Institute, Sichuan Agricultural University, Chengdu 611130, China.
The BRI1-EMS suppressor 1 (BES1)/brassinazole-resistant 1 (BZR1) transcription factors, key components in the brassinosteroid signaling pathway, play pivotal roles in plant growth and development. However, the function of BES1/BZR1 in crops during stress response remains poorly understood. In the present study, we characterized ZmBES1/BZR1-5 from maize, which was localized to the nucleus and was responsive to abscisic acid (ABA), salt and drought stresses. Heterologous expression of ZmBES1/BZR1-5 in transgenic Arabidopsis resulted in decreased ABA sensitivity, facilitated shoot growth and root development, and enhanced salt and drought tolerance with lower malondialdehyde (MDA) content and relative electrolyte leakage (REL) under osmotic stress. The RNA sequencing (RNA-seq) analysis revealed that 84 common differentially expressed genes (DEGs) were regulated by ZmBES1/BZR1-5 in transgenic Arabidopsis. Subsequently, gene ontology and KEGG pathway enrichment analyses showed that the DEGs were enriched in response to stress, secondary metabolism and metabolic pathways. Furthermore, 30 DEGs were assigned to stress response and possessed 2-15 E-box elements in their promoters, which could be potentially recognized and bound by ZmBES1/BZR1-5. Taken together, our results reveal that the ZmBES1/BZR1-5 transcription factor positively regulates salt and drought tolerance by binding to E-box to induce the expression of downstream stress-related genes. Therefore, our study contributes to the better understanding of BES1/BZR1 function in the stress response of plants.
PMID: 32028614
Biophys J , IF:3.854 , 2020 Feb , V118 (3) : P698-707 doi: 10.1016/j.bpj.2019.12.026
Structural Consequences of Multisite Phosphorylation in the BAK1 Kinase Domain.
Center for Biophysics & Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois.; Center for Biophysics & Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois; Department of Chemical & Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois; Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois; NIH Center for Macromolecular Modeling and Bioinformatics, University of Illinois at Urbana-Champaign, Urbana, Illinois; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois. Electronic address: diwakar@illinois.edu.
Multisite phosphorylation is an important mechanism of post-translational control of protein kinases. The effects of combinations of possible phosphorylation states on protein kinase activity are difficult to study experimentally because of challenges in isolating a particular phosphorylation state; surprising little effort on this topic has been expended in computational studies. To understand the effects of multisite phosphorylation on the plant protein kinase brassinosteroid insensitive 1-associated kinase 1 (BAK1) conformational ensemble, we performed Gaussian accelerated molecular dynamics simulations on eight BAK1 mod-forms involving phosphorylation of the four activation-loop threonine residues and binding of ATP-Mg(2+). We find that unphosphorylated BAK1 transitions into an inactive conformation with a "cracked" activation loop and with the alphaC helix swung away from the active site. T450 phosphorylation can prevent the activation loop from cracking and keep the alphaC helix in an active-like conformation, whereas phosphorylation of T455 only slightly stabilizes the activation loop. There is a general trend of reduced flexibility in interlobe motion with increased phosphorylation. Interestingly, the alphaC helix is destabilized when the activation loop is fully phosphorylated but is again stabilized with ATP-Mg(2+) bound. Our results provide insight into the mechanism of phosphorylation-controlled BAK1 activation while at the same time represent the first, to our knowledge, comprehensive, comparative study of the effects of combinatorial phosphorylation states on protein kinase conformational dynamics.
PMID: 31962105
Plant Cell Rep , IF:3.825 , 2020 Feb , V39 (2) : P259-271 doi: 10.1007/s00299-019-02489-9
A gain-of-function mutation in Brassinosteroid-insensitive 2 alters Arabidopsis floral organ development by altering auxin levels.
Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China.; Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China. zhdawei@scu.edu.cn.; Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China. hhlin@scu.edu.cn.
