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Authors: Chengjuan Cao, Shuaiqiang Guo, Ping Deng, Shiyi Yang, Jing Xu, Tengfei Hu, Zhijuan Hu, Di Chen, Hongsheng Zhang, Ian Paul Navea, Joong Hyoun Chin, Wenhua Zhang and Wen Jing.
The Plant Journal (2024)
Significance Statement: "GA 2-oxidases (GA2oxs) play crucial roles in regulating plant architecture and yield by inactivating endogenous bioactive GAs and their precursors, but the regulatory mechanisms of GA2ox gene expression remain unclear. This study identifies that OsBLH4, a member of the BEL1-like homeodomain proteins, acts upstream of OsGA2ox1, modulates endogenous bioactive GA levels, and regulates stem elongation and reproductive development in rice."
Abstract: "Gibberellins (GAs) play crucial roles in regulating plant architecture and grain yield of crops. In rice, the inactivation of endogenous bioactive GAs and their precursors by GA 2-oxidases (GA2oxs) regulates stem elongation and reproductive development. However, the regulatory mechanisms of GA2ox gene expression, especially in rice reproductive organs, are unknown. The BEL1-like homeodomain protein OsBLH4, a negative regulatory factor for the rice OsGA2ox1 gene, was identified in this study. Loss of OsBLH4 function results in decreased bioactive GA levels and pleiotropic phenotypes, including reduced plant height, decreased grain number per panicle, and delayed heading date, as also observed in OsGA2ox1-overexpressing plants. Consistent with the mutant phenotype, OsBLH4 was predominantly expressed in shoots and young spikelets; its encoded protein was exclusively localized in the nucleus. Molecular analysis demonstrated that OsBLH4 directly bound to the promoter region of OsGA2ox1 to repress its expression. Genetic assays revealed that OsBLH4 acts upstream of OsGA2ox1 to control rice plant height, grain number, and heading date. Taken together, these results indicate a crucial role for OsBLH4 in regulating rice plant architecture and yield potential via regulation of bioactive GA levels, and provide a potential strategy for genetic improvements of rice."
Authors: Rui Yan, Tianle Zhang, Yuan Wang, Wenxiu Wang, Rahat Sharif, Jiale Liu, Qinglong Dong, Haoan Luan, Xuemei Zhang, Han Li, Suping Guo, Guohui Qi and Peng Jia.
Plant Physiology and Biochemistry (2024)
Highlights: • Seventeen GA2-oxidase genes identified in apple clustered into four clades. • MdGA2ox7 responded to cold and salt treatments. • MdGA2ox7 was activated during light-induced anthocyanin accumulation. • MdGA2ox7 alleviated cold and salt stress damage. • MdGA2ox7 promoted anthocyanin biosynthesis.
Abstract: "Apple (Malus domestica Borkh.) is a widely cultivated fruit crop worldwide but often suffers from abiotic stresses such as salt and cold. Gibberellic acid (GA) plays a pivotal in controlling plant development, environmental adaptability, and secondary metabolism. The GA2-oxidase (GA2ox) is responsible for the deactivation of bioactive GA. In this study, seventeen GA2-oxidase genes were identified in the apple genome, and these members could be clustered into four clades based on phylogenetic relationships and conserved domain structures. MdGA2ox7 exhibited robust expression across various tissues, responded to cold and salt treatments, and was triggered in apple fruit peels via light-induced anthocyanin accumulation. Subcellular localization prediction and experiments confirmed that MdGA2ox7 was located in the cytoplasm. Overexpression of MdGA2ox7 in Arabidopsis caused a lower level of active GA and led to GA-deficient phenotypes, such as dwarfism and delayed flowering. MdGA2ox7 alleviated cold and salt stress damage in both Arabidopsis and apple in concert with melatonin (MT). Additionally, MdGA2ox7 enhanced anthocyanin biosynthesis in apple calli and activated genes involved in anthocyanin synthesis. These findings provide new insights into the functions of apple GA2ox in regulating development, stress tolerance, and secondary metabolism."
Authors: Ting Li, Yongqin Wang, Annelore Natran, Yi Zhang, Hao Wang, Kangxi Du, Peng Qin, Hua Yuan, Weilan Chen, Bin Tu, Dirk Inzé and Marieke Dubois.
New Phytologist (2024)
Abstract: "Gibberellic acid (GA) plays a central role in many plant developmental processes and is crucial for crop improvement. DELLA proteins, the core suppressors in the GA signaling pathway, are degraded by GA via the 26S proteasomal pathway to release the GA response. However, little is known about the phosphorylation-mediated regulation of DELLA proteins. In this study, we combined GA response assays with protein–protein interaction analysis to infer the connection between Arabidopsis thaliana DELLAs and the C-TERMINAL DOMAIN PHOSPHATASE-LIKE 3 (CPL3), a phosphatase involved in the dephosphorylation of RNA polymerase II. We show that CPL3 directly interacts with DELLA proteins and promotes DELLA protein stability by inhibiting its degradation by the 26S proteasome. Consequently, CPL3 negatively modulates multiple GA-mediated processes of plant development, including hypocotyl elongation, flowering time, and anthocyanin accumulation. Taken together, our findings demonstrate that CPL3 serves as a novel regulator that could improve DELLA stability and thereby participate in GA signaling transduction."
