Du Yanxin, Li Yang, Tang Weijiang, Mo Weiping, Ma Tingting, Lin Rongcheng
Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
Biotechnology Institute, Xianghu Laboratory, Hangzhou, China.
Plant Biotechnol J. 2025 Jul;23(7):2931-2948. doi: 10.1111/pbi.70101. Epub 2025 May 7.
Chloroplast development is fundamental to photosynthesis and plant growth but is sensitive to environmental stress. Chloroplast development and division require genome stability and DNA repair, but the underlying mechanisms have been unclear. Using a forward genetic approach, we identified the striped-leaf mutant k48 in the rice (Oryza sativa L. japonica) cultivar KY131 background. k48 displayed defects in chloroplast development and photosynthesis, especially under high-light conditions. Genetic and complementation studies revealed that the loss of ESSENTIAL MEIOTIC ENDONUCLEASE 1 (EME1) is responsible for the defects in k48. Transcriptomic analysis showed that OsEME1 globally regulates the expression of genes involved in photosynthesis and DNA repair. Furthermore, mutations in OsEME1 led to cell cycle arrest and a DNA damage response. An in vitro endonuclease activity assay indicated that OsEME1 directly binds to and cleaves DNA substrates with a specific structure and that four conserved amino acids are required for its activity. Notably, OsEME1 targeted DNA fragments of rice GOLDEN-LIKE 1 (GLK1) and GLK2. We also demonstrated that OsEME1 interacts with the structure-specific endonuclease methyl methanesulfonate (MMS) and UV-SENSITIVE PROTEIN 81 (MUS81). This study highlights the role of OsEME1 in regulating chloroplast development by modulating homologous recombination repair in response to damage to double-stranded DNA.
叶绿体发育是光合作用和植物生长的基础，但对环境胁迫敏感。叶绿体发育和分裂需要基因组稳定性和DNA修复，但其潜在机制尚不清楚。我们采用正向遗传学方法，在水稻（Oryza sativa L. japonica）品种KY131背景中鉴定出条纹叶突变体k48。k48在叶绿体发育和光合作用方面存在缺陷，尤其是在高光条件下。遗传和互补研究表明，必需减数分裂内切核酸酶1（EME1）的缺失是k48缺陷的原因。转录组分析表明，OsEME1全局调控参与光合作用和DNA修复的基因表达。此外，OsEME1突变导致细胞周期停滞和DNA损伤反应。体外内切核酸酶活性测定表明，OsEME1直接结合并切割具有特定结构的DNA底物，其活性需要四个保守氨基酸。值得注意的是，OsEME1靶向水稻类黄金1（GLK1）和GLK2的DNA片段。我们还证明了OsEME1与结构特异性内切核酸酶甲磺酸甲酯（MMS）和紫外线敏感蛋白81（MUS81）相互作用。本研究强调了OsEME1在响应双链DNA损伤时通过调节同源重组修复来调控叶绿体发育中的作用。
