Ethylene Promotes Submergence-Induced Expression of OsABA8ox1, A Gene that Encodes ABA 8'-Hydroxylase in Rice

Abstract

A rapid decrease of the plant hormone ABA under submergence is thought be a prerequisite for the enhanced elongation of submerged shoots of rice (Oryza sativa L.). Here, we report that the level of phaseic acid (PA), a catabolite of ABA, increased with decreasing ABA level after submergence. The oxidation of ABA to PA is catalyzed by ABA 8'-hydroxylase, which is possibly encoded by three genes (OsABA8ox1-3) in rice. The mRNA level of OsABA8ox1 increased dramatically within 1 h after submergence. Treatment of aerobic seedlings with ethylene and ACC rapidly induced the expression of OsABA8ox1. Moreover, pretreatment with 1-MCP partially suppressed induction of OsABA8ox1 expression after submergence. The ABA level was found to be negatively correlated with OsABA8ox1 expression after ACC or 1-MCP treatment. Together, these results indicate that the rapid decrease in ABA levels in submerged rice shoots is triggered in part by ethylene-induced expression of OsABA8ox1.