Environmental information perceived by chloroplasts can be translated into retrograde signals that alter the expression of nuclear genes. Singlet oxygen (¹O₂) generated by photosystem II (PSII) can cause photo-oxidative damage of PSII but has also been implicated in retrograde signaling. We previously reported that a nuclear-encoded chloroplast FtsH2 metalloprotease coordinates ¹O₂-triggered retrograde signaling by promoting the degradation of the EXECUTER1 (EX1) protein, a putative ¹O₂ sensor. Here, we show that a ¹O₂-mediated oxidative post-translational modification of EX1 is essential for initiating ¹O₂-derived signaling. Specifically, the Trp643 residue in DUF3506 domain of EX1 is prone to oxidation by ¹O₂. Both the substitution of Trp643 with ¹O₂-insensitive amino acids and the deletion of the DUF3506 domain abolish the EX1-mediated ¹O₂ signaling. We thus provide mechanistic insight into how EX1 senses ¹O₂ via Trp643 located in the DUF3506 domain.

叶绿体感知到的环境信息可以转化为逆向信号，从而改变核基因的表达。由光系统II（PSII）产生的单线态氧（¹ O ₂）可以引起PSII的光氧化损伤，但也与逆行信号有关。我们以前曾报道过，核编码的叶绿体FtsH2金属蛋白酶通过促进EXECUTER1（EX1）蛋白（一种可能的¹ O ₂传感器）的降解来协调¹ O ₂触发的逆行信号。在这里，我们表明EX ^1的1 O ₂介导的氧化后翻译修饰对于启动¹ O是必不可少的₂派生的信令。具体而言，EX1的DUF3506结构域中的Trp643残基易于被¹ O ₂氧化。用¹ O _2不敏感的氨基酸取代Trp643和删除DUF3506域都消除了EX1介导的¹ O ₂信号传导。因此，我们提供了有关EX1如何通过位于DUF3506域中的Trp643感测¹ O _2的机制的见解。