论文题目：Balance of chlorophyll synthesis and thylakoid protein quality control influences chloroplast development in var2
论文作者：Peiyi Wang , Lin Zhu , Xiaomin Wang , Yanan Zhai , Jiahui Zhong , Hongchang Zhang , Jingxia Shao , Xiayan Liu , Fei Yu , Yafei Qi
论文摘要：Filamentous temperature-sensitive H (FtsH) is one major protease for thylakoid protein quality control in photosynthetic organisms. Mutations of the AtFtsH2 subunit in Arabidopsis result in yellow variegated2 ( var2 ) mutants. Genetic screening of ENHANCER OF VARIEGATION loci ( EVR ) provides new insights into the role of FtsH in chloroplast development beyond the degradation of photodamaged D1 protein. Here, we uncover a novel function of EVR3, previously reported as ETHYLENE-DEPENDENT GRAVITROPISM-DEFICIENT AND YELLOW-GREEN1 (EGY1), in regulating chlorophyll biosynthesis by association with the H subunit of magnesium chelatase (CHLH). Additionally, we identify a new var2 enhancer mutant, evr4-1 , caused by a missense mutation in CHLH. The evr4-1 mutant shows a significant decline in accumulations of light-harvesting complexes (LHC) rather than in photosystem II core proteins, while evr3 evr4 double mutants exhibit synthetic lethal phenotypes accompanied by a drastic reduction in the accumulation of chlorophyll and LHC. Furthermore, disruption of the thylakoid protein sorting pathway mediated by the chloroplast Signal Recognition Particle 54kDa protein (cpSRP54) mitigates the chloroplast development defect in var2-4 evr4-1 . Our findings underscore the critical role of thylakoid FtsH for thylakoid protein quality control when chlorophyll biosynthesis is disrupted.
FtsH是光合生物类囊体蛋白质质量控制的关键蛋白酶之一。拟南芥AtFtsH2亚基的突变会导致黄白斑叶突变体（ var2 ）。通过筛选 VAR2 的增强子位点（ EVR ），我们发现FtsH在叶绿体发育中的作用中除降解光损伤PSII核心亚基D1蛋白的之外的功能。本研究揭示了EVR3（此前报道为乙烯依赖性向重力性缺失黄绿突变体EGY1）通过与镁螯合酶H亚基（CHLH）互作调控叶绿素生物合成的新功能。同时，我们鉴定出一个由CHLH错义突变引发的新的 var2 增强子突变体 evr4-1 。该突变体主要表现为捕光复合体（LHC）而非光系统II核心蛋白的显著减少，而 evr3 evr4 双突变体则呈现合成致死表型，伴随叶绿素与LHC的急剧减少。此外，破坏叶绿体信号识别颗粒54kDa蛋白（cpSRP54）介导的类囊体蛋白分选途径，能够缓解 var2-4 evr4-1 的叶绿体发育缺陷。我们的研究结果证实，当叶绿素生物合成受阻时，类囊体FtsH对维持类囊体蛋白质质量控制具有关键作用。
论文链接：https://doi.org/10.1093/jxb/eraf177