Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou, 450001, China.
State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, 455000, China.
Sci China Life Sci. 2020 Dec;63(12):1905-1917. doi: 10.1007/s11427-020-1728-9. Epub 2020 Jul 3.
Brassinosteroid (BR), a steroid phytohormone, whose signaling transduction pathways include a series of phosphorylation and dephosphorylation events, and GSK3s are the main negative regulator kinases. BRs have been shown to play vital roles in cotton fiber elongation. However, the underlying mechanism is still elusive. In this study, fibers of a BR-defective mutant Pagoda 1 (pag1), and its corresponding wild-type (ZM24) were selected for a comparative global phosphoproteome analysis at critical developmental time points: fast-growing stage (10 days after pollination (DPA)) and secondary cell wall synthesis stage (20 DPA). Based on the substrate characteristics of GSK3, 900 potential substrates were identified. Their GO and KEGG annotation results suggest that BR functions in fiber development by regulating GhSKs (GSK3s of Gossypium hirsutum L.) involved microtubule cytoskeleton organization, and pathways of glucose, sucrose and lipid metabolism. Further experimental results revealed that among the GhSK members identified, GhSK13 not only plays a role in BR signaling pathway, but also functions in developing fiber by respectively interacting with an AP2-like ethylene-responsive factor GhAP2L, a nuclear transcription factor Gh_DNF_YB19, and a homeodomain zipper member GhHDZ5. Overall, our phosphoproteomic research advances the understanding of fiber development controlled by BR signal pathways especially through GhSKs, and also offers numbers of target proteins for improving cotton fiber quality.
油菜素内酯（BR）是一种甾醇类植物激素，其信号转导途径包括一系列磷酸化和去磷酸化事件，而 GSK3s 是主要的负调控激酶。BR 已被证明在棉花纤维伸长中发挥重要作用。然而，其潜在的机制仍不清楚。在这项研究中，选择了 BR 缺陷突变体 Pagoda1（pag1）及其相应的野生型（ZM24）的纤维，在关键发育时间点进行了比较的全局磷酸化组分析：快速生长阶段（授粉后 10 天（DPA））和次生细胞壁合成阶段（20 DPA）。根据 GSK3 的底物特征，鉴定了 900 个潜在的底物。它们的 GO 和 KEGG 注释结果表明，BR 通过调节 GhSKs（陆地棉 Gossypium hirsutum L. 的 GSK3s）参与微管细胞骨架组织和葡萄糖、蔗糖和脂质代谢途径，在纤维发育中发挥作用。进一步的实验结果表明，在所鉴定的 GhSK 成员中，GhSK13 不仅在 BR 信号通路中发挥作用，而且还通过分别与一个 AP2 样乙烯响应因子 GhAP2L、一个核转录因子 Gh_DNF_YB19 和一个同源域拉链成员 GhHDZ5 相互作用，在发育纤维中发挥作用。总的来说，我们的磷酸化组学研究推进了对 BR 信号通路控制纤维发育的理解，特别是通过 GhSKs，也为提高棉花纤维品质提供了许多目标蛋白。
