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Authors: Tao Zhang, Xinyu Wang, Yanchao Yuan, Shoujie Zhu, Chunying Liu, Yuxi Zhang, Shupeng Gai.
Horticulture Research (2024)
Abstract: "Bud endodormancy in perennial plants is a sophisticated system that adapts to seasonal climatic changes. Growth-promoting signals such as low temperature and gibberellins (GAs) are crucial for facilitating budbreak following endodormancy release (EDR). However, the regulatory mechanisms underlying GA-mediated budbreak in tree peony (Paeonia suffruticosa) remain unclear. In tree peony, the expression of PsmiR159b among three differentially expressed miR159 members was inhibited with the prolonged chilling, and overexpression of PsMIR159b delayed budbreak, whereas silencing PsmiR159b promoted budbreak after dormancy. PsMYB65, a downstream transcription factor in the GA pathway, was induced by prolonged chilling and exogenous GA3 treatments. PsMYB65 was identified as a target of PsmiR159b, and promoted budbreak in tree peony. RNA-seq of PsMYB65-silenced buds revealed significant enrichment in the GO terms regulation of ‘cell cycle’ and ‘DNA replication’ among differentially expressed genes. Yeast one-hybrid and electrophoretic mobility shift assays demonstrated that PsMYB65 directly bound to the promoter of the type-D cyclin gene PsCYCD3;1. Dual-luciferase reporter assay indicated that PsMYB65 positively regulate PsCYCD3;1 expression, suggesting that miR159b-PsMYB65 module contributes to budbreak by influencing the cell cycle. Our findings revealed that the PsmiR159b-PsMYB65 module functioned in budbreak after dormancy by regulating cell proliferation, providing valuable insights into the endodormancy release regulation mechanism."
Authors: Wanmin Wang, Zizhao Xie, Yuanyuan Wu, Ying Sun, Chenghang Zhan, Liang Jin and Junli Huang.
Environmental and Experimental Botany (2024)
Highlights: • OsJAZ6 modulates rice tillering and drought response by integrating JA with GA signaling. • OsJAZ6 controls the tiller bud growth but not formation. • OsJAZ6 interacts with SLR1 to promote its degradation, which further destabilizes MOC1. • OsJAZ6 and SLR1 have opposite functions in regulating rice tiller bud growth and drought tolerance.
Abstract: "Jasmonic acid (JA) plays crucial functions during plant growth and stress response, but its roles and regulatory mechanism in plant branching remain largely unknown. Rice basal branching (tillering) is an essential agronomic trait that affects crop production. Here, we report that OsJAZ6, the repressor of JA signaling, negatively modulates rice tillering and drought stress tolerance. Loss-of-function mutants of OsJAZ6 exhibit a significant increase in tiller number, while OsJAZ6ΔJas-overexpression lines produce fewer tillers than wild-type plants. Further investigations show that function loss of OsJAZ6 promotes the tiller bud growth rather than formation. Mechanistic studies show that OsJAZ6 interacts with rice DELLA/SLR1 (SLENDER RICE 1), a transcription repressor of gibberellin (GA) signaling, and the interaction promotes SLR1 degradation, which further facilitates the degradation of rice tillering regulator MOC1 (MONOCULM 1), thereby inhibiting the tiller bud growth. In agreement, the slr1 mutant exhibits fewer tillers than wild type. Consistently, application of JA promotes the growth of tiller bud and thus increases the tiller number, while GA treatment results in opposite result. Meanwhile, osjaz6 mutants display enhanced drought tolerance, coupled with increased JA sensitivity, while the slr1 mutant shows the reverse behavior. Collectively, our data demonstrate that OsJAZ6 negatively modulates rice tillering as well as drought stress tolerance by destabilizing SLR1 protein. Our data shed light on the regulatory mechanism of controlling the tiller development and drought stress response in rice by the JA-OsJAZ6-SLR1 module."
Authors: Yafan Han, Minghao Qu, Zhongchi Liu and Chunying Kang.
The Plant Cell (2024)
One-sentence summary: An MYB transcription factor directly regulates cytokinin homeostasis to repress axillary bud growth and consequently affect crown formation in woodland strawberry.