KEY MESSAGE: Auxin can alter the fertility of bin2-1 plants and depends on the expression of SHY2. Brassinosteroids (BRs) play important roles in plant growth and developmental processes. By systematically evaluating the phenotypes of BR biosynthesis and BR signaling mutants, researchers have reported that BRs positively regulate floral development. In this study, we found that brassinosteroid-insensitive 2 (bin2-1) and short-hypocotyl 2 (shy2-2) mutants exhibited significantly reduced fertility. These mutants had short inflorescences, decreased floral organ length (short petals, stamens, carpels, and stigmas), and short siliques. Exogenous auxin applications could partially rescue the shortened length of the floral organs and siliques of the bin2-1 mutants. Additional experiments revealed that a lack of SHY2 activity increased the fertility of the bin2-1 mutants. A search for downstream affected genes revealed that auxin influences the expression of ARFs and PINs in the bin2-1 mutants, suggesting that auxin plays a major role in the regulation of bin2-1 plant fertility. Thus, BIN2 plays a role in fertility by affecting auxin levels, mainly by altering the expression of SHY2.
PMID: 31820142
Plant Physiol Biochem , IF:3.72 , 2020 Feb , V147 : P31-42 doi: 10.1016/j.plaphy.2019.12.007
Combined effects of brassinosteroid and kinetin mitigates salinity stress in tomato through the modulation of antioxidant and osmolyte metabolism.
College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, 712100, PR China.; School of Studies in Botany, Jiwaji University, Gwalior, MP, India.; Botany and Microbiology Department, College of Science, King Saudi University, P. O. Box. 2460, Riyadh, 11451, Saudi Arabia.; Botany and Microbiology Department, College of Science, King Saudi University, P. O. Box. 2460, Riyadh, 11451, Saudi Arabia; Department of Botany, S.P. College, Srinagar, 190001, Jammu and Kashmir, India. Electronic address: parvaizbot@yahoo.com.
Salinity stress reduces growth and yield productivity of most crop plants. Potentiality of kinetin (Kn) and epi-brassinolide (EBL), either individually or combinedly in preventing the salinity (100 mM NaCl) stress mediated oxidative damage and photosynthetic inhibition was studied in Solanum lycopersicum. Combined application of Kn and EBL imparted much prominent impact on the growth, photosynthesis and metabolism of antioxidants, osmolytes and secondary metabolites. Synthesis of chlorophylls and carotenoids increased and the photosynthetic parameters like stomatal conductance, intercellular CO2 concentration and net photosynthesis were significantly improved due to application of Kn and EBL. Photosystem II functioning (Fv/Fm), photochemical quenching and electron transport rate (ETR) improved significantly in Kn and EBL treated plants imparting significant decline in salinity induced non-photochemical quenching. Exogenous Kn and EBL effectively prevented the oxidative damage by significantly declining the generation of hydrogen peroxide and superoxide under saline and non-saline conditions as reflected in lowered lipid peroxidation and electrolyte leakage. Reduced oxidative damage in Kn and EBL treated plants was accompanied down-regulation of protease and lipoxygenase concomitant with up-regulation of the antioxidant system and the accumulation of compatible osmolytes. Treatment of Kn and EBL proved effective in enhancing the contents of redox homeostasis, ascorbic acid and reduced glutathione, and the secondary metabolites assisting the enzymatic antioxidant system in combating the salinity stress efficiently. Results suggest that combined application of Kn and EBL regulate growth and photosynthesis in tomato more effectively than their individual application through a probable regulatory crosstalk mechanism.
PMID: 31838316
Plant Sci , IF:3.591 , 2020 Feb , V291 : P110315 doi: 10.1016/j.plantsci.2019.110315
Map-based cloning of qBWT-c12 discovered brassinosteroid-mediated control of organ size in cotton.
