A rice cytochrome P450 OsCYP84A that may interact with the UV tolerance pathway.

Cytochrome P450s are widespread in the plant kingdom. The functions of plant P450s are dispersed through many aspects of plant metabolisms, which are involved in the biosynthesis of defense compounds and protectants against ultraviolet rays, as well as metabolic pathways for the biosynthesis and/or degradation of fatty acids, hormones, and signaling molecules. We found a gene for rice P450, OsCYP84A, which was classified into CYP84A in the CYP71 clan. Reverse transcription-polymerase chain reaction (RT-PCR) analysis indicated that this gene was ubiquitously expressed without any temporal and spatial specificity under normal growth conditions, but its expression was inducibly and significantly increased by ultraviolet (UV)-B and UV-C irradiation. Rice transformants in which OsCYP84A expression was suppressed by the antisense gene showed apparent growth retardation with obvious symptoms of damage on the plant bodies under UV-B irradiation, although no phenotypic alteration occurred under normal growth conditions. These results suggest the existence of a novel UV-tolerance system involving OsCYP84A.