Abstract: "Shoot branching affects plant architecture. In strawberry (Fragaria L.), short branches (crowns) develop from dormant axillary buds to form inflorescences and flowers. While this developmental transition contributes greatly to perenniality and yield in strawberry, its regulatory mechanism remains unclear and understudied. In the woodland strawberry (Fragaria vesca), we identified and characterized two independent mutants showing more crowns. Both mutant alleles reside in FveMYB117a, a R2R3-MYB transcription factor gene highly expressed in shoot apical meristems, axillary buds and young leaves. Transcriptome analysis revealed that the expression of several cytokinin pathway genes was altered in the fvemyb117a mutant. Consistently, active cytokinins were significantly increased in the axillary buds of the fvemyb117a mutant. Exogenous application of cytokinin enhanced crown outgrowth in the wild type, whereas the cytokinin inhibitors suppressed crown outgrowth in the fvemyb117a mutant. FveMYB117a binds directly to the promoters of the cytokinin homeostasis genes FveIPT2 encoding an isopentenyltransferase and FveCKX1 encoding a cytokinin oxidase to regulate their expression. Conversely, the type-B Arabidopsis response regulators FveARR1 and FveARR2b can directly inhibit the expression of FveMYB117a, indicative of a negative feedback regulation. In conclusion, we identified FveMYB117a as a key repressor of crown outgrowth by inhibiting cytokinin accumulation and provide a mechanistic basis for bud fate transition in an herbaceous perennial plant."
Authors: Zoe Nahas, Fabrizio Ticchiarelli, Martin van Rongen, Jean Dillon and Ottoline Leyser.
New Phytologist (2024)
Abstract: "Arabidopsis thaliana (Arabidopsis) shoot architecture is largely determined by the pattern of axillary buds that grow into lateral branches, the regulation of which requires integrating both local and systemic signals. Nodal explants – stem explants each bearing one leaf and its associated axillary bud – are a simplified system to understand the regulation of bud activation. To explore signal integration in bud activation, we characterised the growth dynamics of buds in nodal explants in key mutants and under different treatments. We observed that isolated axillary buds activate in two genetically and physiologically separable phases: a slow-growing lag phase, followed by a switch to rapid outgrowth. Modifying BRANCHED1 expression or the properties of the auxin transport network, including via strigolactone application, changed the length of the lag phase. While most interventions affected only the length of the lag phase, strigolactone treatment and a second bud also affected the rapid growth phase. Our results are consistent with the hypothesis that the slow-growing lag phase corresponds to the time during which buds establish canalised auxin transport out of the bud, after which they enter a rapid growth phase. Our work also hints at a role for auxin transport in influencing the maximum growth rate of branches."
Authors: Yongfeng Gao, Zihao Chen, Qian Feng, Tao Long, Jihua Ding, Peng Shu, Heng Deng, Peizhi Yu, Wenrong Tan, Siqin Liu, Lucas Gutierrez Rodriguez, Lijun Wang, Víctor Resco de Dios and Yinan Yao.
The Plant Cell (2024)
Abstract: "Photoperiod is a crucial environmental cue for phenological responses, including growth cessation and winter dormancy in perennial woody plants. Two regulatory modules within the photoperiod pathway explain bud dormancy induction in poplar (Populus spp.): the circadian oscillator LATE ELONGATED HYPOCOTYL 2 (LHY2) and GIGANTEA-like genes (GIs) both regulate the key target for winter dormancy induction FLOWERING LOCUS T2 (FT2). However, modification of LHY2 and GIs cannot completely prevent growth cessation and bud set under short-day conditions, indicating that additional regulatory modules are likely involved. We identified PtoHY5a, an orthologs of the photomorphogenesis regulatory factor ELONGATED HYPOCOTYL 5 (HY5) in poplar (Populus tomentosa), that directly activates PtoFT2 expression and represses the circadian oscillation of LHY2, indirectly activating PtoFT2 expression. Thus, PtoHY5a suppresses short day-induced growth cessation and bud set. Accordingly, PtoHY5a knockout facilitates dormancy induction. PtoHY5a also inhibits bud-break in poplar by controlling gibberellic acid (GA) levels in apical buds. Additionally, PtoHY5a regulates the photoperiodic control of seasonal growth downstream of phytochrome PHYB2. Thus, PtoHY5a modulates seasonal growth in poplar by regulating the PtoPHYB2–PtoHY5a–PtoFT2 module to determine the onset of winter dormancy, and by fine-tuning GA levels to control bud-break."
Authors: Yilong Yao, Denghao Xiang, Nai Wu, Yao Wang, Yu Chen, Yang Yuan, Ying Ye, Dan Hu, Chang Zheng, Yu Yan, Qingya Lv, Xiaokai Li, Guoxing Chen, Honghong Hu, Haiyan Xiong, Shaobing Peng and Lizhong Xiong.