National Key Laboratory of Crop Genetic Improvement, College of Plant Sciences & Technology, Huazhong Agricultural University, Wuhan 430070, Hubei, China. Electronic address: mhemud@webmail.hzau.edu.cn.; National Key Laboratory of Crop Genetic Improvement, College of Plant Sciences & Technology, Huazhong Agricultural University, Wuhan 430070, Hubei, China. Electronic address: huangcong@webmail.hzau.edu.cn.; National Key Laboratory of Crop Genetic Improvement, College of Plant Sciences & Technology, Huazhong Agricultural University, Wuhan 430070, Hubei, China. Electronic address: shen@webmail.hzau.edu.cn.; National Key Laboratory of Crop Genetic Improvement, College of Plant Sciences & Technology, Huazhong Agricultural University, Wuhan 430070, Hubei, China. Electronic address: anamhemud@webmail.hzau.edu.cn.; National Key Laboratory of Crop Genetic Improvement, College of Plant Sciences & Technology, Huazhong Agricultural University, Wuhan 430070, Hubei, China. Electronic address: linzhongxu@mail.hzau.edu.cn.
Assuring fiber yield stability is the primary objective for cotton breeders since the world population is on the rise, and the demand for cotton fiber is increasing every year. Thus, enhancing average cotton boll weight (BWT) could improve seed cotton production, and ultimately to increase cotton fiber yield. This study accomplished the map-based cloning of a novel boll weight regulating locus, qBWT-c12, in cotton. Bulk segregation analysis detected linked markers, aided in the detection of a stable BWT regulating locus, qBWT-c12, on Chr12 in a novel boll size mutant, BS41. Progeny evaluation confined the qBWT-c12 to a 0.89cM interval between the AD-A12_07 and AD-FM_44 markers in recombinant derived F3 and F4 populations. Homology mapping detected a 40 bp insertion-deletion (InDel) site in the AD-FM_44 clone sequence situated +341 downstream of GhBRH1_A12, which showed complete linkage to the BWT phenotype. The suppressed expression of GhBRH1_A12 suggested its putative involvement during early boll development events in BS41. Although brassinosteroid (BR) biosynthesis and signaling pathway genes were up regulated in different tissues, but the organ growth was suppressed leading to dwarf plants, smaller leaves, and de-morphed smaller bolls in BS41. Thus, a disruption in the BR signal cascade is anticipated and could be related to lower GhBRH1_A12 expression in BS41.This study firstly reported the genetic dissection of boll size regulation of G. barbadense in G. hirsutum background using map-based cloning of a BWT regulating locus, qBWT-c12. Moreover, it also emphasized the putative role GhBRH1_A12 in regulating BR homeostasis and its potential to modulate plant growth and boll development in cotton.
PMID: 31928681
BMC Plant Biol , IF:3.497 , 2020 Feb , V20 (1) : P76 doi: 10.1186/s12870-020-2277-x
Brassinosteroid signaling may regulate the germination of axillary buds in ratoon rice.