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: Yongyu Huang, Andreas Maurer, Ricardo F. H. Giehl, Shuangshuang Zhao, Guy Golan, Venkatasubbu Thirulogachandar, Guoliang Li, Yusheng Zhao, Corinna Trautewig, Axel Himmelbach, Andreas Börner, Murukarthick Jayakodi, Nils Stein, Martin Mascher, Klaus Pillen and Thorsten Schnurbusch.
Molecular Biology and Evolution (2024)
Abstract: "Vascular plants have segmented body axes with iterative nodes and internodes. Appropriate node initiation and internode elongation are fundamental to plant fitness and crop yield; however, how these events are spatiotemporally coordinated remains elusive. We show that in barley (Hordeum vulgare L.), selections during domestication have extended the apical meristematic phase to promote node initiation, but constrained subsequent internode elongation. In both vegetative and reproductive phases, internode elongation displays a dynamic proximal – distal gradient, and among subpopulations of domesticated barleys worldwide, node initiation and proximal internode elongation are associated with latitudinal and longitudinal gradients, respectively. Genetic and functional analyses suggest that, in addition to their converging roles in node initiation, flowering-time genes have been repurposed to specify the timing and duration of internode elongation. Our study provides an integrated view of barley node initiation and internode elongation, and suggests that plant architecture should be recognized as a collection of dynamic phytomeric units in the context of crop adaptive evolution."
Authors: Jingye Cheng, Yong Jia, Camilla Hill, Tianhua He, Ke Wang, Ganggang Guo, Sergey Shabala, Meixue Zhou, Yong Han and Chengdao Li.
Journal of Advanced Research (2024)
Highlights • Genes concoding gibberellin 2-oxidase are expanded to ten copies in the barley genome and shown copy number variation in the barley pan genome. • The ten genes are transcriptionally expressed in a tissue-specific way, indicating divergent biological functions. • Functions of two genes of gibberellin 2-oxidase were validated by virus-induced gene silencing and CRISPR gene editing to control different agronomic traits. • A natural mutant for the gene was identified with semidwarf stature, early flowering and heavier seeds. • The results provide a promising strategy to minimise the adverse effects of the original Green Revolution semi-dwarf genes to develop the next generation of barley cultivars better adapted to a changing climate.
Abstract: "Introduction - Gibberellin (GA) is a vital phytohormone in regulating plant growth and development. During the “Green Revolution”, modification of GA-related genes created semi-dwarfing phenotype in cereal crops but adversely affected grain weight. Gibberellin 2-oxidases (GA2oxs) in barley act as key catabolic enzymes in deactivating GA, but their functions are still less known. Objectives - This study investigates the physiological function of two HvGA2ox genes in barley and identifies novel semi-dwarf alleles with minimum impacts on other agronomic traits. Methods - Virus-induced gene silencing and CRISPR/Cas9 technology were used to manipulate gene expression of HvGA2ox9 and HvGA2ox8a in barley and RNA-seq was conducted to compare the transcriptome between wild type and mutants. Also, field trials in multiple environments were performed to detect the functional haplotypes. Results - There were ten GA2oxs that distinctly expressed in shoot, tiller, inflorescence, grain, embryo and root. Knockdown of HvGA2ox9 did not affect plant height, while ga2ox8a mutants generated by CRISPR/Cas9 increased plant height and significantly altered seed width and weight due to the increased bioactive GA4 level. RNA-seq analysis revealed that genes involved in starch and sucrose metabolism were significantly decreased in the inflorescence of ga2ox8a mutants. Furthermore, haplotype analysis revealed one naturally occurring HvGA2ox8a haplotype was associated with decreased plant height, early flowering and wider and heavier seed. Conclusion - Our results demonstrate the potential of manipulating GA2ox genes to fine tune GA signalling and biofunctions in desired plant tissues and open a promising avenue for minimising the trade-off effects of Green Revolution semi-dwarfing genes on grain size and weight. The knowledge will promote the development of next generation barley cultivars with better adaptation to a changing climate."
Author: Guadalupe L. Fernández-Milmanda
Plant Physiology (2023)
Excerpts: "In this issue of Plant Physiology, Wang et al., 2023 found two molecular pathways that regulate GA metabolism in response to touch, one dependent on JA and one dependent on an unexpected hormonal player, ethylene (ET)."
