As one of the most severe stress conditions, drought strongly affects the plant growth and productivity. OsPIL1, a gene encoding a rice Phytochrome Interacting Factor (PIF)-Like transcription factor, was found to be down-regulated under drought stress condition. OsPIL1 shows a diurnal expression pattern and known to be involved in regulation of plant height. However, the mechanisms of down-regulation of OsPIL1 expression under stress conditions are remained unclear. In this study, the expression of PIF4 and PIF5, the most homologous genes of OsPIL1 in Arabidopsis, was analyzed and the expression of these genes were found to be oscillated in circadian manner and down-regulated in response to drought and low temperature similar to that of OsPIL1. To identify the regions involved in the responses to drought, low temperature and diurnal cycle, the promoter analysis of PIF4 was performed using transgenic Arabidopsis. Further promoter analysis is ongoing to specify regulatory regions in more detail.

As one of the most severe stress conditions, drought strongly affects the plant growth and productivity. OsPIL1, a gene encoding a rice Phytochrome Interacting Factor (PIF)-Like transcription factor, was found to be down-regulated under drought stress condition. OsPIL1 shows a diurnal expression pattern and known to be involved in regulation of plant height. However, the mechanisms of down-regulation of OsPIL1 expression under stress conditions are remained unclear. In this study, the expression of PIF4 and PIF5, the most homologous genes of OsPIL1 in Arabidopsis, was analyzed and the expression of these genes were found to be oscillated in circadian manner and down-regulated in response to drought and low temperature similar to that of OsPIL1. To identify the regions involved in the responses to drought, low temperature and diurnal cycle, the promoter analysis of PIF4 was performed using transgenic Arabidopsis. Further promoter analysis is ongoing to specify regulatory regions in more detail.