SUB1A-1 anchors a regulatory cascade for epigenetic and transcriptional controls of submergence tolerance in rice.

Most rice () cultivars cannot survive under prolonged submergence. However, some ssp. cultivars, such as FR13A, are highly tolerant owing to the () allele, which encodes a Group VII ethylene-responsive factor (ERFVII) protein; other submergence-intolerant cultivars contain a allele. The two alleles differ only by a single substitution at the 186 amino acid position from serine in SUB1A-1 to proline in SUB1A-2 resulting in only SUB1A-1 being able to be phosphorylated. Two other ERFVIIs, and , function downstream of SUB1A-1 to form a regulatory cascade in response to submergence stress. Here, we show that SUB1A-1, but not SUB1A-2, interacts with ADA2b of the ADA2b-GCN5 acetyltransferase complex, in which GCN5 functions as a histone acetyltransferase. Phosphorylation of SUB1A-1 at serine 186 enhances the interaction of SUB1A-1 with ADA2b. and expression was induced under submergence, suggesting that these two genes might play roles in response to submergence stress. In transient assays, binding of SUB1A-1 to the promoter and transcription were highly induced when SUB1A-1 was expressed together with the ADA2b-GCN5 acetyltransferase complex. Taken together, these results suggest that phospho-SUB1A-1 recruits the ADA2-GCN5 acetyltransferase complex to modify the chromatin structure of the promoter regions and activate gene expression, which in turn enhances rice submergence tolerance.