"Thus, the authors characterized touch-induced morphogenesis in two ET-insensitive lines, ein2 and ein3 eil1. As expected, repetitive touch repressed growth of wild-type plants, leading to more compact (reduced diameter) rosettes that also flowered later than their unstimulated counter parts. The ein2 and ein3 eil1 plants were also responsive to touch but, interestingly, the effect of treatment was stronger than in the wild type, suggesting that ET could be a negative regulator of thigmomorphogenesis (Fig. 1, left)."
"As breakdown of GA is necessary for expression of thigmomorphogenesis (Lange & Lange, 2015), the authors measured levels of GA4, a bioactive GA, in the ET-insensitive lines. They found that touch treatment severely lowered the concentration of GA4 in the ein2 and ein3 eil1 plants, even to a greater extent than in the wild type......Consistent with this model, supplementation of touch-induced ein2 and ein3 eil1 plants with exogenous GA4 rescued the compact growth and delay in flowering time phenotypes."
"In conclusion, Wang and collaborators explored the connection between the pathways of two known regulators of touch-induced morphogenesis, JA and GA. They found that JA activates GA breakdown, leading to decreased growth and delayed flowering. The authors also incorporated ET to the picture. ET acts as negative regulator of thigmomorphogenesis, also through an effect on GA catabolism, but in this case ET represses GA catabolism, likely to prevent exaggerated responses. (Fig. 1). These findings position GA metabolism as a central node in thigmomorphogenesis."
Authors: Xin Zhao, Wenwen Liu, Palinuer Aiwaili, Han Zhang, Yanjie Xu, Zhaoyu Gu, Junping Gao and Bo Hong.
Plant Physiology (2023)
One-sentence summary: Short days accelerate the juvenile-to-adult transition by increasing endogenous gibberellin biosynthesis and perception in chrysanthemum, leading to entry into floral transformation.
Abstract: "The gibberellins (GAs) receptor GA INSENSITIVE DWARF1 (GID1) plays a central role in GA signal perception and transduction. The typical photoperiodic plant chrysanthemum (Chrysanthemum morifolium) only flowers when grown in short-day photoperiods. In addition, chrysanthemum flowering is also controlled by the aging pathway, but whether and how GAs participate in photoperiod- and age-dependent regulation of flowering remain unknown. Here, we demonstrate that photoperiod affects CmGID1B expression in response to GAs and developmental age. Moreover, we identified PHOTOLYASE/BLUE LIGHT RECEPTOR2, an atypical photocleavage synthase, as a CRYPTOCHROME-INTERACTING bHLH1 interactor with which it forms a complex in response to short days to activate CmGID1B transcription. Knocking down CmGID1B raised endogenous bioactive GA contents and GA signal perception, in turn modulating the expression of the aging-related genes MicroRNA156 and SQUAMOSA PROMOTER BINDING PROTEIN-LIKE3. We propose that exposure to short days accelerates the juvenile-to-adult transition by increasing endogenous GA contents and response to GAs, leading to entry into floral transformation."
Authors: Xunju Liu, Jiyuan Wang, Wanxia Sun, Irfan Ali Sabir, Li Wang, Zhengxin Lv, Zifan Tang, Haobo Liu, Ruie Liu, Songtao Jiu, Bénédicte Wenden and Caixi Zhang.
Scientia Horticulturae (2023)
Highlights • A significant decrease in the expression level of PavGA20ox-2 was observed after the GA4+7 treatment. • Upon overexpression of PavGA20ox-2, Arabidopsis thaliana plants grew taller, more flowers bloomed, and seeds germinated faster. • PavWRKY31 and pavhy5-like could induce and reduce the transcriptional expression of PavGA20ox-2, respectively.
Abstract: "GA20 oxidase (GA20ox) is an enzyme that regulates GA (Gibberellic acid) biosynthesis and is essential in maintaining the dynamic balance of gibberellin in plants. We identified the PavGA20ox-2 gene from sweet cherry. The expression level of PavGA20ox-2 increased from winter to spring and significantly decreased after GA4+7 treatment. Surprisingly, the expression level of PavGA20ox-2 in sweet cherry flower buds with transient infection of overexpression PavWRKY31 was significantly higher than that in the control group. Besides, PavWRKY31 is directly bound to the W-box motif in the promoter of PavGA20ox-2 to activate the transcriptional level of PavGA20ox-2. The plant height was also increased, and the flowering time was advanced when PavGA20ox-2 was overexpressed in Arabidopsis. Moreover, the seed germination rate of Arabidopsis thaliana was higher than that of the wild type. In conclusion, PavGA20ox-2 could promote plant growth, accelerate flowering time, and increase seed germination. Thus, PavGA20ox-2 is considered involved in regulating multiple processes of plant growth and development by affecting GA biosynthesis. Our results will contribute to a better understanding of the molecular mechanism of GA20ox-mediated fruit tree development."
