Barley young leaf chlorina, a putative pentatricopeptide repeat gene, is essential for chloroplast development in young leaves

Abstract

A spontaneous barley mutant, young leaf chlorina (ylc), was identified in this study. Young leaves of ylc exhibited a yellow base and green tip, with reduced chlorophyll content, and altered chlorophyll fluorescence pattern, and underdeveloped grana in chloroplasts. The color of mutant leaves gradually transitioned to pale green and then became green in mature leaves. The ylc phenotype was found to be controlled by a recessive locus mapped to a 2.4 Mb interval on chromosome 7HS using bulked-segregant analysis with deep sequencing and further fine mapped to a 410 kb interval using polymorphic markers. The YLC locus co-segregated with a molecular marker that led to identification of HORVU7Hr1G011570 as the most likely candidate gene. As compared to the barley reference genome, the candidate ylc allele contained nucleotide changes that would lead to functional alterations of its protein product. The candidate YLC gene encodes a DYW-type pentatricopeptide repeat (PPR) protein, implicated in RNA cleavage and RNA editing in chloroplasts. Chlorophyll fluorescence analysis suggests that the PPR protein may regulate chloroplast development through the function of NAD(P)H dehydrogenase (NDH) complex and plays a pivotal role in mediating electron flow in thylakoid membranes during leaf growth in barley.