Mutation of the ALBOSTRIANS Ohnologous Gene HvCMF3 Impairs Chloroplast Development and Thylakoid Architecture in Barley due to Reduced Plastid Translation

Gene pairs resulting from whole genome duplication (WGD), so-called ohnologous genes, are retained only if at least one gene of the pair undergoes neo- or subfunctionalization. Sequence-based phylogenetic analyses of the ohnologous genes () and (/) of barley () revealed that they belong to a newly identified subfamily of genes encoding CCT domain proteins with putative N-terminal chloroplast transit peptides. Recently, we showed that HvCMF7 is needed for chloroplast ribosome biogenesis. Here we demonstrate that mutations in lead to seedlings delayed in development. They exhibit a phenotype and successively develop pale green leaves. Compared to the wild type, plastids of the mutant seedlings show decreased PSII efficiency and lower amounts of ribosomal RNAs; they contain less thylakoids and grana with a higher number of more loosely stacked thylakoid membranes. Site-directed mutagenesis of identified a previously unknown functional region, which is highly conserved within this subfamily of CCT domain containing proteins. HvCMF3:GFP fusion constructs localized to plastids. double mutants indicated epistatic activity of over The chloroplast ribosome deficiency is discussed as the primary defect of the mutants. Our data suggests that HvCMF3 and HvCMF7 have similar but not identical functions.