Brassinosteroids enhance gibberellic acid biosynthesis to promote cotton fibre cell elongation
油菜素内酯促进赤霉素生物合成促进棉花纤维细胞伸长
- 关键词：
- 来源：
- PLANT BIOTECHNOLOGY JOURNAL
- 类型：
- 学术文献
- 语种：
- 英语
- 原文发布日期：
- 2025-01-23
- 摘要：
- Cotton serves as not only a crucial natural textile crop, with cotton fibre accounting for approximately 95% of fibre usage in the textile industry but also a valuable model for the investigation of plant cell elongation (Cao et al., 2020; Wang et al., 2019). The plant hormones brassinosteroid (BR) and gibberellic acid (GA) promote fibre cell development (He et al., 2024; Huang et al., 2021; Shan et al., 2014; Zhu et al., 2023). Despite the positive role of BR and GA in fibre cell development that has been reported, the cross-talk between BR and GA biosynthesis pathway and signalling pathway in fibre growth remains largely unknown. In this study, our results reveal that BR stimulates GA biosynthesis during fibre elongation in cotton.BR and GA considerably promote cotton fibre development, whereas their respective inhibitors, brassinazole (BRZ, a BR biosynthesis inhibitor) and paclobutrazol (PAC, a GA biosynthesis inhibitor), impede fibre growth (Yang et al., 2023; Zhu et al., 2022). To explore the potential regulatory mechanisms between BR and GA, we treated wild-type (WT) ovules to with BR, BRZ, GA3, and PAC using an in vitro ovule culture system. Our observations reveal that BR and GA improved fibre development, and BRZ and PAC impeded it. In addition, GA3 mitigated the inhibitory effects of BRZ on fibre development, whereas PAC treatment considerably inhibited the fibre-promoting effect of BR. Moreover, the GA levels were increased after the BR treatment and decreased after the BRZ treatment (ovule with fibres). BES1 (Gh_D02G0939) is the critical regulator in BR signalling (Zhu et al., 2023). Overexpression of BES1 notably stimulated the GA content in fibres, accompanied with the considerably increased fibre length . PAC significantly inhibited the promotion of fibre length after BES1 overexpression. These results suggest that BR acts upstream of GA in the context of fibre development.In upland cotton, we identified 26 GA synthesis genes and 15 of them harboured BES1 binding site (E-box cis-element) in their promoters. The interaction between BES1 and 15 candidate gene promoters was investigated using yeast one-hybrid assay. As a result, BES1 was able to interact with two gene promoters (pGA20OX1D and pGA3OX1D). The tobacco dual-luciferase assay demonstrated that BES1 activated the promoters of GA20OX1D and GA3OX1D, which resulted in enhanced expression of LUC gene. The promoters of GA20OX1D and GA3OX1D were segmented into three fragments based on the distribution of E-box cis-elements. BES1 was found to specifically bind to the P2 and F3 fragments of the GA20OX1D and GA3OX1D promoters, respectively. Notably, this binding interaction was abolished upon mutation of the first E-box within the P2 or F3 fragments. Furthermore, the electrophoretic mobility shift assay revealed the specific binding affinity of BES1 to pGA20OX1D-L1 and pGA3OX1D-L2 fragments with the E-box. In addition, competitive binding probes, without biotin, considerably reduced the binding of BES1 protein to pGA20OX1D-L1 and pGA3OX1D-L2, respectively. Moreover, chromatin immunoprecipitation (ChIP) followed by sequencing and ChIP-quantitative PCR (qPCR) analysis demonstrated that BES1 was selectively recruited to the promoter fragments that contain the E-box. The expression levels of GA20OX1D and GA3OX1D in fibres were significantly increased after BR treatment or overexpression of BES1, and decreased after BRZ treatment or knockout of BES1. Furthermore, the expression levels of GA20OX1D and GA3OX1D were increased during cotton fibre development, suggesting the functional roles of these genes in fibre cell development.To further investigate the roles of GA20OX1D and GA3OX1D in cotton fibre development, GA20OX1D and GA3OX1D transgenic cotton plants were generated. Furthermore, we detected the GA content in GA20OX1D and GA3OX1D transgenic cotton fibres and found that overexpression of GA20OX1D or GA3OX1D increased GA accumulation. The fibre length was substantially increased in GA20OX1D or GA3OX1D overexpression plants and significantly decreased in knockout lines. In addition, the cell wall thickness of fibres was largely enhanced in GA3OX1D overexpression lines and reduced in GA3OX1D knockout lines. However, the cell wall thickness of fibres from GA20OX1D transgenic lines was comparable with that from WT plants. More importantly, exogenous application of GA3 successfully rescued the short fibre phenotype resulted from the mutation of GA20OX1D or GA3OX1D. Conversely, PAC inhibited the promotion of fibre elongation led by the overexpression of GA20OX1D or GA3OX1D. Previous studies indicate that GA facilitates cotton fibre elongation by enhancing the biosynthesis of very long-chain fatty acids (VLCFAs) (He et al., 2024; Tian et al., 2022; Xiao et al., 2016). We speculate that GA20OX1D and GA3OX1D may enhance fibre elongation by regulating the biosynthesis of VLCFAs. Collectively, our results illustrate that BR modulates the transcription of GA20OX1D and GA3OX1D via BES1, which in turn regulates GA biosynthesis to facilitate fibre development.
- 所属专题：
- 171