Authors: Ying Wang, Jian’an Li, Purui Guo, Qian Liu, Shuangshuang Ren, Lemei Juan, Jiacheng He, Xiaofeng Tan and Jindong Yan.
Planta (2023)
Main conclusion Ectopic expression of Camellia oleifera Abel. gibberellin 20-oxidase 1 caused a taller phenotype, promoted secondary cell wall deposition, leaf enlargement, and early flowering, and reduced chlorophyll and anthocyanin accumulation and seed enlargement phenotype in Arabidopsis.
Abstract: "Plant height and secondary cell wall (SCW) deposition are important plant traits. Gibberellins (GAs) play important roles in regulating plant height and SCWs deposition. Gibberellin 20-oxidase (GA20ox) is an important enzyme involved in GA biosynthesis. In the present study, we identified a GA synthesis gene in Camellia oleifera. The total length of the CoGA20ox1 gene sequence was 1146 bp, encoding 381 amino acids. Transgenic plants with CoGA20ox1 had a taller phenotype; a seed enlargement phenotype; promoted SCWs deposition, leaf enlargement, and early flowering; and reduced chlorophyll and anthocyanin accumulation. Genetic analysis showed that the mutant ga20ox1-3 Arabidopsis partially rescued the phenotype of CoGA20ox1 overexpression plants. The results showed that CoGA20ox1 participates in the growth and development of C. oleifera. The morphological changes in CoGA20ox1 overexpressed plants provide a theoretical basis for further exploration of GA biosynthesis and analysis of the molecular mechanism in C. oleifera."
Authors: Yudan Wang, Shiwei Song, Yanwei Hao, Changming Chen, Xi Ou, Bin He, Jiewen Zhang, Zhehao Jiang, Chengming Li, Shuaiwei Zhang, Wei Su and Riyuan Chen.
Horticultural Research (2023)
Abstract: "Gibberellin (GA) plays a major role in controlling Brassica rapa stalk development. As an essential negative regulator of GA signal transduction, DELLA proteins may exert significant effects on stalk development. However, the regulatory mechanisms underlying this regulation remain unclear. In this study, we report highly efficient and inheritable mutagenesis using the CRISPR/Cas9 gene editing system in BraPDS (phytoene desaturase) and BraRGL1 (key DELLA protein) genes. We observed a loss-of-function mutation in BraRGL1 due to two amino acids in GRAS domain. BraRGL1 mutants displayed significantly increased time of flower bud differentiation and bolting. The expression of GA-regulatory protein (BraGASA6), flowering related genes (BraSOC1, BraLFY), expansion protein (BraEXPA11) and xyloglucan endotransferase (BraXTH3) genes was also significantly upregulated in these mutants. BraRGL1-overexpressing plants displayed the contrasting phenotypes. BraRGL1 mutants were more sensitive to GA signaling. BraRGL1 interacted with BraSOC1, and the interaction intensity decreased after GA3 treatment. In addition, BraRGL1 inhibited the transcription-activation ability of BraSOC1 for BraXTH3 and BraLFY genes, but the presence of GA3 enhanced the activation ability of BraSOC1, suggesting that the BraRGL1-BraSOC1 module regulates bolting and flowering of B. rapa through GA signal transduction. Thus, we hypothesized that BraRGL1 is degraded, and BraSOC1 is released in the presence of GA3, which promotes the expression of BraXTH3 and BraLFY, thereby inducing stalk development in B. rapa. Further, the BraRGL1-M mutant promoted the flower bud differentiation without affecting the stalk quality. Thus, BraRGL1 can serve as a valuable target for the molecular breeding of early maturing varieties."
Authors: Lijuan Zhao, Shengnan Li, Qingyang Yu, Chunxue Zhang, Liumin Wang, Yichen Jiang,Zedong Wu and Zhi Pi.
Agronomy (2023)
Abstract: To understand the relationship between vernalization and endogenous phytohormones on bolting, phytohormone levels and transcriptome changes were measured by LC-MS/MS and RNA sequencing before vernalization (CK), at the end of 16 weeks of vernalization (Vel) and at 5 days after vernalization (Re). A total of 32 phytohormone compounds significantly changed after vernalization; especially, the content of abscisic acid (ABA) and jasmonic acid (JA) was dramatically decreased more than sixteen and three times in the Vel and Re samples. In addition, GA19 accumulated after vernalization, while the content of GA53 and GA20 decreased. A total of 7471 differentially expressed genes (DEGs) were identified in response to vernalization. These DEGs were enriched with GO terms including response to stimulus (GO:0050896), response to hormone (GO:0009725) and shoot system development (GO:0048367). KEGG mapping indicated that 16, 13 and 11 DEGs were involved in gibberellic acid (GA), ABA and JA biosynthesis, suggesting a negative role of vernalization in phytohormone biosynthesis. Vernalization also repressed the expression of BvABFs and BvMYC2s, implying the inhibition of ABA and JA signalling. Additionally, vernalization plays a positive role in GA signalling, owing to the down-regulation of BvDELLAs. We also found that GA3-induced bolting could be retarded by exogenous ABA and methyl jasmonate (MeJA). In total, our results suggest that vernalization can promote GA-induced bolting by decreasing BvDELLA repressors of GA signalling and eliminating the antagonistic effects of ABA and JA.