Molecular Plant (2023)
Abstract: "Rice ratooning, the fast outgrowth of dormant buds on stubble, is an important cropping practice in rice production. However, the low ratooning ability (RA) of most rice varieties restricts the application of this cost-efficient system, and the genetic basis of RA remains unknown. In this study, we dissected the genetic architecture of RA by a genome-wide association study in a natural rice population. Rice ratooning ability 3 (RRA3), encoding a hitherto not characterized nucleoredoxin involved in reduction of disulfide bonds, was identified as the causal gene of a major locus controlling RA. Overexpression of RRA3 in rice significantly accelerated leaf senescence and reduced RA, whereas knockout of RRA3 significantly delayed leaf senescence and increased RA and ratoon yield. We demonstrated that RRA3 interacts with Oryza sativa histidine kinase 4 (OHK4), a cytokinin receptor, and inhibits the dimerization of OHK4 through disulfide bond reduction. This inhibition ultimately led to decreased cytokinin signaling and reduced RA. In addition, variations in the RRA3 promoter were identified to be associated with RA. Introgression of a superior haplotype with weak expression of RRA3 into the elite rice variety Guichao 2 significantly increased RA and ratoon yield by 23.8%. Collectively, this study not only uncovers an undocumented regulatory mechanism of cytokinin signaling through de-dimerization of a histidine kinase receptor—but also provides an eximious gene with promising value for ratoon rice breeding."
Authors: Fuli Ma, Shanqi Zhang, Yu Yao, Mengting Chen, Ning Zhang, Mingsheng Deng, Wei Chen, Chi Ma, Xinyue Zhang, Chenglong Guo, Xiang Huang, Zhenyuan Zhang, Yamei Li, Tingyi Li, Junyong Zhou, Qibao Sun and Jun Sun.
Horticulture Research (2023)
Abstract: "Jujube witches’ broom (JWB) phytoplasmas parasitize the sieve tubes of diseased phloem and cause an excessive proliferation of axillary shoots from dormant lateral buds to favour their transmission. In previous research, two JWB effectors, SJP1 and SJP2, were identified to induce lateral bud outgrowth by disrupting ZjBRC1-mediated auxin flux. However, the pathogenesis of JWB disease remains largely unknown. Here, tissue-specific transcriptional reprogramming was examined to gain insight into the genetic mechanisms acting inside jujube lateral buds under JWB phytoplasma infection. JWB phytoplasmas modulated a series of plant signalling networks involved in lateral bud development and defence, including auxin, abscisic acid (ABA), ethylene, jasmonic acid, and salicylic acid. JWB-induced bud outgrowth was accompanied by downregulation of ABA synthesis within lateral buds. ABA application rescued the bushy appearances of transgenic Arabidopsis overexpressing SJP1 and SJP2 in Col-0 and ZjBRC1 in the brc1-2 mutant. Furthermore, the expression of ZjBRC1 and ABA-related genes ZjHB40 and ZjNCED3 was negatively correlated with lateral main bud outgrowth in decapitated healthy jujube. Molecular evidence showed that ZjBRC1 interacted with ZjBRC2 via its N-terminus to activate ZjHB40 and ZjNCED3 expression and ABA accumulation in transgenic jujube calli. In addition, ZjBRC1 widely regulated differentially expressed genes related to ABA homeostasis and ABA signalling, especially by binding to and suppressing ABA receptors. Therefore, these results suggest that JWB phytoplasmas hijack the ZjBRC1-mediated ABA pathways to stimulate lateral bud outgrowth and expansion, providing a strategy to engineer plants resistant to JWB phytoplasma disease and regulate woody plant architecture to promote crop yield and quality."
Authors: Carlos Hernán Barrera-Rojas, Mateus Henrique Vicente, Diego Armando Pinheiro Brito, Eder M. Silva, Aitor Muñoz Lopez, Leticia F. Ferigolo, Rafael Monteiro do Carmo, Carolina M. S. Silva, Geraldo F. F. Silva, Joao P. O. Correa, Marcela M. Notini, Luciano Freschi, Pilar Cubas and Fabio T. S. Nogueira.
Journal of Experimental Botany (2023)
Abstract: "The miRNA156 (miR156)/SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL/SBP) regulatory hub is highly conserved among phylogenetically distinct species, but how it interconnects multiple pathways to converge to common integrators controlling shoot architecture is still unclear. Here, we demonstrated that the miR156/SlSBP15 node modulates tomato shoot branching by connecting multiple phytohormones with classical genetic pathways regulating both axillary bud development and outgrowth. miR156-overexpressing plants (156-OE) displayed high shoot branching, whereas plants overexpressing a miR156-resistant SlSBP15 allele (rSBP15) showed arrested shoot branching. Importantly, the rSBP15 allele was able to partially restore the wild-type shoot branching phenotype in the 156-OE background. rSBP15 plants have tiny axillary buds, and their activation is dependent on shoot apex-derived auxin transport inhibition. Hormonal measurements revealed that indole-3-acetic acid (IAA) and abscisic acid (ABA) concentrations were lower in 156-OE and higher in rSBP15 axillary buds, respectively. Genetic and molecular data indicated that SlSBP15 regulates axillary bud development and outgrowth by inhibiting auxin transport and GOBLET (GOB) activity, and by interacting with tomato BRANCHED1b (SlBRC1b) to control ABA levels within axillary buds. Collectively, our data provide a new mechanism by which the miR156/SPL/SBP hub regulates shoot branching, and suggest that modulating SlSBP15 activity might have potential applications in shaping tomato shoot architecture."
