SCL, Encoding a Chloroplast Signal Recognition Particle Receptor, Affects Chlorophyll Synthesis and Chloroplast Development in Rice

Crop yield is largely determined by the solar energy utilization efficiency of photosynthesis; plants with long stay-green periods have greater total photosynthetic production levels and crop yields. Here, a novel seedling chlorosis and lethality (scl) mutant exhibiting a yellow leaf and seedling-lethal phenotype was identified in rice (Oryza sativa L.). The mutant had deformed chloroplasts and almost no protein complexes in thylakoid membranes. The expression levels of photosynthesis-associated genes were significantly down-regulated in scl compared with the wild-type (WT). Positive transgenic lines generated by Agrobacterium tumefaciens-mediated transformation of the scl mutant with a complementation vector harboring SCL cDNA exhibited the normal green leaf phenotype, whereas the scl seedling harboring the empty vector displayed the yellow leaf phenotype, indicating that SCL is LOC_Os01g72800. A fusion protein expressing SCL with green fluorescent protein revealed the fluorescence signal localized to chloroplasts. The expression patterns of chloroplast development and chlorophyll biosynthesis and degradation-related genes were disordered in scl mutant, possibly resulting in the yellow leaf phenotype. These results indicated that the SCL loss of function impaired chloroplast development, chlorophyll biosynthesis, and light-harvesting chlorophyll-binding protein transportation in rice.