Authors: Yufei Liang, Jiayu Bai, Zhilong Xie, Zhaoyuan Lian, Jia Guo, Feiyang Zhao, Yan Liang, Heqiang Huo and Haijun Gong.
Plant Physiology (2022)
Abstract: "The functions of sucrose transporters (SUTs) differ among family members. The physiological function of SUT1 has been studied intensively, while that of SUT4 in various plant species including tomato (Solanum lycopersicum) is less well understood. In this study, we characterized the function of tomato SlSUT4 in the regulation of flowering using a combination of molecular and physiological analyses. SlSUT4 displayed transport activity for sucrose when expressed in yeast (Saccharomyces cerevisiae), and it localized at both the plasma membrane and tonoplast. SlSUT4 interacted with SlSUT1, causing partial internalization of the latter, the main phloem loader of sucrose in tomato. Silencing of SlSUT4 promoted SlSUT1 localization to the plasma membrane, contributing to increased sucrose export and thus increased sucrose level in the shoot apex, which promoted flowering. Both silencing of SlSUT4 and spraying with sucrose suppressed gibberellin biosynthesis through repression of ent-kaurene oxidase and gibberellin 20-oxidase-1 (two genes encoding key enzymes in gibberellin biosynthesis) expression by SlMYB76, which directly bound to their promoters. Silencing of SlMYB76 promoted gibberellin biosynthesis. Our results suggest that SlSUT4 is a functional sucrose transporter in tomato; down-regulation of SlSUT4 expression enhances sucrose transport to the shoot apex, which promotes flowering by inhibiting gibberellin biosynthesis."
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Authors: Yong Zhou, Jingju Chen, Yaqi Hu, Lingdi Xiao, Zhaoyang Hu, Yuelong Zhou and Shiqiang Liu.
Journal of Plant Growth Regulation (2024)
Abstract: "DELLAs are known as negative regulators of gibberellin (GA) signaling pathway and control many aspects of plant development. In recent years, DELLA family genes were widely studied in many plant species, but little was known about the biological functions of DELLA genes in cucumber. In this study, genome-wide identification of the DELLA gene family members was performed (CsDELLA1–4), and their phylogenetic relationship, conserved motif, gene structure, cis-regulatory elements, and expression pattern were systematically analyzed. Amongst them, CsDELLA1 encoded a protein-harbored DGLLA, LERLE, and less-conserved TVHYNP motif in its N-terminal DELLA domain, implying the possible role of CsDELLA1 in GA-regulated growth and development. As anticipated, silenced CsDELLA1 by virus-induced gene silencing resulted in increased plant height and early flowering phenotypes. In contrast, overexpression of CsDELLA1 in Arabidopsis resulted in dwarf, late flowering, and inhibited hypocotyl elongation phenotypes, indicating that overexpression of CsDELLA1 inhibited the GA response in Arabidopsis. The transgenic plants also produced more buds and shorter siliques than the wild-type (WT) plants, and displayed a significantly longer primary root length than that of WT under exogenous GA3 treatment. Collectively, these results indicated that the CsDELLA1 might play important roles in regulation of GA-mediated growth and development."
Authors: Ping Huang, Jie Yang, Jiapeng Ke, Li Cai, Yingxiong Hu, Jun Ni, Chaoqiong Li, Zeng-Fu Xu and Mingyong Tang.
Plant Science (2024)
Highlights • GA4+7 and GA synthase gene JcGA20ox1 suppressed flowering in Jatropha, whereas the GA biosynthesis inhibitor paclobutrazol and GA degradation gene JcGA2ox6 promoted flowering. • JcGA20ox1 decreased the expression of JcFT; while, the inhibition of floral transition by JcGA20ox1 could restored by JcFT, and the seed yield suppression phenotype could partially restored by JcFT. • JcGA20ox1 also decreased JiFT expression and delayed floral transition in J. curcas × J. integerrima hybrids.