Authors: Ya-Lin Zhao, Yong Li, Ke Cao, Jia-Long Yao, Hang-Ling Bie, Irshad Ahmad Khan, Wei-Chao Fang, Chang-Wen Chen, Xin-Wei Wang, Jin-Long Wu, Wen-Wu Guo and Li-Rong Wang.
Plant Physiology (2023)
Abstract: "Bud dormancy is crucial for winter survival and is characterized by the inability of the bud meristem to respond to growth-promotive signals before the chilling requirement (CR) is met. However, our understanding of the genetic mechanism regulating CR and bud dormancy remains limited. This study identified PpDAM6 (DORMANCY-ASSOCIATED MADS-box) as a key gene for CR using a genome-wide association study analysis based on structural variations in 345 peach (Prunus persica (L.) Batsch) accessions. The function of PpDAM6 in CR regulation was demonstrated by transiently silencing the gene in peach buds and stably overexpressing the gene in transgenic apple (Malus × domestica) plants. The results showed an evolutionarily conserved function of PpDAM6 in regulating bud dormancy release, followed by vegetative growth and flowering, in peach and apple. The 30-bp deletion in the PpDAM6 promoter was substantially associated with reducing PpDAM6 expression in low-CR accessions. A PCR marker based on the 30-bp indel was developed to distinguish peach plants with non-low and low CR. Modification of the H3K27me3 marker at the PpDAM6 locus showed no apparent change across the dormancy process in low- and non-low- CR cultivars. Additionally, H3K27me3 modification occurred earlier in low-CR cultivars on a genome-wide scale. PpDAM6 could mediate cell–cell communication by inducing the expression of the downstream genes PpNCED1 (9-cis-epoxycarotenoid dioxygenase 1), encoding a key enzyme for ABA biosynthesis, and CALS (CALLOSE SYNTHASE), encoding callose synthase. We shed light on a gene regulatory network formed by PpDAM6-containing complexes that mediate CR underlying dormancy and bud break in peach. A better understanding of the genetic basis for natural variations of CR can help breeders develop cultivars with different CR for growing in different geographical regions."
Authors: Shangyu Chen, Xuewei Song, Qixiang Zheng, Yuqi Liu, Jingquan Yu, Yanhong Zhou and Xiaojian Xia.
Journal of Experimental Botany (2023)
Abstract: "Plant architecture imposes a large impact on crop yield. IDEAL PLANT ARCHITECTURE 1 (IPA1), which encodes a SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factor, is a target of molecular design for improving grain yield. However, the roles of SPL transcription factors in regulating tomato (Solanum lycopersicum) plant architecture are unclear. Here, we show that the expression of SPL13 is downregulated in the lateral buds of strigolactones (SLs)-deficient ccd mutants and is induced by GR24 (a synthetic analogue of SL). Knockout of SPL13 by CRISPR/Cas9 resulted in higher levels of cytokinins (CKs) and transcripts of CK synthesis gene ISOPENTENYL TRANSFERASES 1 (IPT1) in the stem nodes and more growth of lateral buds. GR24 suppresses CKs synthesis and lateral bud growth in ccd mutants but is not effective in spl13 mutants. Meanwhile, silencing of IPT1 gene inhibited bud growth of spl13 mutants. Interestingly, SLs levels in root extracts and exudates are significantly increased in spl13 mutants. Molecular studies indicated that SPL13 directly represses the transcription of IPT1 and the SL synthesis genes CAROTENOID CLEAVAGE DIOXYGENASE 7 (CCD7) and MORE AXILLARY GROWTH 1 (MAX1). The results demonstrate that SPL13 acts downstream of SL to suppress lateral bud growth by inhibiting CKs synthesis in tomato. Tuning the expression of SPL13 is a potential approach for decreasing the number of lateral shoots in tomato."
Authors: WEN Yun-ze, HE Peng, BAI Xiao-han, ZHANG Hui-zhi, ZHANG Yun-feng and YU Jia-ning.
Journal of Integrative Agriculture (2023)
Abstract: "Cotton is one of the most important economic crops in the world and is a major source of fiber in the textile industry. Strigolactones (SLs) are a class of carotenoid-derived plant hormones involved in many processes of plant growth and development; however, SL functions in fiber development remain largely unknown. Here, we found that the endogenous SLs were significantly higher in fibers 20 days post-anthesis (DPA). Exogenous SLs significantly increased fiber length and cell wall thickness. Furthermore, we cloned three key SLs biosynthetic genes, namely GhD27, GhMAX3, and GhMAX4, which were highly expressed in fibers, and subcellular localization analyses revealed that GhD27, GhMAX3, and GhMAX4 were localized in the chloroplast. The exogenous expression of GhD27, GhMAX3, and GhMAX4 complemented the physiological phenotypes of d27, max3, and max4 mutations in Arabidopsis, respectively. Knockdown of GhD27, GhMAX3, and GhMAX4 in cotton resulted in an increased number of axillary buds and leaves, decreased fiber length, and significantly reduced fiber thickness. These findings revealed that SLs participate in plant growth, fiber elongation, and secondary cell wall formation in cotton. These results provide new and effective genetic resources for improving cotton fiber yield and plant architecture."
