Isolation and characterization of genes encoding GRF transcription factors and GIF transcriptional coactivators in Maize (Zea mays L.)

It has been a long-held view that regulation of gene expression in eukaryotes occurs predominantly at the transcriptional level. GRF (Growth-regulating factor) and GIF (GRF-interacting factor) proteins are putative novel transcriptional regulators and coactivators which form protein complexes and are involved in regulating the growth and development of certain tissues and/or organs in plants. In this study, 14 homologs of ZmGRF genes and 3 homologs of ZmGIF genes from maize (Zea mays L.) were identified and characterized. Fourteen GRF proteins were divided into three subfamilies. ZmGRF genes of C subfamily were mainly expressed in immature ears. Furthermore, overexpression of both ZmGRF11-ZmGIF2 and ZmGRF2-ZmGIF3 resulted in delayed bolting but accelerating the growth of inflorescence stem when compared to wild-type Arabidopsis thaliana. As a result, we postulated that these four genes which expressed preferentially in immature ear tissues in maize might play important roles in the growth and development of ears and might contribute to improving corn yields.