Abstract: "Jatropha curcas is a perennial oil-seed plant with vigorous vegetative growth but relatively poor reproductive growth and low seed yield. Gibberellins (GA) promote flowering in most annual plants, but inhibit flower initiation in many woody plants, including J. curcas. However, the underlying mechanisms of GA inhibition on flowering in perennial woody plants remain unclear. Here, we found that overexpression of the gibberellin biosynthesis gene JcGA20ox1 delays flowering in J. curcas and in the J. curcas × J. integerrima hybrids. Consistent with this finding, overexpression of the GA catabolic gene JcGA2ox6 induces early flowering in J. curcas. qRTsingle bondPCR revealed that the inhibition of floral transition by overexpressing JcGA20ox1 resulted from the decreased of JcFT and other flowering related genes, which was restored by overexpressing JcFT in J. curcas. Overexpression of JcGA20ox1 or JcGA2ox6 reduced seed yield, but overexpression of JcFT significantly increased seed yield. Furthermore, hybridization experiments showed that the reduction in seed yield caused by overexpression of JcGA20ox1 or JcGA2ox6 was partially restored by the overexpression of JcFT. In addition, JcGA20ox1, JcGA2ox6 and JcFT were also found to be involved in the regulation of seed oil content and endosperm development. In conclusion, our study revealed the inhibitory effect of GA on flowering in J. curcas is mediated through JcFT and demonstrated the effects of JcGA20ox1, JcGA2ox6 and JcFT on agronomic traits. This study also indicates the potential value of GA metabolism genes and JcFT in breeding new varieties of woody oil-seed plants."
Authors: Xiaoxiao Li, Chuyu Lin, Chenghao Lan and Zeng Tao.
Journal of Experimental Botany (2024)
Abstract: "The timing of the developmental transition from the vegetative to the reproductive stages is critical for angiosperm and fine-tuned by the integration of endogenous factors and external environmental cues to ensure proper and successful reproduction. Plants have evolved sophisticated mechanisms to response to diverse environmental or stress signals, which may be mediated by plant hormones which coordinate their flowering time. Endogenous and exogenous phytohormones such as gibberellin (GA), auxin, cytokinin (CK), jasmonate (JA), abscisic acid (ABA), ethylene (ET), brassinosteroids (BR) and the cross-talk among them are critical for the precise regulating of flowering time. Recent studies on the model flowering plant Arabidopsis thaliana revealed that diverse transcription factors and epigenetic regulators play key roles in the phytohormones that regulate floral transition. This review aims to summarize current knowledge on the genetic and epigenetic mechanisms that underlying the phytohormone control of floral transition in Arabidopsis, offering insights into how these processes are regulated and their implications for plant biology."
Authors: Eilon Shani, Peter Hedden and Tai-ping Sun.
Plant Physiology (2024)
One-sentence summary: A historical overview of gibberellin research showcases important advances in our understanding of gibberellin metabolism, perception, signaling, and transport.
Abstract: "It has been almost a century since biologically active gibberellin (GA) was isolated. Here, we give a historical overview of the early efforts in establishing the GA biosynthesis and catabolism pathway, characterizing the enzymes for GA metabolism, and elucidating their corresponding genes. We then highlight more recent studies that have identified the GA receptors and early GA signaling components (DELLA repressors and F-box activators), determined the molecular mechanism of DELLA-mediated transcription reprogramming, and revealed how DELLAs integrate multiple signaling pathways to regulate plant vegetative and reproductive development in response to internal and external cues. Finally, we discuss the GA transporters and their roles in GA-mediated plant development."
Authors: Le-Le Chu, Wei-Xuan Zheng, Hai-Qiang Liu, Xing-Xing Sheng, Qing-Ye Wang, Yue Wang, Chun-Gen Hu and Jin-Zhi Zhang.
Plant Physiology (2024)
Abstract: "Flowering is an essential process in fruit trees. Flower number and timing have a substantial impact on the yield and maturity of fruit. Ethylene and gibberellin play vital roles in flowering, but the mechanism of coordinated regulation of flowering in woody plants by gibberellin and ethylene is still unclear. In this study, a lemon (Citrus limon L. Burm) 1-aminocyclopropane-1-carboxylic acid synthase gene (CiACS4) was overexpressed in Nicotiana tabacum and resulted in late flowering and increased flower number. Further transformation of citrus revealed that ethylene and starch content increased, and soluble sugar content decreased in 35S:CiACS4 lemon. Inhibition of CiACS4 in lemon resulted in effects opposite to that of 35S:CiACS4 in transgenic plants. Overexpression of the CiACS4-interacting protein ETHYLENE RESPONSE FACTOR3 (CiERF3) in Nicotiana tabacum resulted in delayed flowering and more flowers. Further experiments revealed that the CiACS4-CiERF3 complex can bind the promoters of FLOWERING LOCUS T (CiFT) and GOLDEN2−LIKE (CiFE) and suppress their expression. Moreover, overexpression of CiFE in Nicotiana tabacum led to early flowering and decreased flowers, and ethylene, starch, and soluble sugar contents were opposite to those in 35S:CiACS4 transgenic plants. Interestingly, CiFE also bound the promoter of CiFT. Additionally, GA3 and ACC treatments delayed flowering in adult citrus, and treatment with gibberellin and ethylene inhibitors increased flower number. ACC treatment also inhibited the expression of CiFT and CiFE. This study provides a theoretical basis for the application of ethylene to regulate flower number and mitigate the impacts of extreme weather on citrus yield due to delayed flowering."
