Abstract
Regulatory mechanisms of stress responses in rice largely remain unclear, compared to those in Arabidopsis. Using rice microarray, we identified many abiotic stress-responsive genes. Among them, a gene for a bHLH transcription factor repressed expression under drought stress condition. The bHLH protein showed a high sequence homology with Arabidopsis PIF3-like 5 (PIL5), and possessed a PIL motif at N-terminus, driving us to name the transcription factor OsPIL5.
To identify the function of OsPIL5, we generated transgenic Arabidopsis plants overexpressing OsPIL5 and observed their phenotypes. The transgenic plants showed growth promotion and decreased tolerance to drought stress. In contrast, a dominant loss-of-function Arabidopsis mutant of OsPIL5 with a repression domain exhibited growth retardation and increased tolerance to drought stress. It is possible that OsPIL5 functions as an important growth regulatory factor in response to drought stress in rice. Currently, using transgenic rice plants, we are analyzing function of OsPIL5.
