The rice white green leaf 2 gene causes defects in chloroplast development and affects the plastid ribosomal protein...

Plastid ribosomal proteins (PRPs) play important roles in the translation of key proteins involved in chloroplast development and photosynthesis. PRPs have been widely studied in many plant species; however, few studies have investigated their roles in rice.

In the present study, we used ethyl methane sulfonate mutagenesis and obtained a novel rice mutant called white green leaf 2 (wgl2). The wgl2 mutants exhibited an albino phenotype from germination through the three-leaf stage, and then gradually transitioned to green through the later developmental stages. Consistent with this albino phenotype, wgl2 mutants had abnormal chloroplasts and lower levels of photosynthetic pigments. Map-based cloning and DNA sequencing analyses of wgl2 revealed a single-nucleotide substitution (G to T) in the first exon of LOC_Os03g55930, which resulted in a substitution of glycine 92 to valine (G92 V). WGL2 encodes a conserved ribosomal protein, which localizes to the chloroplast. Complementation and targeted deletion experiments confirmed that the point mutation in WGL2 is responsible for the wgl2 mutant phenotype. WGL2 is preferentially expressed in the leaf, and mutating WGL2 led to obvious changes in the expression of genes related to chlorophyll biosynthesis, photosynthesis, chloroplast development, and ribosome development compared with wild-type.

WGL2 encodes a conserved ribosomal protein, which localizes to the chloroplast. WGL2 is essential for early chloroplast development in rice. These results facilitate research that will further uncover the molecular mechanism of chloroplast development.