Interaction of BPC1 and ALDH2 Affects Natural De-Astringency in Chinese PCNA Persimmon (Diospyros kaki)

Pollination-constant non-astringent (PCNA) persimmons have significant commercial value due to their natural de-astringency trait. The Chinese PCNA (C-PCNA) type is particularly valuable for genetic improvement because this trait is controlled by dominant genes. However, the regulatory mechanism underlying this trait remains unclear. Our previous research identified ALDH2 (acetaldehyde dehydrogenase 2, a key gene downstream of acetaldehyde metabolism) as being negatively correlated with natural de-astringency in C-PCNA persimmon, and revealed its interaction with DkBPC1, a transcription factor from the BBR/BPC (BARLEY B RECOMBINANT/BASIC PENTA CYSTEINE, abbreviated as the BPC protein family) family whose function had not been experimentally validated. The full-length cDNA of DkBPC1 was isolated from ‘Luotian Tianshi’ (C-PCNA type). A dual-luciferase assay demonstrated that DkBPC1 significantly enhances the promoter activity of DkALDH2b. Subcellular localization conducted in tobacco confirmed that DkBPC1 is localized in the nucleus. Transient overexpression of DkBPC1 in C-PCNA leaves and fruit discs resulted in a significant increase in soluble tannin content, a significant decrease in insoluble tannin content, and a notable upregulation of DkALDH2b gene expression. Conversely, transient knockdown of DkBPC1 expression in C-PCNA leaves led to a dramatic drop in soluble tannin content and a significant increase in insoluble tannin content. These results indicate that BPC1 can increase the conversion of soluble tannins to insoluble tannins by downregulating the expression of the DkALDH2 gene, thereby promoting natural de-astringency in C-PCNA persimmon.