DkMYB6 is involved in persimmon fruit deastringency, via transcriptional activation on both DkPDC and DkERF

• 95% CO2 treatment effectively accelerated ‘Mopan’ persimmon postharvest deastringency.
• DkMYB genes were isolated and induced in response to 95% CO2 treatment.
• DkMYB6 trans-activated deastringency related DkPDC2/3 and DkERF9/19 promoters.

Postharvest deastringency is important for persimmon fruit, since most cultivars are of the astringent type. In the present research, astringency as indicated by the decrease in soluble tannin content, was removed from ‘Mopan’ persimmon by placing them in an atmosphere of 95% CO2. In contrast to the decrease in soluble tannin, increases in concentrations of acetaldehyde and ethanol were transiently triggered by CO2 treatment. Four DkMYB genes, DkMYB5–8, belonging to the R2R3 MYB family, were isolated. mRNA accumulation studies indicated that DkMYB5–8 were up-regulated by CO2 treatment, and that expression was positively correlated with persimmon fruit astringency removal. However, using a dual-luciferase assay, only one of these four DkMYB genes, DkMYB6, showed the ability to trans-activate the promoters of the previously identified persimmon fruit deastringency-related genes DkPDC2 and DkPDC3. Furthermore, DkMYB6 were also observed to be an activator of the previously characterized deastringency regulators, DkERF9 and DkERF19. Thus, DkMYB6 is a putative transcriptional activator, induced by high CO2, which is involved in persimmon fruit deastringency, by operating on both DkPDC structural genes and DkERF transcription factors.