A transcription factor network responsive to high CO(2)/hypoxia is involved in deastringency in persimmon fruit

Plant responses to anaerobic environments are regulated by ethylene-response factors (ERFs) in both vegetative and productive organs, but the roles of other transcription factors (TFs) in hypoxia responses are poorly understood. In this study, eight TFs (DkbHLH1, DkMYB9/10/11, DkRH2-1, DkGT3-1, DkAN1-1, DkHSF1) were shown to be strongly up-regulated by an artificial high-CO(2) atmosphere (1% O(2) and 95% CO(2)). Dual-luciferase assays indicated that some TFs were activators of previously characterized DkERFs, including DkMYB10 for the DkERF9 promoter, DkERF18/19 and DkMYB6 for the DkERF19 promoter, and DkERF21/22 for the DkERF10 promoter. Yeast one-hybrid and cis-element mutagenesis confirmed these physical interactions with one exception. The potential roles of these TFs in persimmon fruit deastringency were analysed by investigating their transient over-expression (TOX) in persimmon fruit discs, which indicated that DkMYB6(TOX), DkMYB10(TOX), DkERF18(TOX), and DkERF19(TOX) were all effective in causing insolubilization of tannins, concomitantly with the up-regulation of the corresponding genes. These results indicated that multiple TFs of different classes are responsive to high-CO(2)/hypoxia in fruit tissues, and that a TF–TF regulatory cascade is involved in the hypoxia responses involving the Group VII DkERF10, and DkERFs and DkMYBs.