The Arabidopsis YDL1 suppresses singlet oxygen-induced gene expression changes

Singlet oxygen (1O2), the main ROS produced in chloroplasts, has long been recognized as a cytotoxin that inhibits photosynthesis and damages the cell. However, more recent findings have proposed 1O2 as a highly versatile signal that induces various stress responses. A signaling role for 1O2 was first documented in the conditional fluorescent (flu) mutant of Arabidopsis. Release of 1O2 in flu mutant induces bleach/die of young seedlings and growth inhibition of mature plants. However, all these drastic phenotypic changes can be suppressed by mutation of EXCUTER1 (EX1) gene. The Arabidopsis YDL1 was identified during a screen of revertant mutant from EMS mutagenized flu/ex1. Loss of function of SAFE1 leads to highly expression of 1O2-indluced genes in flu/ex1 mutant, mimicking the flu mutant. We found that YDL1 localized in the stroma of chloroplast, and suppressed 1O2-mediated stress responses via inhibiting 1O2-induced damage on the grana margins. Overall design: Examination of differential gene expression in the Arabidopsis flu/ex1 and flu/ex1/ydl1 mutant before and after the release of 1O2