拟南芥CESA的磷酸化修饰调控细胞伸长生长的分子机制

Plant cell expansion and morphogenesis plays an important role in controlling plant size and shape. Understanding structure-function relationships of plant cell walls is essential for the study of plant cell expansion and morphogenesis. Our previous studies demonstrated that phosphorylation of some residues of cellulose synthase CESA1 and CESA3 play important roles in the control of cellulose biosynthesis and cell elongation, but the underlying mechanisms are still unclear. CESA1 and CESA3 have been identified to have dozens of phosphorylation sites. This study will start with an analysis of evolution of CESAs and their phosphorylation sites across species, along with quantitative phosphoproteome data mining and analysis, to identify the functional significance of various CESA phosphorylation sites and select the sites for further study. Phosphomimetic and non-phosphorylatable mutations of selected CESA phosphorylation sites will be constructed and examined for their effects on cellulose synthesis and cell elongation. Live cell imaging will be used to analyze bidirectional mobility of CESA movement along microtubules. Structural differences of mutant cell walls will be examined with previously established procedures using atomic forced and super-resolution microscopes. Profiling differences among CESA mutants in their functions and cell wall structures will help clarify the structure and function relationships of plant cell walls of the mutants as well as the underlying mechanisms of CESA phosphorylation to regulate plant cell expansion and morphogenesis. This study will make a significant contribution to our understanding of plant cell expansion and morphogenesis.

植物细胞生长过程对于其形态建成及发挥特定功能至关重要。阐明细胞壁结构与功能的关系是了解植物细胞生长和形态建成的关键。申请人在前期研究中发现，纤维素合成酶CESA1和CESA3部分位点的磷酸化修饰，在调控纤维素合成和细胞伸长生长方面有重要作用，然而相关机制尚未明确。拟南芥CESA1和CESA3有数十个磷酸化位点，本课题拟从CESA磷酸化位点的物种间进化关系及其蛋白组数据挖掘入手，揭示不同位点的功能意义，选定重点研究位点。针对所选位点，构建模拟磷酸化和去磷酸化突变体，通过表型分析，明确相关位点的功能。利用活细胞成像，测定微管引导的CESA复合体双向合成移动。结合突变体细胞壁的原子力和超分辨显微成像分析，明确不同位点的磷酸化对纤维素合成和细胞壁结构的影响，揭示细胞壁结构与功能的内在联系，阐明CESA的磷酸化修饰调控细胞伸长生长的分子机制。本研究对于探索植物细胞生长和形态建成具有重要意义。

植物细胞生长过程对于其形态建成及发挥特定功能至关重要。阐明细胞壁结构与功能的关系是了解植物细胞生长和形态建成的关键。纤维素合成酶CESA1和CESA3部分位点的磷酸化修饰，在调控纤维素合成和细胞伸长生长方面有重要作用，然而相关机制尚未明确。拟南芥CESA1和CESA3有数十个磷酸化位点，本研究从CESA磷酸化位点的物种间进化关系及其蛋白组数据挖掘入手，揭示了不同位点的功能意义，选定了重点研究位点。针对所选位点，构建了模拟磷酸化和去磷酸化突变体，通过表型分析，明确了相关位点的功能。定量蛋白组学分析表明，油菜素内酯（BRs）BR和脱落酸(ABA)等植物激素显著影响CESA1和CESA3的磷酸化修饰水平。相关位点的模拟磷酸化和去磷酸化突变体分析结果表明，CESA不同位点的磷酸化修饰正向或反向调控细胞伸长生长，并参与调控种子的发育，包括种子的大小和萌发，揭示了种子发育调控新机制。细胞壁分析结果表明，CESA的磷酸化修饰不仅调节纤维素合成，同时影响果胶的甲酯化修饰，揭示了揭示了细胞壁延展性调控新机制。前期研究表明，油菜素内酯信号通路的GSK3家族蛋白激酶参与催化CESA蛋白磷酸化。本研究进一步发现，油菜素内酯及其下游GSK3家族蛋白激酶介导糖信号调节黄化苗下胚轴的形态建成，结合相关CESA磷酸化位点的发掘，本研究为进一步揭示糖信号和油菜素内酯信号调控纤维素合成和植物细胞形态建成的分子机制奠定了重要基础。

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