齐亚飞等《PLANT CELL AND ENVIRONMENT》2022年

论文题目：VAR2/AtFtsH2 and EVR2/BCM1/CBD1 synergistically regulate the accumulation of PSII reaction center D1 protein during de-etiolation in Arabidopsis

论文作者：Xiaomin Wang，Qinglong Li，Yalin Zhang，Mi Pan，Ruijuan Wang，Yifan Sun，Lijun An，Xiayan Liu，Fei Yu，Yafei Qi

论文摘要：Thylakoid FtsH complex participates in PSII repair cycle during high light-induced photoinhibition. The Arabidopsis yellow variegated2 (var2) mutants are defective in the VAR2/AtFtsH2 subunit of thylakoid FtsH complex. Taking advantage of the var2 leaf variegation phenotype, dissections of genetic enhancer loci have yielded novel paradigms in understanding functions of thylakoid FtsH complex. Here, we report the isolation of a new var2 enhancer, enhancer of variegation2-1 (evr2-1). We confirmed that EVR2 encodes a chloroplast protein that was known as BALANCE OF CHLOROPHYLL METABOLISM 1 (BCM1), or CHLOROPHYLL BIOSYNTHETIC DEFECT 1 (CBD1). We showed that EVR2/BCM1/CBD1 was involved in the oligomerization of photosystem I complexes. Genetic assays indicated that general defects in chlorophyll biosynthesis and the accumulation of photosynthetic complexes do not necessarily enhance var2 leaf variegation. In addition, we found that VAR2/AtFtsH2 is required for the accumulation of photosynthetic proteins during de-etiolation. Moreover, we identified PSII core proteins D1 and PsbC as potential EVR2-associated proteins using Co-IP/MS. Furthermore, the accumulation of D1 protein was greatly compromised in the var2-5 evr2-1 double mutant during de-etiolation. Together, our findings reveal a functional link between VAR2/AtFtsH2 and EVR2/BCM1/CBD1 in regulating chloroplast development and the accumulation of PSII reaction center D1 protein during de-etiolation.

类囊体膜FtsH复合体参与高光下光系统II的损伤与修复。目前我们对于其他调控因子是否与FtsH共同参与光系统II的生物发生尚不明确。使用拟南芥FtsH2突变体var2 特有的“花斑”叶色表型，通过遗传筛选获得var2“花斑”叶色的增强突变体(EVR，enhancer of variegation)，能够帮助理解类囊体膜FtsH参与的光系统II 生物发生与修复过程，以及叶绿体发育的调控机制。该研究鉴定了一个新的var2“花斑”叶色增强突变体evr2-1。图位克隆表明EVR2 编码定位于叶绿体膜上的叶绿素合成调控蛋白BCM1/CBD1 (Balance of Chlorophyll Metabolism 1/Chlorophyll Biosynthetic Defect 1)。 EVR2缺失影响到光系统I核心复合体向光系统I的聚合。遗传分析表明一般的叶绿素合成受阻以及光系统组装缺陷突变体不能够增强var2“花斑”叶色。此外，该研究还发现拟南芥FtsH2参与到去黄化过程中光合作用蛋白的积累。通过免疫共沉淀和质谱，该研究鉴定到EVR2可能与光系统II核心亚基D1和PsbC相互作用。进一步地去黄化实验表明，var2-5 evr2-1 双突变体中D1蛋白积累速率显著下降。这些表明VAR2/AtFtsH2和EVR2协同调控拟南芥去黄化过程中光系统II反应中心蛋白D1的积累。

文章链接：https://onlinelibrary.wiley.com/doi/10.1111/pce.14368