高等植物种子是贮藏营养、繁育和传播后代的重要器官。同时，种子大小是决定作物产量的重要农艺性状之一。近年来，种子大小的调控途径研究取得很大进展，但对微管细胞骨架调控种子大小的作用机制还不清楚。在前期工作中，申请人在拟南芥中发现了一个新的种子大小调控基因Long Seed1（LSE1）。LSE1表达激活促进种子变大、角果增长。LSE1编码一个新的植物微管结合蛋白，并与微管排布调控的关键蛋白KTN1互作。本项目将通过三方面工作，明确LSE1如何调控种皮细胞和角果表皮细胞伸长过程中微管的排布变化；解析LSE1与KTN1互作对微管排布动态变化的影响，鉴定LSE1-KTN1复合体中的其他蛋白组分；综合正反向遗传学方法，构建LSE1介导的调控种子大小的基因互作网络。这些工作将阐明LSE1通过调控微管细胞骨架促进种子增大的分子机制，为人工调控种子大小提供新的知识和基因资源。

In higher plants, seed is one of the most important organs for nutrient storage and offspring propagation. Meanwhile, seed size is one of the determining factors of crop yield. In the recent years, tremendous progress has been made in understanding the molecular pathways that regulate seed size. However, little is known about the role of microtubule cytoskeleton in regulating seed size. In our previous work, we have identified a new gene involved in seed size regulation, LONG SEED1 (LSE1). Activated expression of LSE1 leads to larger seeds and longer siliques. LSE1 encodes a novel plant microtubule-binding protein. LSE1 also interacts physically with KTN1, a key regulator of microtubule organization. Based on these findings, here we propose to carry out works on three fronts to understand how LSE1 regulates the organization of microtubules in silique pavement cells and integument cells during seed development; to analyze how the interaction between LSE1 and KTN1 affects the dynamic organization of microtubules; to identify other components in LSE1-KTN1 complex; and to establish the LSE1-mediated genetic network of seed size control by integrating forward and reverse genetic approaches. Our work will shine light on the molecular mechanisms of how LSE1 regulates seed size via interacting with microtubule cytoskeleton. This work will provide new insights and gene resources for artificial manipulation of grain size in crops.