SUBMERGENCE ENHANCES EXPRESSION OF A GENE ENCODING 1-AMINOCYCLOPROPANE-1-CARBOXYLATE OXIDASE IN DEEP-WATER RICE

Partial submergence greatly stimulates internodal growth in deepwater rice (Oryza sativa L.). Previous work has shown that the effect of sub mergence is, at least in part, mediated by ethylene, which accumulates in the air spaces of submerged internodes. To investigate the express ion of the genes encoding ethylene biosynthetic enzymes during acceler ated growth of deepwater rice, we cloned a 1-amino-cyclopropane-1-carb oxylate (ACC) oxidase cDNA (OS-ACO1) from internodes of submerged plan ts and measured the activity of the enzyme in tissue extracts with an improved assay. We found an increase in ACC oxidase mRNA levels and en zyme activity after 4 to 24 h of submergence. Thus, it is likely that ethylene biosynthesis in internodes of deepwater rice is controlled, a t least in part, at the level of ACC oxidase.