Two novel anoxia-induced ethylene response factors that interact with promoters of deastringency-related genes from persimmon.

A hypoxic environment is generally undesirable for most plants and stimulates anaerobic metabolism. It is a beneficial treatment, however, for the removal of astringency from persimmon to improve the fruit quality after harvest. High soluble tannins (SCTs) content is one of most important causes of astringency. High CO2 (95%) treatment effectively reduced SCTs in both "Mopan" and "Gongcheng-shuishi" persimmon fruit by causing increases in acetaldehyde. Using RNA-seq and realtime PCR, twelve ethylene response factor genes (DkERF11-22) were isolated and characterized, to determine those responsive to high CO2 treatment. Only two genes, DkERF19 and DkERF22, showed trans-activation effects on the promoters of deastringency-related genes pyruvate decarboxylase genes (DkPDC2 and DkPDC3) and the transcript levels of these genes was enhanced by hypoxia. Moreover, DkERF19 and the previously isolated DkERF9 had additive effects on activating the DkPDC2 promoter. Taken together, these results provide further evidence that transcriptome changes in the level of DkERF mRNAs regulate deastringency-related genes and their role in the mechanism of persimmon fruit deastringency is discussed.