Abstract
Regulatory mechanisms of stress responses in rice largely remain unclear. Using rice microarray, we identified many abiotic stress-responsive genes. Among them, a gene for a bHLH transcription factor down-regulated by drought stress has been studied. The bHLH protein showed a high sequence homology with Arabidopsis PIF1, driving us to name the transcription factor OsPIF1. Transgenic rice plants overexpressing OsPIF1 and dominant loss-of-function rice mutants with the chimera repressor changed internode elongation, suggesting that OsPIF1 functions as an important growth regulatory factor in response to drought stress in rice. Here, we clarified that OsPIF1 is highly expressed in a node using promoter-GUS analysis. We also found a candidate of target genes of OsPIF1 using microarray analysis. The candidate gene encodes an ethylene biosynthesis enzyme. The gene expression was strongly detected in the node and reduced by drought stress. Currently, we are trying to identify target genes of OsPIF1.