Authors: Raz Danieli, Shmuel Assouline, Bolaji Babajide Salam, Ondřej Vrobel, Paula Teper-Bamnolker, Eduard Belausov, David Granot, Petr Tarkowski and Dani Eshel.
Plant, Cell & Environment (2023)
Abstract: "Endodormancy (ED) is a crucial stage in the life cycle of many perennial plants. ED release requires accumulating a certain amount of cold exposure, measured as chilling units. However, the mechanism governing the effect of chilling on ED duration is poorly understood. We used the potato tuber model to investigate the response to chilling as associated with ED release. We measured the accumulation of specific sugars during and after chilling, defined as sugar units. We discovered that ED duration correlated better with sugar units accumulation than chilling units. A logistic function was developed based on sugar units measurements to predict ED duration. Knockout or overexpression of the vacuolar invertase gene (StVInv) unexpectedly modified sugar units levels and extended or shortened ED, respectively. Silencing the energy sensor SNF1-related protein kinase 1, induced higher sugar units accumulation and shorter ED. Sugar units accumulation induced by chilling or transgenic lines reduced plasmodesmal (PD) closure in the dormant bud meristem. Chilling or knockout of abscisic acid (ABA) 8′-hydroxylase induced ABA accumulation, in parallel to sweetening, and antagonistically promoted PD closure. Our results suggest that chilling induce sugar units and ABA accumulation, resulting in antagonistic signals for symplastic connection of the dormant bud."
Authors: Christine A Beveridge, Catherine Rameau, Akila Wijerathna-Yapa.
Jornal of Experimental Botany (2023)
Abstract: "The process of apical dominance by which the apical bud/shoot tip of the plant inhibits the outgrowth of axillary buds located below has been studied for more than a century. Different approaches were used over time with first the physiology era, the genetic era, and then the multidisciplinary era. During the physiology era, auxin was thought of as the master regulator of apical dominance acting indirectly to inhibit bud outgrowth via unknown secondary messenger(s). Potential candidates were cytokinin (CK) and abscisic acid (ABA). The genetic era with the screening of shoot branching mutants in different species revealed the existence of a novel carotenoid-derived branching inhibitor and led to the significant discovery of strigolactones (SLs) as a novel class of plant hormones. The re-discovery of the major role of sugars in apical dominance emerged from modern physiology experiments and involves ongoing work with genetic material affected in sugar-signalling. As crops and natural selection rely on the emergent properties of networks such as this branching network, future work should explore the whole network, the details of which are critical but not individually sufficient to solve the wicked problems of sustainable food supply and climate change."
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Authors: Jihua Ding, Kejing Wang, Shashank Pandey, Mariano Perales, Isabel Allona, Md Rezaul Islam Khan, Victor B. Busov, Rishikesh P. Bhalerao
Journal of Experimental Botany (2024)
Abstract: "Seasonal bud dormancy in perennial woody plants is a crucial and intricate process that is vital for the survival and development of plants. Over the past few decades, significant advancements have been made in understanding many features of bud dormancy, particularly in model species, where certain molecular mechanisms underlying this process have been elucidated. In this review, we provide an overview of recent molecular progress in understanding bud dormancy in trees, with a specific emphasis on the integration of common signaling and molecular mechanisms identified across different tree species. Additionally, we address some challenges that have emerged in the in-depth understanding of bud dormancy and offer insights for future studies."
Authors: Jiacai Chen, Liu Liu, Guanghui Wang, Guangxin Chen, Xiaofeng Liu, Min Li, Lijie Han, Weiyuan Song, Shaoyun Wang, Chuang Li, Zhongyi Wang, Yuxiang Huang, Chaoheng Gu, Zhengan Yang, Zhaoyang Zhou, Jianyu Zhao and Xiaolan Zhang.
The Plant Cell (2024)
One-sentence summary: CsAGL16 positively regulates axillary bud outgrowth in cucumber by directly promoting CsCYP707A4-mediated ABA catabolism, and CsGRF1 interacts with CsAGL16 and antagonizes the CsAGL16-mediated CsCYP707A4 activation.
