Regulation of thylakoid protein phosphorylation: Characterization of novel enzymes, mechanisms and physiological relevance for acclimation to light changes

光收集复合物II （LHCII）和PSII核心蛋白的磷酸化分别需要STN7和STN8激酶。LHCII的去磷酸化依赖于磷酸酶TAP38。PSII核心蛋白磷酸酶和另外一个PSII核心蛋白激酶仍有待鉴定。其他开放的基本问题涉及LHCII和PSII核心蛋白磷酸化的实际生理相关性，以及STN7的调节机制，以及STN7介导与长期光合驯化（LTR）相关的基因表达变化。此外，尽管类囊体超微结构的调节需要STN8，但我们发现这一过程不需要PSII核心蛋白磷酸化。为了鉴定PSII核心蛋白磷酸酶和额外的PSII核心蛋白激酶，我们将结合基因组学和亚细胞定位实验。为了阐明类囊体蛋白磷酸化的实际生理作用，我们将详细描述已知类囊体蛋白激酶和磷酸酶的突变体和过表达系。此外，我们将鉴定和表征那些赋予STN8超微结构变化的底物。在初步实验中，我们发现STN7丰度与LHCII磷酸化相关；因此，我们将在转录物和蛋白水平上分析STN7的表达。为了确定介导LTR信号的STN7底物以及LTR靶基因，将采用比较叶绿体磷蛋白质组和全基因组转录组分析。

Phosphorylation of the light-harvesting complex II (LHCII) and PSII core proteins requires the kinases STN7 and STN8, respectively. LHCII dephosphorylation depends on the phosphatase TAP38. The PSII core protein phosphatase and an additional PSII core protein kinase still await their identification. Other open fundamental questions concern the actual physiological relevance of LHCII and PSII core protein phosphorylation, and the mechanisms by which STN7 is regulated and by which STN7 mediates the gene expression changes associated with the long-term photosynthetic acclimation (LTR). Moreover, although STN8 is re-quired for modulation of thylakoid ultrastructure, we found that this process does not require PSII core protein phosphorylation. To identify the PSII core protein phosphatase and the additional PSII core protein kinase we will combine genomics and subcellular localisation experiments. To clarify the actual physiological role of thylakoid protein phosphorylation we will characterise in detail mutants and overexpressor lines for the known thylakoid protein kinases and phosphatases. Moreover, we will identify and characterize those substrates of STN8 that confer the ultrastructural changes. In preliminary experiments we found that STN7 abundance and LHCII phosphorylation correlate; therefore, we will analyse STN7 expression at the transcript and protein level. To identify the substrate of STN7 that mediates LTR signalling, as well as the LTR target genes, comparative chloroplast phosphoproteome and whole-genome transcriptome analyses will be em-ployed.