DkNAC7, a novel high-CO2/hypoxia-induced NAC transcription factor, regulates persimmon fruit de-astringency

Artificial high-CO2 atmosphere (AHCA, 95% CO2 and 1% O2) has been widely applied as a postharvest de-astringency treatment for persimmon fruit. AHCA increases expression of transcription factors, including ethylene response factors (DkERF), that target de-astringency genes. Here, the promoter of DkERF9, a previously characterized AHCA-inducible and de-astringency regulator, was utilized to screen a cDNA library by yeast one hybrid assay. A novel NAC transcription factor, named DkNAC7, was identified. Dual-luciferase assay indicated that DkNAC7 could not only trans-activate the promoter of DkERF9, but also activated the previously identified deastringency-related gene DkPDC2. Real-time PCR analysis showed that DkNAC7 was up-regulated by AHCA treatment, in concert with the removal of astringency from persimmon fruit and subcellular localization showed DkNAC7 was located in the nucleus. Thus, these results indicate that DkNAC7 is a putative transcriptional activator involved in regulating persimmon fruit deastringency by trans-activition on both DkERF9 and DkPDC2, which encodes pyruvate decarboxylase.