Cold-Responsive Regulation of a Flower-Preferential Class III Peroxidase Gene, OsPOX1, in Rice (Oryza sativa L.)

A full-length cDNA corresponding to ddOs319, previously isolated as a cold-responsive gene in the flowers by mRNA differential display (Plant Cell Rep 26:1097-1110, 2007), was obtained from the cold-treated flowers by reverse transcription and nested PCR. The cDNA encodes a putative class III peroxidase of 335 amino acids with 77-98% identity with rice peroxidases and named OsPOX1. To understand the regulation of OsPOX1 expression, a 1.8 kb promoter region of OsPOX1 was isolated and fused to beta-glucuronidase (GUS) reporter gene. Transgenic rice plants expressing P (OsPOX1) -GUS showed minimal GUS activity in both shoots and roots at the vegetative stage. In the flowers at early young microspore stage, GUS activity was detected in the veins and anthers. Interestingly, at the later vacuolated pollen stage, the GUS activity was highly induced by cold stress, suggesting that OsPOX1 is a flower-preferential cold-responsive gene in rice.