Authors: Rashmi Garg, Hrishikesh Mahato, Upasana Choudhury, Ravindra S. Thakur, Pratima Debnath, Nasreen G. Ansari, Vidhu A. Sane, Aniruddha P. Sane.
Plant Biotechnology Journal (2024)
Abstract: "Faster vegetative growth and early maturity/harvest reduce plant life cycle time and are important agricultural traits facilitating early crop rotation. GA is a key hormone governing developmental transitions that determine growth speed in plants. An EAR-motif repressor, SlERF36 that regulates various growth transitions, partly through regulation of the GA pathway and GA levels, was identified in tomato. Suppression of SlERF36 delayed germination, slowed down organ growth and delayed the onset of flowering time, fruit harvest and whole-plant senescence by 10–15 days. Its over-expression promoted faster growth by accelerating all these transitions besides increasing organ expansion and plant height substantially. The plant life cycle and fruit harvest were completed 20–30 days earlier than control without affecting yield, in glasshouse as well as net-house conditions, across seasons and generations. These changes in life cycle were associated with reciprocal changes in expression of GA pathway genes and basal GA levels between suppression and over-expression lines. SlERF36 interacted with the promoters of two GA2 oxidase genes, SlGA2ox3 and SlGA2ox4, and the DELLA gene, SlDELLA, reducing their transcription and causing a 3–5-fold increase in basal GA3/GA4 levels. Its suppression increased SlGA2ox3/4 transcript levels and reduced GA3/GA4 levels by 30%–50%. SlERF36 is conserved across families making it an important candidate in agricultural and horticultural crops for manipulation of plant growth and developmental transitions to reduce life cycles for faster harvest."
Authors: Lei Wang, Canrong Ma, Shuanghua Wang, Fei Yang, Yan Sun, Jinxiang Tang, Ji Luo and Jianqiang Wu.
Plant Physiology (2023)
Abstract: "Touch induces marked morphological changes in plants, including reduced rosette diameters and delayed flowering, a process called thigmomorphogenesis. Previous studies have revealed that thigmomorphogenesis in Arabidopsis (Arabidopsis thaliana) results from touch-induced accumulation of jasmonic acid (JA) and GIBBERELLIN 2-OXIDASE7 (GA2ox7) transcripts, which encode a gibberellin (GA) catabolism enzyme, leading to reduced levels of active GAs. However, the mechanisms underlying thigmomorphogenesis remain uncharacterized. Here we showed that touch induces ethylene (ET) production in Arabidopsis. After touch treatment, ET biosynthesis and signaling mutants exhibited even greater thigmomorphogenic changes and more decreased GA4 contents than did wild-type plants. Biochemical analysis indicated that the transcription factor ETHYLENE INSENSITIVE3 (EIN3) of the ET pathway binds to the promoter of GA2ox8 (encoding another GA 2-oxidase performing the same GA modification as GA2ox7) and represses GA2ox8 transcription. Moreover, MYC2, the master regulator of JA signaling, directly promoted GA2ox7 expression by binding the MYC2 promoter. Further genetic analysis suggested that the ET and JA pathways independently control the expression of GA2ox8 and GA2ox7, respectively. This study reveals that the ET pathway is a novel repressor of touch-induced thigmomorphogenesis and highlights that the ET and JA pathway converge on GA catabolism but play opposite roles to fine-tune GA4 content during thigmomorphogenesis."
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: Hanyang Cai, Liping Liu, Suzhuo Ma, Mohammad Aslam and Yuan Qin.
Current Opinion in Plant Biology (2023)
Abstract: "Germline specification is a fundamental process in plant reproduction, and the Megaspore Mother Cell (MMC), is a critical cell that differentiates and develops into the female gametophyte. While numerous studies have investigated the molecular mechanisms underlying female germline specification, previous reviews have mainly focused on gene regulatory networks, epigenetic pathways, and small RNAs, neglecting the potential contribution of phytohormones to this process. This review aims to address this gap by highlighting recent advances in MMC formation and discussing the roles of specific phytohormones in female germline specialization. Here, we provide a comprehensive overview of the functions of phytohormones in the formation of MMC and their effects on female gametophyte development. Specifically, it examines the roles of gibberellins (GAs), brassinosteroids (BRs), auxins, and cytokinin, in MMC development. Understanding the function of phytohormones in MMC development is essential for comprehending the complex mechanisms underlying plant reproduction. This review adds valuable insights to the existing knowledge on MMC development, providing a new perspective for future research in the field of plant reproduction."
Authors: Chunyu Zhang, Mingyang Jian, Weijun Li, Xiani Yao, Cuirong Tan, Qian Qian, Yilong Hu, Liu Xu and Xingliang Hou.
