Molecular plant 2016
The RNA editing factor WSP1 is essential for chloroplast development in rice.
Although the RNA editing factors (MORFs) in the plastids of Arabidopsis thaliana have been extensively studied, the molecular details of how MORFs affect plant development in other species, particularly in rice, have not been clarified. Here, we describe wsp1, a rice white stripe leaf/panicle mutant. Notably, immature panicles of wsp1 exhibit a white phenotype at the heading stage. Transmission electron microscopy and chlorophyll content measurements revealed a chloroplast developmental defect and a reduced and low rate of chlorophyll accumulation in wsp1. Positional cloning of WSP1 revealed a point mutation in LOC_Os04g51280, which shares high sequence homology with multiple organellar RNA editing factor (MORF) proteins. Complementation experiments demonstrated that WSP1 was responsible for the variegated phenotypes of wsp1. Sub-cellular localization studies showed that WSP1 is localized to chloroplasts. Furthermore, we found that the mutation in wsp1 affected multiple organellar RNA factor editing. Owing to plastid RNA factor editing defect, chloroplast ribosome biogenesis and ndhA splicing were also impaired in wsp1. The ribosome biogenesis defect and plastid-encoded RNA polymerase complex activity impairment in wsp1 potentially account for the stripe leaf in the seedling and white panicle in the heading stage. Together, this is the first study to demonstrate the importance of a rice WSP1 protein in chloroplast development and to broaden our knowledge about MORF family members (WSP1) in rice.