Functions of CURT1 proteins in thylakoid grana formation

陆地植物的叶绿体通常含有粒状的圆柱形类囊体膜。导致颗粒形成的机制，特别是产生颗粒边缘极端曲率的因素在很大程度上是未知的。在之前的工作中，我们已经确定了一个小的蛋白质家族，命名为CURT1，这是颗粒形成所必需的。由于CURT1蛋白的过表达增加了颗粒膜层的数量，CURT1蛋白在颗粒边缘高度富集，并且CURT1蛋白在体外可以诱导脂质体的管化，我们认为这些蛋白直接参与诱导/维持边缘膜曲率。本项目将解决的五个核心问题是：1。CURT1蛋白弯曲膜的机制是什么？2. 类囊体蛋白（包括CURT1）的磷酸化在颗粒堆积中的作用是什么？3. CURT1蛋白的颗粒堆叠功能是如何进化的？4. CURT1是否足以在体内介导颗粒堆积？还涉及哪些其他因素？5. 特别是在自然条件下，颗粒堆积的生理相关性是什么？为了解决这些问题，我们将运用分子遗传学、分子生物学、生物化学和电子显微镜（EM）的方法，研究几种模式物种，特别是拟南芥、聚囊藻6803和莱茵衣藻。

Chloroplasts of land plants characteristically contain grana, cylindrical stacks of thylakoid membranes. The mechanisms leading to the formation of grana, and in particular the factors that generate the extreme curvature in grana margins are largely unknown. In previous work we have identified a small family of proteins, designated CURT1, which is required for grana formation. Because overexpresion of CURT1 proteins increases the number of membrane layers in grana, the CURT1 proteins are highly enriched in grana margins, and CURT1 proteins can induce tubulation of liposomes in vitro, we conclude that these proteins are directly involved in inducing/maintained the membrane curvature in margins. The five central questions which will be addressed in this project are: 1. By which mechanism do CURT1 proteins bend membranes? 2. What is the role of phosphorylation of thylakoid proteins (including CURT1) in grana stacking? 3. How has the grana stacking function of CURT1 protein evolutionary developed? 4. Is CURT1 sufficient in vivo to mediate grana stacking? Which other factors are involved? 5. What is the physiological relevance, in particular under natural conditions, of grana stacking? To address these questions we will apply methods from molecular genetics, molecular biology, biochemistry and electron microscopy (EM) and study several model species, in particular Arabidopsis thaliana, Synechocystis 6803 and Chlamydomonas reinhardtii.