The Plant Cell (2023)
Abstract: "Gibberellin (GA) plays a key role in floral induction by activating the expression of floral integrator genes in plants, but the epigenetic regulatory mechanisms underlying this process remain unclear. Here, we show that BRAHMA (BRM), a core subunit of the chromatin remodeling SWI/SNF complex that functions in various biological processes by regulating gene expression, is involved in GA signaling-mediated flowering via the formation of the DELLA-BRM-NF-YC module in Arabidopsis (Arabidopsis thaliana). DELLA, BRM, and NF-YC transcription factors interact with each other, and DELLA proteins promote the physical interaction between BRM and NF-YC proteins. This impairs the binding of NF-YCs to SOC1, a major floral integrator gene, to inhibit flowering. On the other hand, DELLA proteins also facilitate the binding of BRM to SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1). The GA-induced degradation of DELLA proteins disturbs the DELLA-BRM-NF-YC module, prevents BRM from inhibiting NF-YCs, and decreases the DNA binding ability of BRM, which promotes the deposition of H3K4me3 on SOC1 chromatin, leading to early flowering. Collectively, our findings show that BRM is a key epigenetic partner of DELLA proteins during the floral transition. Moreover, they provide molecular insights into how GA signaling coordinates an epigenetic factor with a transcription factor to regulate the expression of a flowering gene and flowering in plants."
Authors: Peng Jia, Rahat Sharif, Youmei Li, Tianbo Sun, Shikui Li, Xuemei Zhang, Qinglong Dong, Haoan Luan, Suping Guo, Xiaolin Ren and Guohui Qi.
International Journal of Biological Macromolecules (2023)
Abstract: "Apple growth and yield are largely dependent on plant height and flowering characteristics. The BELL1-like homeobox (BLH) transcription factors regulate extensive plant biological processes. However, the BLH-mediated regulation of plant height and flowering in apple remains elusive. In the current study, 19 members of the MdBLH family were identified in the apple genome. Segmental duplication and purifying selection are the main reasons for the evolution of the MdBLH genes. A BLH1-like gene, MdBLH14, was isolated and functionally characterized. The MdBLH14 was preferentially expressed in flower buds, and downregulated during the floral induction period. The subcellular localization in tobacco leaves indicated that MdBLH14 is a nuclear protein. Overexpression of MdBLH14 in Arabidopsis led to a significant dwarfing and late-flowering phenotype by hindering active GA accumulation. Additionally, MdKNOX19, another member of the TALE superfamily, physically interacts with MdBLH14 and synergistically inhibits the expression of MdGA20ox3. This is the first report on the function of the MdBLH14 from apple, and its mechanism involving plant flower induction and growth. The data presented here provide a theoretical basis for genetically breeding new apple varieties."
Authors: Li Chen, Chaojie Liu, Jinghong Hao, Shuangxi Fan and Yingyan Han.
Horticulture Research (2023)
One-sentence summary: We found that LsRGL1 directly binds to promoter LsWRKY70 and inhibits its transcriptional activation function, which further elucidates that GA pathway regulates ABA pathway and LsWRKY70 is a key component of ABA-mediated positive regulation of tethering signaling pathway.
Abstract: "A variety of endogenous hormone signals, developmental cues, and environmental stressors can trigger and promote leaf lettuce bolting. One such factor is gibberellin (GA), which has linked to bolting. However, the signaling pathways and the mechanisms that regulate the process have not been discussed in full detail. To clarify the potential role of GAs in leaf lettuce, significant enrichment of GA pathway genes was found by RNA-seq, among which the LsRGL1 gene was considered significant. Upon overexpression of LsRGL1, a noticeable inhibition of leaf lettuce bolting was observed, whereas its knockdown by RNA interference led to an increase in bolting. In situ hybridization analysis indicated a significant accumulation of LsRGL1 in the stem tip cells of overexpressing plants. The leaf lettuce plants stably expressing LsRGL1 were examined concerning differentially expressed genes through RNA-seq analysis, and the data indicated an enhanced enrichment of these genes in “plant hormone signal transduction” and “phenylpropanoid biosynthesis” pathways. Additionally, significant changes in LsWRKY70 gene expression were identified in COG functional classification. The results of the yeast one-hybrid, GUS, and BLI experiments showed that LsRGL1 proteins directly bind to the LsWRKY70 promoters. Silencing LsWRKY70 by VIGS can delay bolting, regulate the expression of endogenous hormones, ABA-linked genes, and flowering genes, as well as improve the nutritional quality of leaf lettuce. These results strongly associate the positive regulation of bolting with LsWRKY70 by identifying its vital functions in the GA-mediated signaling pathway. The data obtained in this research is invaluable for further experiments concerning the development and growth of leaf lettuce.
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