Genetic Dissection of Organellar-Gene-Expression (OGE)-Dependent Retrograde Signaling in Arabidopsis

大多数质体蛋白是核编码的，它们的转录调控涉及逆行信号。化学物质如林可霉素或突变如prpl11或prors1对细胞器基因表达（OGE）的损害触发了逆行信号传导途径，并导致核光合基因的转录下调。对拟南芥prors1突变体的研究表明，当OGE受到干扰时，来自叶绿体和线粒体的信号协同下调核光合基因的表达。在之前的资助期间，我们已经产生了具有可抑制的OGE的品系，发现gun1突变覆盖了由prors1触发的OGE信号传导，并鉴定了第一个在prors1背景下具有去抑制的LHCB表达的rls（放松的LHCB抑制）突变体。在下一个资助期内，我们将从具有可抑制的OGE或GUN1活性的细胞系的转录组动力学出发，鉴定OGE和GUN1信号传导的靶基因。我们将对rls突变体进行分类和鉴定，并确定至少两个RLS基因。第三，我们将详细描述GUN1在OGE信号转导中的作用，考虑到GUN1与质体核糖体功能相互作用的可能性。这种组合策略将使我们能够识别参与叶绿体或线粒体信号传导的因子，以及整合两种信号传导途径活动的因子。

Most plastid proteins are nucleus-encoded and their transcriptional regulation involves retrograde signaling. Impairment of organellar gene expression (OGE) by chemicals such as lincomycin, or mutations such as prpl11 or prors1, trigger a retrograde signaling pathway and result in transcriptional down-regulation of nuclear photosynthetic genes. Work on the Arabidopsis prors1 mutant showed that when OGE is perturbed, signals derived from both chloroplasts and mitochondria cooperate in down regulating nuclear photosynthetic gene expression. In the previous funding period we have generated lines with repressible OGE, discovered that the gun1 mutation overrides OGE signaling triggered by prors1, and identified the first rls (relaxed LHCB repression) mutants with derepressed LHCB expression in the prors1 background. In the next funding period we will identify target genes of OGE and GUN1 signaling starting from transcriptome kinetics of lines with repressible OGE or GUN1 activity. We will classify and characterize the rls mutants and identify at least two RLS genes. Thirdly, we will characterize in detail the role of GUN1 in OGE signaling, considering the possibility that GUN1 functionally interacts with plastid ribosomes. This combined strategy will enable us to identify factors involved in chloroplast or mitochondrial signaling, as well as factors that integrate the activities of the two signaling pathways.