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

## TL;DR

A new rice mutant with yellow-green leaves was found to have a gene mutation affecting chloroplast structure and heat sensitivity.

## Contribution

The discovery of CDE6 as a genetic target for improving rice's tolerance to high temperatures.

## Key findings

- The cde6 mutant has reduced chlorophyll, photosynthetic defects, and impaired chloroplast structure.
- A single-base mutation in LOC_Os07g38300 causes an amino acid substitution affecting CDE6 protein function.
- CDE6 is a potential chloroplast ribosome recycle factor linked to high temperature sensitivity in rice.

## Abstract

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.