Abstract: "Lateral branches are important components of shoot architecture and directly affect crop yield and production cost. Although sporadic studies have implicated abscisic acid (ABA) biosynthesis in axillary bud outgrowth, the function of ABA catabolism and its upstream regulators in shoot branching remain elusive. Here, we showed that the MADS-box transcription factor AGAMOUS-LIKE 16 (CsAGL16) is a positive regulator of axillary bud outgrowth in cucumber (Cucumis sativus). Functional disruption of CsAGL16 led to reduced bud outgrowth, whereas overexpression of CsAGL16 resulted in enhanced branching. CsAGL16 directly binds to the promoter of the ABA 8'-hydroxylase gene CsCYP707A4 and promotes its expression. Loss of CsCYP707A4 function inhibited axillary bud outgrowth and increased ABA levels. Elevated expression of CsCYP707A4 or treatment with an ABA biosynthesis inhibitor largely rescued the Csagl16 mutant phenotype. Moreover, cucumber General Regulatory Factor 1 (CsGRF1) interacts with CsAGL16 and antagonizes CsAGL16-mediated CsCYP707A4 activation. Disruption of CsGRF1 resulted in elongated branches and decreased ABA levels in the axillary buds. The Csagl16 Csgrf1 double mutant exhibited a branching phenotype resembling that of the Csagl16 single mutant. Therefore, our data suggest that the CsAGL16–CsGRF1 module regulates axillary bud outgrowth via CsCYP707A4-mediated ABA catabolism in cucumber. Our findings provide a strategy to manipulate ABA levels in axillary buds during crop breeding to produce desirable branching phenotypes."
Authors: Wenzhen Ku, Yi Su, Xiaoyun Peng, Ruozhong Wang, Haiou Li and Langtao Xiao.
Plants (2024)
Abstract: "Axillary bud outgrowth, a key factor in ratoon rice yield formation, is regulated by several phytohormone signals. The regulatory mechanism of key genes underlying ratoon buds in response to phytohormones in ratoon rice has been less reported. In this study, GR24 (a strigolactone analogue) was used to analyze the ratooning characteristics in rice cultivar Huanghuazhan (HHZ). Results show that the elongation of the axillary buds in the first seasonal rice was significantly inhibited and the ratoon rate was reduced at most by up to 40% with GR24 treatment. Compared with the control, a significant reduction in the content of auxin and cytokinin in the second bud from the upper spike could be detected after GR24 treatment, especially 3 days after treatment. Transcriptome analysis suggested that there were at least 742 and 2877 differentially expressed genes (DEGs) within 6 h of GR24 treatment and 12 h of GR24 treatment, respectively. Further bioinformatics analysis revealed that GR24 treatment had a significant effect on the homeostasis and signal transduction of cytokinin and auxin. It is noteworthy that the gene expression levels of OsCKX1, OsCKX2, OsGH3.6, and OsGH3.8, which are involved in cytokinin or auxin metabolism, were enhanced by the 12 h GR24 treatment. Taken overall, this study showed the gene regulatory network of auxin and cytokinin homeostasis to be regulated by strigolactone in the axillary bud outgrowth of ratoon rice, which highlights the importance of these biological pathways in the regulation of axillary bud outgrowth in ratoon rice and would provide theoretical support for the molecular breeding of ratoon rice."
Authors: Nora Flynn.
The Plant Cell (2024)
Excerpts: "Yongfeng Gao and colleagues (Gao et al. 2024) expose a new regulatory model for short-day-induced dormancy that involves a poplar (Populus tomentosa) ortholog of the Arabidopsis photomorphogenesis regulatory factor ELONGATED HYPOCOTYL 5 (HY5), HY5a. The model introduces poplar HY5a as a coordinator of growth cessation and bud set that promotes FLOWERING LOCUS T2 (FT2) transcription through both direct and indirect routes (Figure)."
"Finally, the phenotypes of HY5a-OE and HY5a-KO plants indicated that HY5a may also be involved in bud burst. To further investigate this hypothesis, the authors compared the transcript abundances of genes related to the synthesis and breakdown of gibberellins (GA), plant hormones involved in dormancy release (Rinne et al., 2011). The activity of GA synthesis genes increased without HY5a, along with the levels of active GA. Therefore, HY5a is not only a novel regulator of short-day-induced dormancy in poplar, but also a broader controller of seasonal growth that negatively regulates GA in buds. Figure."
Authors: Penelope Lindsay, Kyle W. Swentowsky and David Jackson.
Molecular Plant (2024)
Abstract: "Meristems are stem cell-containing structures that produce all plant organs and are therefore important targets for crop improvement. Developmental regulators control the balance and rate of cell divisions within the meristem. Altering these regulators impacts meristem architecture and as a consequence, plant form. In this review, we discuss genes involved in regulating the shoot apical meristem (SAM), inflorescence meristem (IM), axillary meristem (AM), root apical meristem (RAM), and vascular cambium in plants. We also highlight examples of how crop breeders have manipulated developmental regulators to modify meristem growth, altering crop traits including inflorescence size and branching patterns. Plant transformation techniques are another innovation related to plant meristem research, since they make crop genome engineering possible. We discuss recent advances in plant transformation research made possible by studying genes that control meristem development. Finally, we conclude with a discussion of how meristem research can contribute to crop improvement in the coming decades."
