Transcriptional Regulation of the Rice Phytase Gene OsPHY1 by Several Phytohormones and Osmotic Stresses Using Promoter-GUS Analysis

摘要

During germination, phytate, a major phosphate compound in seeds, is degraded into inorganic phosphorus (Pi) for differentiation of new tissues via catalysis. OsPHY1, a member of phytase genes in rice, has previously been found to show high expression levels in the endosperm and hypocotyl during germination and is involved in the degradation of seed phytate. In this study, we investigated the transcriptional mechanisms of OsPHY1 via OsPHY1 promoter-GUS analysis. The results of GUS histochemical staining and activities in tobaccos harboring OsPHY1-GUS reveal that the reporter gene is strongly expressed in the hypocotyl and responds to diverse stimuli cues initiated by phytohormones abscisic acid (ABA), gibberellin (GA(3)), and indole-3-acetic acid (IAA), as well as osmotic stresses of salt, drought, and cold. The results indicate that the cis-regulatory element CANBNNAPA regulates gene hypocotyl-predominant expression. ABRE and GAREAT are involved in gene responses to ABA and GA(3), respectively, and DRECRTCOREAT is involved in gene responses to stresses of salt, drought, and cold. In addition, the responses of OsPHY1 and part-osmotic stress-responsive genes to salt, drought, and cold mediated by DRECRTCOREAT are largely accomplished through the ABA-dependent pathway with the involvement of the ABA responsive cis-regulatory element ABRE. Our results reveal that the degradation of seed phytate during germination mediated by OsPHY1 is regulated in a fine-tune manner with the involvement of diverse cis-regulatory elements at the transcription level.