The Arabidopsis NOT4A E3 ligase coordinates PGR3 expression to regulate chloroplast protein translation
The Arabidopsis NOT4A E3 ligase coordinates PGR3 expression to regulate chloroplast protein translation
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DOI：
10.1101/2020.04.02.021998
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发表时间：
2020-04
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通讯作者：
Mark Bailey;Aiste Ivanauskaite;Julia Grimmer;Oluwatunmise Akintewe;Adrienne C. Payne;Ross D. Etherington;A. Labandera;Rory Osborne;Marjaana Rantala;S. Baginsky;P. Mulo;D. Gibbs
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作者：
Mark Bailey;Aiste Ivanauskaite;Julia Grimmer;Oluwatunmise Akintewe;Adrienne C. Payne;Ross D. Etherington;A. Labandera;Rory Osborne;Marjaana Rantala;S. Baginsky;P. Mulo;D. Gibbs
叶绿体的功能需要核和叶绿体衍生蛋白的协调作用，包括数百种核编码的五肽重复（PPR）蛋白，这些蛋白调节质体mRNA的代谢。尽管它们数量众多且很重要，但控制PPR表达的调控机制尚不清楚。本研究表明，拟南芥NOT4A泛素连接酶正调控质子梯度3 (PGR3)， PGR3是一种PPR蛋白，用于翻译叶绿体内30S核糖体亚基和几种类囊体定位的光合成分。NOT4A功能的丧失导致质体核糖体的强烈耗损，减少mRNA的翻译，对光合能力产生负面影响，导致淡黄色和生长缓慢的表型。定量转录组和蛋白质组分析显示，这些缺陷是由于not4a中缺乏PGR3的表达，我们发现通过转基因PGR3表达可以恢复正常的质体功能。我们的研究发现NOT4A通过调节PGR3水平来协调叶绿体蛋白合成，在发育和应激反应过程中对确保强大的光合功能至关重要。
Chloroplast function requires the coordinated action of nuclear- and chloroplast-derived proteins, including several hundred nuclear-encoded pentatricopeptide repeat (PPR) proteins that regulate plastid mRNA metabolism. Despite their large number and importance, regulatory mechanisms controlling PPR expression are poorly understood. Here we show that the Arabidopsis NOT4A ubiquitin-ligase positively regulates PROTON GRADIENT 3 (PGR3), a PPR protein required for translating 30S ribosome subunits and several thylakoid-localised photosynthetic components within chloroplasts. Loss of NOT4A function leads to a strong depletion of plastid ribosomes, which reduces mRNA translation and negatively impacts photosynthetic capacity, causing pale-yellow and slow-growth phenotypes. Quantitative transcriptome and proteome analyses reveal that these defects are due to a lack of PGR3 expression in not4a, and we show that normal plastid function is restored through transgenic PGR3 expression. Our work identifies NOT4A as crucial for ensuring robust photosynthetic function during development and stress-response, through modulating PGR3 levels to coordinate chloroplast protein synthesis.