Molecular Physiology of Endosperm-limited Seed Germination - Gene Function and Regulation in the Endosperm of Brassicaceae Species

大多数被子植物的成熟种子都是胚乳，在许多情况下，覆盖胚根的微孔胚乳是胚胎膨胀和种子萌发的机械约束。通过对拟南芥（Lepidium sativum, Lepidium，大种子）和拟南芥（Arabidopsis）的跨种研究表明，胚乳弱化是这些芸苔科物种的一个重要特征。我们利用种子组织特异性转录组分析、遗传转化、qRT-PCR、萌发生理学、细胞壁生化、逆向遗传学和生物力学等方法，将Lepidium建立为跨学科种子研究的模型系统。我们的新工作计划包括利用我们的种子组织特异性转录组识别和分析组织特异性启动子用于反向遗传学和qRT-PCR的优质管家基因用于种子研究。我们希望进一步优化我们的Lepidium种子反向遗传技术。两种组织特异性的反向遗传学方法以GA受体GID1（上游，信号传导）和果胶修饰酶作为蛇皮草胚乳弱化的下游机制为靶点。果胶介导的机制属于后期弱化机制。早期时间点的胚乳特异性cDNA文库和组织特异性跨物种转录组分析将用于鉴定早期胚乳弱化靶点。本项目旨在通过对胚乳弱化上下游机制的转基因种子进行功能和生物力学分析，为胚乳在种子萌发过程中的功能提供新的认识。

The mature seeds of most angiosperm species are endospermic and in many cases the micropylar endosperm that covers the radicle is a mechanical constraint to embryo expansion and seed germination. We have shown by cross-species work with Lepidium sativum (Lepidium, big seeds) and Arabidopsis that endosperm weakening is an important trait of these Brassicaceae species. We have used seed-tissue-specific transcriptome analysis, genetic transformation, qRT-PCR, germination physiology, cell-wall biochemistry, reverse-genetics, and biomechanics to establish Lepidium as a model system for interdisciplinary seed research. Our new work plan includes as goals to identify and analyse tissue-specific promoters for reverse-genetics and superior housekeeping genes for qRT-PCR for seed research by utilizing our seed-tissue-specific transcriptome. We want to further optimize our reverse-genetics techniques for Lepidium seeds. Two tissue specific reverse-genetics approaches have the GA receptor GID1 (upstream, signaling) and pectin modifying enzymes as downstream mechanism for Lepidium endosperm weakening as targets. Pectin-mediated mechanism(s) belong to the late weakening mechanisms. Endosperm-specific cDNA libraries and tissue-specific cross-species transcriptome analysis at early time points will be used to identify early endosperm weakening targets. This project aims to deliver transgenic seeds altered in upstream and downstream mechanisms of endosperm weakening for functional and biomechanical analysis and will provide novel insight into endosperm function during seed germination.