CDE6 Regulates Chloroplast Ultrastructure and Affects the Sensitivity of Rice to High Temperature

Chloroplasts are key organelles in plants that carry out photosynthesis, convert light energy into chemical energy, and synthesize organic compounds. In this study, a stably heritable chlorophyll-deficient mutant was screened from the ethyl methanesulfonate-induced mutation library of Wuyunjing 21 (WYJ21). This mutant was designated as chlorophyll deficient 6 (cde6). The cde6 mutant exhibits a low chlorophyll content, photosynthetic defects, an impaired chloroplast structure, a significant reduction in the number of stacked thylakoid layers, and a yellow-green leaf phenotype in the early tillering stage. Through MutMap analysis, it was found that the cde6 mutant harbors a single-base mutation (T→A) in the LOC_Os07g38300 gene. This mutation results in an amino acid substitution from valine (Val) to aspartic acid (Asp) in the encoded protein, thereby affecting the protein's structure and function. The mutation of CDE6 leads to decreased expression of genes related to chloroplast development and chlorophyll biosynthesis. Further studies revealed that the CDE6, a potential chloroplast ribosome recycle factor, leads to high temperature sensitivity in rice when mutated. As high-temperature stress is a primary constraint to global rice productivity, the identification of CDE6 provides a genetic target for improving thermotolerance. In conclusion, these findings demonstrate that CDE6 plays a crucial role in chloroplast biogenesis and provide new insights into its regulatory function in high-temperature tolerance.