Rice Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, 350019, Fujian, China.; Key Laboratory of Germplasm Innovation and Molecular Breeding of Hybrid Rice for South China, Ministry of Agriculture and Rural Affairs, Fuzhou, 350003, Fujian, China.; Incubator of National Key Laboratory of Germplasm Innovation and Molecular Breeding between Fujian and Ministry of Sciences and Technology, Fuzhou, 350003, Fujian, China.; Fuzhou Branch, National Rice Improvement Center of China, P.R. China, Fuzhou, 350003, Fujian, China.; Fujian Engineering Laboratory of Crop Molecular Breeding, P.R. China, Fuzhou, 350003, Fujian, China.; Fujian Key Laboratory of Rice Molecular Breeding, P.R. China, Fuzhou, 350003, Fujian, China.; Base of South China, State Key Laboratory of Hybrid Rice, P.R. China, Fuzhou, 350003, Fujian, China.; Bureau of Agricultural and Rural Affairs of Youxi County, Sanming, 350108, Fujian, China.; Rice Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, 350019, Fujian, China. huaanxie@163.com.; Key Laboratory of Germplasm Innovation and Molecular Breeding of Hybrid Rice for South China, Ministry of Agriculture and Rural Affairs, Fuzhou, 350003, Fujian, China. huaanxie@163.com.; Incubator of National Key Laboratory of Germplasm Innovation and Molecular Breeding between Fujian and Ministry of Sciences and Technology, Fuzhou, 350003, Fujian, China. huaanxie@163.com.; Fuzhou Branch, National Rice Improvement Center of China, P.R. China, Fuzhou, 350003, Fujian, China. huaanxie@163.com.; Fujian Engineering Laboratory of Crop Molecular Breeding, P.R. China, Fuzhou, 350003, Fujian, China. huaanxie@163.com.; Fujian Key Laboratory of Rice Molecular Breeding, P.R. China, Fuzhou, 350003, Fujian, China. huaanxie@163.com.; Base of South China, State Key Laboratory of Hybrid Rice, P.R. China, Fuzhou, 350003, Fujian, China. huaanxie@163.com.; Rice Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, 350019, Fujian, China. jiangzw1973@163.com.; Rice Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, 350019, Fujian, China. jianfzhang@163.com.; Key Laboratory of Germplasm Innovation and Molecular Breeding of Hybrid Rice for South China, Ministry of Agriculture and Rural Affairs, Fuzhou, 350003, Fujian, China. jianfzhang@163.com.; Incubator of National Key Laboratory of Germplasm Innovation and Molecular Breeding between Fujian and Ministry of Sciences and Technology, Fuzhou, 350003, Fujian, China. jianfzhang@163.com.; Fuzhou Branch, National Rice Improvement Center of China, P.R. China, Fuzhou, 350003, Fujian, China. jianfzhang@163.com.; Fujian Engineering Laboratory of Crop Molecular Breeding, P.R. China, Fuzhou, 350003, Fujian, China. jianfzhang@163.com.; Fujian Key Laboratory of Rice Molecular Breeding, P.R. China, Fuzhou, 350003, Fujian, China. jianfzhang@163.com.; Base of South China, State Key Laboratory of Hybrid Rice, P.R. China, Fuzhou, 350003, Fujian, China. jianfzhang@163.com.
BACKGROUND: Rice ratooning has traditionally been an important component of the rice cropping system in China. However, compared with the rice of the first harvest, few studies on factors effecting ratoon rice yield have been conducted. Because ratoon rice is a one-season rice cultivated using axillary buds that germinate on rice stakes and generate panicles after the first crop's harvest, its production is mainly affected by the growth of axillary buds. The objectives of this study were to evaluate the sprouting mechanism of axillary buds to improve the ratoon rice yield. RESULTS: First, we observed the differentiation and growth dynamics of axillary buds at different nodes of Shanyou 63, and found that they differentiated from bottom to top before the heading of the mother stem, and that they developed very slowly. After heading they differentiated from top to bottom, and the ones on the top, especially the top 2nd node, developed much faster than those at the other nodes. The average length and dry weight of the axillary buds were significantly greater than those at other nodes by the yellow ripe stage, and they differentiated into pistils and stamens by 6 d after the yellow ripe stage. The morphology of vegetative organs from regenerated tillers of Shanyou 63 also suggested the superior growth of the upper buds, which was regulated by hormones, in ratoon rice. Furthermore, a comprehensive proteome map of the rice axillary buds at the top 2nd node before and after the yellow ripe stage was established, and some proteins involved in steroid biosynthesis were significantly increased. Of these, four took part in brassinosteroid (BR) biosynthesis. Thus, BR signaling may play a role in the germination of axillary buds of ratoon rice. CONCLUSIONS: The data provide insights into the molecular mechanisms underlying BR signaling, and may allow researchers to explore further the biological functions of endogenous BRs in the germination of axillary buds of ratoon rice.
PMID: 32059642