Authors: Yundong Yuan, Said Khourchi, Shujia Li, Yanfang Du, and Pierre Delaplace.
Plants (2023)
Abstract: "Shoot branching is a complex and tightly regulated developmental process that is essential for determining plant architecture and crop yields. The outgrowth of tiller buds is a crucial step in shoot branching, and it is influenced by a variety of internal and external cues. This review provides an extensive overview of the genetic, plant hormonal, and environmental factors that regulate shoot branching in several plant species, including rice, Arabidopsis, tomato, and wheat. We especially highlight the central role of TEOSINTE BRANCHED 1 (TB1), a key gene in orchestrating bud outgrowth. In addition, we discuss how the phytohormones cytokinins, strigolactones, and auxin interact to regulate tillering/branching. We also shed light on the involvement of sugar, an integral component of plant development, which can impact bud outgrowth in both trophic and signaling ways. Finally, we emphasize the substantial influence of environmental factors, such as light, temperature, water availability, biotic stresses, and nutrients, on shoot branching. In summary, this review offers a comprehensive evaluation of the multifaced regulatory mechanisms that underpin shoot branching and highlights the adaptable nature of plants to survive and persist in fluctuating environmental conditions."
Authors: Rameshwar Sharma and Yellamaraju Sreelakshmi.
Journal of Experimental Botany (2023)
Abstract: "Axillary buds (ABs) are dormant buds located in the leaf axils of plants, which have the potential to develop into branches or flowers under appropriate conditions. At the molecular-genetic level, the miR156/SPL/SPB module regulates the development of ABs in plants, thus influencing plant architecture. Auxins are plant hormones that regulate various aspects of plant growth and development, including AB activity. Barrera-Rojas et al. (2023) show that suppressing AB outgrowth elevates auxin levels and lowers GOBLET expression, probably by suppressing its transcription by SBP15. Their findings provide insights into the regulation of AB outgrowth and tomato shoot architecture."
Authors: Bin Ma, Jianbo Zhu and Xianzhong Huang.
BMC Plant Biology (2023)
Abstract: "Background - Strigolactones (SLs) are a recently discovered class of plant hormones. SUPPRESSOR OF MAX2 1 (SMAX1)-like proteins, key component of the SL signaling pathway, have been studied extensively for their roles in regulating plant growth and development, such as plant branching. However, systematic identification and functional characterization of SMXL genes in cotton (Gossypium sp.), an important fiber and oil crop, has rarely been conducted. Results - We identified 210 SMXL genes from 21 plant genomes and examined their evolutionary relationships. The structural characteristics of the SMXL genes and their encoded proteins exhibited both consistency and diversity. All plant SMXL proteins possess a conserved Clp-N domain, P-loop NTPase, and EAR motif. We identified 63 SMXL genes in cotton and classified these into four evolutionary branches. Gene expression analysis revealed tissue-specific expression patterns of GhSMXL genes, with some upregulated in response to GR24 treatment. Protein co-expression network analysis showed that GhSMXL6, GhSMXL7-1, and GhSMXL7-2 mainly interact with proteins functioning in growth and development, while virus-induced gene silencing revealed that GhSMAX1-1 and GhSMAX1-2 suppress the growth and development of axillary buds. Conclusions - SMXL gene family members show evolutionary diversification through the green plant lineage. GhSMXL6/7–1/7–2 genes play critical roles in the SL signaling pathway, while GhSMXL1-1 and GhSMXL1-2 function redundantly in growth of axillary buds. Characterization of the cotton SMXL gene family provides new insights into their roles in responding to SL signals and in plant growth and development. Genes identified in this study could be used as the candidate genes for improvement of plant architecture and crop yield."
Authors: Elizabeth A. Dun, Philip B. Brewer, Elizabeth M. J. Gillam and Christine A. Beveridge.
Plant and Cell Physiology (2023)
Abstract: There have been substantial advances in our understanding of many aspects of strigolactone regulation of branching since the discovery of strigolactones as phytohormones (Gomez-Roldan et al., 2008; Umehara et al., 2008). These include further insights into the network of phytohormones and other signals that regulate branching, as well as deep insights into strigolactone biosynthesis, metabolism, transport, perception, and downstream signalling. In this review, we provide an update on recent advances in our understanding of how the strigolactone pathway co-ordinately and dynamically regulates bud outgrowth and pose some important outstanding questions that are yet to be resolved
Authors: Kyoichi Kodama, Xiaonan Xie, Junko Kyozuka.
