Characterization and Fine Mapping of a Yellow-Virescent Gene Regulating Chlorophyll Biosynthesis and Early Stage Chloroplast Development in .

Chlorophyll biosynthesis and chloroplast development are crucial to photosynthesis and plant growth, but their regulatory mechanism remains elusive in many crop species. We isolated a yellow-virescent leaf () mutant, which exhibited yellow-younger-leaf and virescent-older-leaf with decreased chlorophyll accumulation and delayed chloroplast development. We mapped locus to a 70-kb interval between molecular markers yvl-O10 and InDel-O6 on chromosome A03 in BCF population using whole genome re-sequencing and bulked segregant analysis. The mutant had a 'C' to 'T' substitution in the coding sequence of , which encodes putative H subunit of Mg-protoporphyrin IX chelatase (CHLH). The mutation resulted in an imperfect protein structure and reduced activity of CHLH. It also hampered the plastid encoded RNA polymerase which transcribes regulatory genes of photosystem II and I. Consequently, the chlorophyll a/b and carotenoid contents were reduced and the chloroplast ultrastructure was degraded in mutant. These results explain that a single nucleotide mutation in impairs PEP activity to disrupt chloroplast development and chlorophyll biosynthesis in .