WSL9Encodes an HNH Endonuclease Domain-Containing Protein that Is Essential for Early Chloroplast Development in Rice

Background The plant chloroplast is essential for photosynthesis and other cellular processes, but an understanding of the biological mechanisms of plant chloroplast development are incomplete. Results A new temperature-sensitivewhite stripe leaf 9(wsl9)rice mutant is described. The mutant develops white stripes during early leaf development, but becomes green after the three-leaf stage under field conditions. Thewsl9mutant was albinic when grown at low temperature. Gene mapping of theWSL9locus, together with complementation tests indicated thatWSL9encodes a novel protein with an HNH domain.WSL9was expressed in various tissues. Under low temperature, thewsl9mutation caused defects in splicing ofrpl2, but increased the editing efficiency ofrpoB.Expression levels of plastid genome-encoded genes, which are transcribed by plastid-coded RNA polymerase (PEP), chloroplast development genes and photosynthesis-related genes were altered in thewsl9mutant. Conclusion WSL9encodes an HNH endonuclease domain-containing protein that is essential for early chloroplast development. Our study provides opportunities for further research on regulatory mechanisms of chloroplast development in rice.