Abstract
GAMYB was identified as a positive transcriptional regulator of gibberellin (GA)-responsive genes in barley aleurone. Recently, we showed that the rice GAMYB, OsGAMYB, is also essential for the anther development by using gamyb.
We observed abnormal anthers of gamyb and GA-related mutants, and found that all these mutants showed similar defects in tapetum and exine development. A microarray analysis suggested that the expression of almost GA-responsive genes in anthers is under the control of OsGAMYB. Almost GA-responsive genes contain putative GAMYB binding motifs in promoter regions. We focused on two GA-responsive genes, involved in exine formation, to examine that OsGAMYB really targets GA-responsive genes. OsGAMYB specifically interacted with these putative GAMYB binding motifs in vitro. Furthermore, the mutations to these motifs showed the reduced GUS expression in promoter-GUS lines. Based on these results, we conclude that GA controls these genes expression through the direct regulation by OsGAMYB in anther development.
