Initiation of starch granules and regulation of the starch granule number per chloroplast in Arabidopsis thaliana

在过去的几年里，关于淀粉代谢的知识，特别是关于拟南芥的短暂淀粉代谢的知识，大大增加了。然而，一些根本性的问题仍然悬而未决。因此，淀粉粒是如何启动的，存在哪些调控过程，确实决定了每个叶绿体的淀粉粒数量。这对淀粉工业应用和生物技术也很重要。最近，两个拟南芥品系被鉴定出来，它们的叶绿体中的淀粉粒数量显著减少，ss4和dpe2/phs1。通过广泛的分析，我们发现存在不止一种淀粉起始途径。此外，我们还表明，淀粉颗粒的数量可以通过改变光/暗状态和改变淀粉的降解过程来改变。因此，这些突变体是更详细地分析淀粉起始过程的一个很好的工具。本研究采用不同的实验方法，主要集中在以下几个方面：1.详细分析PHS1和DPE2对淀粉颗粒形成的影响，通过改变光照条件，通过改变表达，通过表达这些酶的非活性版本来区分酶的代谢或结构功能，并通过确定蛋白质的相互作用伙伴。2.特定淀粉粒参数的分析。修改淀粉降解率，以确定淀粉降解率和淀粉粒起始之间的联系。

Over the last years the knowledge about starch metabolism, especially about the transitory starch metabolism in Arabidopsis thaliana, is tremendously increased. However, some fundamental questions are still open. Thus, how starch granules are initiated and which regulatory processed exist do determine the number of starch granules per chloroplast. This is also important for starch industrial applications and biotechnology. Recently, two Arabidopsis lines were identified which show a strong reduction in the number of starch granules in the chloroplast, ss4 and dpe2/phs1. Using extensive analyses we showed that more than one pathway of starch initiation exists. Furthermore, we showed that the number of starch granules can be altered by changes in the light/dark regime and by modification of the starch degradation process. Thus, these mutants are an excellent tool to analyse the process of starch initiation in more detail.This proposal uses various experimental approaches and focuses on the following aspects:1. Detailed analyses of PHS1 and DPE2 influences on starch granule formation, by altering the light regime, by alteration of the expression, by expression of inactive versions of these enzymes to distinguish between metabolic or structural functions of the enzymes, and by identify interaction partners of the proteins. 2. Analysis of the specific starch granule parameters3. Modify the starch degradation to identify the link between starch degradation and starch granule initiation.