Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Science, South China Normal University, 510631, Guangzhou, China.
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
New Phytol. 2022 Jul;235(1):173-187. doi: 10.1111/nph.18121. Epub 2022 Apr 11.
Chloroplasts are hypersensitive to heat stress (HS). SUMOylation, a critical post-translational modification, is conservatively involved in HS responses. However, the functional connection between SUMOylation and chloroplasts under HS remains to be studied. The bioinformatics, biochemistry, and cell biology analyses were used to detect the SUMOylation statuses of Arabidopsis nuclear-encoded chloroplast proteins and the effect of SUMOylation on subcellular localization of these proteins under HS. PSBR, a subunit of photosystem II, was used as an example for a detailed investigation of functional mechanisms. After a global SUMOylation site prediction of nuclear-encoded chloroplast proteins, biochemical data showed that most of the selected candidates are modified by SUMO3 in the cytoplasm. The chloroplast localization of these SUMOylation targets under long-term HS is partially maintained by the SUMO ligase AtSIZ1. The HS-induced SUMOylation on PSBR contributes to the maintenance of its chloroplast localization, which is dependent on its chloroplast importation efficiency correlated to phosphorylation. The complementation analysis provided evidence that SUMOylation is essential for the physiological function of PSBR under HS. Our study illustrated a general regulatory mechanism of SUMOylation in maintaining the chloroplast protein importation during HS and provided hints for further investigation on protein modifications associated with plant organelles under stress conditions.
叶绿体对热应激（HS）高度敏感。SUMOylation 是一种关键的翻译后修饰，保守地参与 HS 反应。然而，SUMOylation 与 HS 下叶绿体之间的功能联系仍有待研究。本研究通过生物信息学、生物化学和细胞生物学分析，检测了拟南芥核编码叶绿体蛋白的 SUMOylation 状态，以及 SUMOylation 对这些蛋白在 HS 下亚细胞定位的影响。以 PSBR（光合系统 II 的一个亚基）为例，对功能机制进行了详细研究。在对核编码叶绿体蛋白进行全局 SUMOylation 位点预测后，生化数据表明，大多数选定的候选蛋白在细胞质中被 SUMO3 修饰。在长期 HS 下，这些 SUMOylation 靶标在叶绿体中的定位部分由 SUMO 连接酶 AtSIZ1 维持。HS 诱导的 PSBR 上的 SUMOylation 有助于其在叶绿体中的定位，这依赖于与其磷酸化相关的叶绿体导入效率。互补分析提供了证据，表明 SUMOylation 对于 PSBR 在 HS 下的生理功能是必不可少的。本研究说明了 SUMOylation 在 HS 期间维持叶绿体蛋白导入过程中的一般调控机制，并为进一步研究应激条件下与植物细胞器相关的蛋白修饰提供了线索。