Plant and Cell Physiology (2023)
Abstract: "Strigolactones (SLs), lactone-containing carotenoid derivatives, function as signaling molecules in the rhizosphere, inducing symbiosis with arbuscular mycorrhizal. In addition, as a class of plant hormones, SLs control plant growth and development in flowering plants (angiosperms). Recent studies show that the ancestral function of SLs, which precede terrestrialization of plants, is as rhizosphere signaling molecules. SLs were then recruited as a class of plant hormones through the step-by-step acquisition of signaling components. The D14 gene encoding the SL receptor arose by gene duplication of KARRIKIN INSENSITIVE2 (KAI2), the receptor of karrikins and KAI2 ligand (KL), an unknown ligand, in the common ancestor of seed plants. KL signaling targets SMAX1, a repressor protein. On the other hand, the SL signaling targets SMXL78 subclade repressors, which arose by duplication of SMAX1 in angiosperms. Thus, gymnosperms contain the SL receptor D14 but not SMXL78, the SL signaling–specific repressor proteins. We studied two gymnosperm species, ginkgo (Ginkgo biloba) and Japanese umbrella pine (Sciadopitys verticillata), to clarify whether SLs are perceived and the signals are transduced in gymnosperms. We show that D14 and KAI2 of ginkgo and Japanese umbrella pine specifically perceive an SL analog and KL mimic, respectively. Furthermore, our results suggest that both SL signaling and KL signaling target SMAX1, and the specific localization of the receptor may result in the specificity of the signaling in gymnosperms."
Authors: Qian Zhao, Hao Chen, Dong Zhang and Juanjuan Ma.
Scientia Horticulturae (2023)
Highlights • MdRR9 has an ORF of 648 bp, which showed the highest expression level in the stem and was up-regulated earlier in response to 6-BA than decapitation treatment. • The subcellular localization of MdRR9 was in the nucleus. Ectopic expression of MdRR9 in tomato indicated that MdRR9 plays a positive role in branch control. • Yeast double-hybrid assay showed that MdRR9 may interact with MADS-box transcription factor 22-like (AGL9).
Abstract: "Response regulator 9 (RR9) is a typical member of type-A RRs whose transcription is rapidly increased by exogenous cytokinin (CTK). CTK stimulates the outgrowth of axillary buds in apples (Malus domestica). Previous studies showed that the decreased bud outgrowth activity of type-A rr mutants is paradoxical given that type-A RRs act as negative feedback regulators of CTK signaling in Arabidopsis. However, no systematic study of RR9 has been performed in apples. In this study, the genomic sequences of MdRR9, located on chromosome 14, were obtained. Sequencing identified MdRR9 as having an open reading frame (ORF) of 648 bp. Expression pattern showed MdRR9 has the highest expression level in the stem. MdRR9 was up-regulated earlier in response to 6-benzylaminopurine (6-BA, a synthetic type of CTK) than decapitation treatment. The subcellular localization of MdRR9 was in the nucleus. Ectopic expression of MdRR9 in tomatoes indicates that MdRR9 plays a positive role in branch control. A yeast double-hybrid assay showed that MdRR9 may interact with MADS-box transcription factor 22-like (MdAGL9), which gives us a new perspective to study the regulation of the bud outgrowth mechanism of RR9 in the future."
Abstract: Yang Dong, Jing Liu, Liyuan Huang, Lina Yang, Muhammad Khalil-Ur-Rehman, Huan Zheng and Jianmin Tao.
Environmental and Experimental Botany (2023)
Highlights • VvSVP3 induces callose synthesis and VvPYL9 expression, and simultaneously negatively regulates the GA metabolic pathway to maintain dormancy.
Abstract: "Bud dormancy is an essential and complex physiological process in perennial plants. Abscisic acid (ABA) is the major hormone regulating bud dormancy, however, the gene, SHORT VEGETATIVE PHASE (SVP) also plays a pivotal role. The combined regulation of SVP and ABA in the endodormancy network remains poorly characterized. In the present study, we demonstrate the growth inhibitory functions of VvSVP3 by its overexpressing it in tobacco and poplar. VvSVP3-overexpressing poplar plants prematurely stopped growing under short day, exhibiting delayed bud break in early spring. VvSVP3 regulates ABA, the gibberellic acid (GA) pathway, and the callose synthesis to promote dormancy within its network. In addition, exogenous application of ABA positively affects VvSVP3 expression. A transcriptomics and proteomics combined approach identified that VvPYL9 is a target gene of VvSVP3, which directly binds to a CArG motif in the VvPYL9 promoter to activate its expression. In summary, our results revealed the feedback regulation between VvSVP3 gene, ABA metabolism, and the dormancy signaling pathway in grape. It also provides new insights into the functional role of callose and ABA regulation in dormancy."
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