Functional analyses of OsGLK1 and OsGLK2, GARP-type transcription factors, regulating chloroplast differentiation in rice

Abstract

Plants convert light energy to chemical energy by performing photosynthesis in chloroplasts. Chloroplasts are differentiated from proplastids during plant development, but how the differentiation is achieved is only partially understood. Recently, we obtained a clue to elucidate the molecular mechanism in rice. When we ectopically overexpressed OsGLK1 encoding a GARP-type transcriptional regulator in rice, the OsGLK1-overexpressing calli exhibited green color on a 2,4-D-containing medium. The green calli accumulated transcripts for a set of genes involved in photosynthesis or other chloroplast functions. These results showed that OsGLK1 is a key factor regulating chloroplast development. Similarly, overexpression of OsGLK2, a homolog of OsGLK1, generated green calli, indicating not only OsGLK1 but OsGLK2 play crucial role(s) in chloroplast development. Further studies are in progress to characterize the common and different features between the two GLKs by analyzing their gene-expression patterns and candidate genes under the control of individual GLK proteins.