STELLO调节植物纤维素合酶复合体分泌过程的分子机理

Cellulose is one of the major components of plant cell wall, where it plays vital roles in many processes, such as plant morphogenesis and organ development. In addition, cellulose is critical for the important agronomic traits in crops, including resistance to lodging and resistance to disease and insect pests. Cellulose is synthesized by cellulose synthase (CesA) complexes (CSCs) at the surface of plasma membrane. Accordingly, plant cells need to efficiently secrete these complexes to plasma membrane. So far, little has been known about the molecular mechanisms that specifically regulate the secretion process of CSCs in plant cells. In the previous work, the applicant, together with collaborators, had identified a novel protein family that interacted with CesAs, the STELLO (STL) protein family. Impairment of the functions of STL proteins led to severe defect of CSC secretion. However, the exact molecular mechanism underlying this phenotype is unclear. In this proposal, we plan to continue the analysis of STL functions, and screen for their interacting proteins as well as downstream key factors. We aim to reveal the molecular mechanism by which STLs regulate the secretion process of CSCs in plant cells. This project will not only extend our understanding of STL functions, but also provide theoretical guidance for improving agronomic traits, such as resistance to lodging and disease and insect pests, in agriculture.

纤维素是植物细胞壁的重要组成成分，不仅在植物形态建成和器官发育等过程中起重要作用，还与植物尤其是农作物的抗倒伏性和抗病虫害能力等重要农艺性状密切相关。植物细胞纤维素由纤维素合酶复合体在细胞膜表面合成。为此，植物细胞需要将该复合体高效分泌到细胞膜上。然而，目前关于特异调节植物纤维素合酶复合体分泌过程的分子机理尚不清楚。申请人在之前的工作中，鉴定了一个新型纤维素合酶互作蛋白家族－STELLO（STL）。STL家族蛋白质的功能缺失导致纤维素合酶复合体分泌到细胞膜的速率显著下降，但具体作用机制有待深入研究。基于此，申请人拟综合利用多种技术手段进一步探究STL的功能，同时筛选和鉴定其互作蛋白和下游关键因子，最终阐明STL调节纤维素合酶复合体分泌过程的分子机理。本项目不但有助于我们全面了解STL的功能，也将为在农业上改良农作物抗倒伏和抗病虫害等重要农艺性状提供理论指导。

纤维素是植物细胞壁的主要成分之一，在决定植物细胞的形态和机械强度等特性中发挥重要作用。植物纤维素由纤维素合酶复合体在细胞膜表面合成。为此，植物细胞需要将该复合体高效分泌到细胞膜上。然而，目前植物纤维素合酶复合体分泌过程的分子调控机理还不清楚。在本项目中，我们基于STELLO（STL）家族蛋白特异地标记一类含有纤维素合酶的囊泡（SmaCC/MASC）的前期结果，综合利用细胞生物学、遗传学和药理学的技术手段，深入分析了STL定位的SmaCC/MASC的来源及其形成的分子调控机制。研究结果表明，STL标记的SmaCC/MASC源于高尔基体，由高尔基体经过出芽、形成丝状结构、丝状结构断裂等过程分泌产生；在这个过程中，STL蛋白促进高尔基体的出芽，CSI1锚定高尔基体丝状结构的端部，Myosin促进高尔基体向前运动使丝状结构断裂。此外，我们也建立了STL蛋白的互作蛋白网络。这些结果对于全面了解STL的功能和理解纤维素合酶复合体的分泌过程都具有重要的意义。