An Exon Skipping in CRS1 Is Associated with Perturbed Chloroplast Development in Maize.

Chloroplasts of higher plants are semi-autonomous organelles that perform photosynthesis and produce hormones and metabolites. They play crucial roles in plant growth and development. Although many seedling-lethal nuclear genes or regulators required for chloroplast development have been characterized, the understanding of chloroplast development is still limited. Using a genetic screen, we isolated a mutant named ell1, with etiolated leaves and a seedling-lethal phenotype. Analysis by BN-PAGE and transmission electron microscopy revealed drastic morphological defects of chloroplasts in ell1 mutants. Genetic mapping of the mutant gene revealed a single mutation (G-to-A) at the 5' splice site of intron 5 in CRS1, resulting in an exon skipping in CRS1, indicating that this mutation in CRS1 is responsible for the observed phenotype, which was further confirmed by genetic analysis. The incorrectly spliced CRS1 failed to mediate the splicing of atpF intron. Moreover, the quantitative analysis suggested that ZmCRS1 may participate in chloroplast transcription to regulate the development of chloroplast. Taken together, these findings improve our understanding of the ZmCRS1 protein and shed new light on the regulation of chloroplast development in maize.