Global key players of chloroplast gene expression

叶绿体核糖核酸酶 E (RNE) 在许多转录本的加工中发挥着重要的关键作用，因此属于叶绿体中主要的 RNA 加工因子。通过拟南芥中的正向和反向遗传学以及标记方法与质谱相结合，我们最近鉴定了一种类降解体复合物（DLC），其中包含RNE、RNJ、一个解旋酶、两个可能具有核糖体外功能的核糖体蛋白和未知蛋白，如RHON1和五肽重复（PPR）蛋白。以前认为叶绿体中不存在降解体。人们发现必需的植物特异性 RHON1 蛋白与那些在 rne 和 rhon1 突变体中不能有效加工的 RNA 区域特异性结合。因此，我们假设 RHON1 可能通过将目标 RNA 传递到 DLC 来支持 RNE 的功能。有趣的是，rne 和 rhon1 突变体具有大量微小的叶绿体，在质体分裂中发挥着重要作用。质体基因表达的另一个全球参与者是苍白水芹 (PAC)。我们证明 PAC 直接与蛋白质和 RNA 相互作用。该项目旨在分析 RNE、RHON1 和 PAC 相互作用伙伴的功能和重要性，以确定 PAC 的精确 RNA 靶标，并研究 PAC 在质体基因表达中的假定调节作用以及 PAC 在核糖体组装中的功能。我们预计，未来对 DLC 和 PAC、它们在叶绿体内的划分和关联伙伴的研究将为叶绿体基因表达、分裂和发育提供新的线索。

The chloroplast Ribonuclease E (RNE) plays an important key role in processing of many transcripts and therefore belongs to the major RNA processing factors in chloroplasts. By means of forward and reverse genetics in Arabidopsis and tagging approaches in combination with mass spectrometry we recently identified a degradosome-like complex (DLC), which contains RNE, RNJ, one helicase, two ribosomal proteins with presumably extraribosomal functions and unknown proteins, like RHON1 and a pentatricopeptide repeat (PPR) protein. A degradosome was previously thought not to exist in chloroplasts. The essential and plant specific RHON1 protein was found to bind specifically to those RNA regions, which are not processed efficiently in rne and rhon1 mutants. Therefore, we hypothesize that RHON1 supports the function of RNE presumably by delivering the target RNAs to the DLC. Interestingly, rne and rhon1 mutants have numerous and tiny chloroplasts strongly supporting an important role in plastid division. Another global player in plastid gene expression is represented by pale cress (PAC). We showed that PAC directly interacts with proteins and RNA. This project aims to analyse the function and importance of interaction partners of RNE, RHON1 and PAC, to identify the precise RNA targets of PAC and to investigate a putative regulatory role in plastid gene expression and the function of PAC in ribosome assembly. We anticipate that future research on the DLC and PAC, their compartmentalization within the chloroplast and association partners will shed new light on chloroplast gene expression, division and development.