Cloning And Characterization Of A Novel Water-stress-suppressed Gene OsARD In Rice

The aci-reductone dioxygenase (ARD) family is evolutionarily conserved from bacteria to plants and animals. The ARD is involved in the methionine salvage pathway. A . water-stress-suppressed gene, OsARD encoding an aci-reductone-dioxygenase-like protein, was identified from rice (Oryza sativa L.). Northern blot and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed that the OsARD expression is regulated by abiotic stresses and phytohormones. OsARD was mainly expressed in roots under flooding condition, while suppressed by water deficit, ABA, high salinity and low tempetature, but induced by ethylene and gibberellin acid (GA). The transgenic plants with reduction of OsARD expression showed that the genes for S-adenosylmethionine (SAM) synthase and 1-aminocyclopropane-l-carboxylic acid (ACC) synthase arc negatively regulated by OsARD. The expression of the two genes, ETR2 and E1N3, was increased in these RNAi transgenic, plants, whereas the expression of ERF3 was suppressed. These results suggest that OsARD may play a role in the metabolism of methionine and ethylene in response to abiotic stresses.