齐亚飞等《Journal of Biological Chemistry》2022年

论文题目：Chloroplast envelope ATPase PGA1/AtFtsH12 is required for chloroplast protein accumulation and cytosol-chloroplast protein homeostasis in Arabidopsis

论文作者：Qinglong Li (李青龙), Xiaomin Wang (王晓敏), Yang Lei (雷洋), Yanling Wang (王艳玲), Bilang Li (李碧浪), Xiayan Liu (刘夏燕), Lijun An (安丽君), Fei Yu (郁飞), Yafei Qi (齐亚飞)

论文摘要：The establishment of photosynthetic protein complexes during chloroplast development requires the influx of a large number of chloroplast proteins that are encoded by the nuclear genome, which is critical for cytosol and chloroplast protein homeostasis and chloroplast development. However, the mechanisms regulating this process are still not well-understood in higher plants. Here, we report the isolation and characterization of the pale greenArabidopsis pga1-1 mutant, which is defective in chloroplast development and chloroplast protein accumulation. Using genetic and biochemical evidence, we reveal that PGA1 encodes AtFtsH12, a chloroplast envelope-localized protein of the FtsH family proteins. We determined a G703R mutation in the GAD motif of the conserved ATPase domain renders the pga1-1 a viable hypomorphic allele of the essential gene AtFtsH12. In de-etiolation assays, we showed that the accumulation of photosynthetic proteins and the expression of photosynthetic genes were impaired in pga1-1. Using the FNRctp-GFP and pTAC2-GFP reporters, we demonstrated that AtFtsH12 was required for the accumulation of chloroplast proteins in vivo. Interestingly, we identified an increase in expression of the mutant AtFtsH12 gene in pga1-1, suggesting a feedback regulation. Moreover, we found that cytosolic and chloroplast proteostasis responses were triggered in pga1-1. Together, taking advantage of the novel pga1-1 mutant, we demonstrate the function of AtFtsH12 in chloroplast protein homeostasis and chloroplast development.

叶绿体发育过程中，细胞核基因组编码的大量的叶绿体光合作用相关蛋白转运至叶绿体。在高等植物中，虽然叶绿体蛋白转运对于细胞质和叶绿体蛋白质稳态以及叶绿体的发育至关重要，但是其调控过程仍不清楚。我们通过遗传筛选，获得了Pale Green Arabidopsis淡绿叶色突变体pga1-1，其光合作用蛋白的稳态积累明显降低。图位克隆及回复实验表明PGA1编码叶绿体被膜蛋白AtFtsH12。pga1-1突变体AtFtsH12的ATPase结构域中保守GAD模块的甘氨酸突变为带正电荷的精氨酸。pga1-1是叶绿体发育必需基因AtFtsH12可存活的亚效突变体。进一步利用35S过表达启动子驱动的能够定位于叶绿体的FNRcTP-GFP和自身启动子驱动的pTAC2-GFP 研究并明确了AtFtsH12参与叶绿体蛋白的稳态积累。pga1-1突变体中，除了AtFtsH12的表达量显著上调之外，参与蛋白稳态积累的细胞质分子伴侣ctHSP70、叶绿体分子伴侣cpHSP70和叶绿体蛋白酶ClpP1的表达量显著增加。这些证据表明叶绿体被膜AtFtsH12参与并影响叶绿体蛋白稳态积累。

文章链接：https://www.sciencedirect.com/science/article/pii/S0021925822009322