Rapid induction of a novel ACC synthase gene in deepwater rice seedlings upon complete submergence

Elongation growth is a typical feature of deepwater rice plants in response to submergence. The growth phenomenon is known to be induced by hypoxia, which results in the expression of genes implicated in ethylene biosynthesis. Ethylene is considered to trigger the growth response as it accumulates in the submerged tissues and submergence enhances the expression of 1-aminocyclopropane-1-carboxylate (ACC) synthase. However, ACC concentration in rice plants increases much faster after submergence than the activity of the ACC synthase genes studied previously. Here, we studied the expression characteristics of the fifth member of this gene family, OS-ACS5, and show that submergence induces the messenger concentration of this gene before the accumulation of ACC could be observed. OS-ACS5 may play a fundamental role in the growth-promoting increase in ethylene biosynthesis during the first hours of submergence in deepwater rice.