Editing of Chloroplast by PPR Editing Factor EMB2261 Is Essential for Development.

RNA editing in plastids is known to be required for embryogenesis, but no single editing event had been shown to be essential. We show that the mutation is lethal through a failure to express an editing factor that specifically recognizes the site. EMB2261 was predicted to bind the -element upstream of the site and genetic complementation with promoters of different strength followed by RNA-seq analysis was conducted to test the correlation between editing and expression. is the only editing event in chloroplasts that correlates with expression. Sequence divergence between the -element and the EMB2261 protein sequence in plants where editing is not required adds support to the association between them. We conclude that EMB2261 is the specificity factor for editing. This editing event converts P51 in Rps14 to L51, which is conserved among species lacking RNA editing, implying the importance of the editing event to Rps14 function. Rps14 is an essential ribosomal subunit for plastid translation, which, in turn, is essential for embryogenesis.