Dramatic increase of Endochitinase gene expression during persimmon maturation and its potential role in fruit ripening

Abstract

Persimmon (Diospyros kaki), an economically significant fruit crop, undergoes complex physiological and biochemical changes during fruit development. This study focused on RNA-sequencing analysis across different stages of persimmon fruit development, specifically targeting the expression patterns of an endochitinase gene identified on chromosome 4, which had not been previously annotated in the D. kaki genome. The endochitinase designated as DKAch04aextra, showed a significant increase in expression, accounting for similar to 10% of the raw read counts, coinciding with the onset of fruit ripening in three pollination variant astringency type persimmon cultivars. Interestingly, this pattern of expression was also observed in pollination constant non-astringency type persimmons, indicating a potential universal role in persimmon fruit ripening regardless of astringency characteristics. Comparative analysis with previously assembled persimmon genomes highlighted the need for further annotation within the D. kaki genome to identify unannotated endochitinase potentially relevant to fruit ripening. While the data do not allow definitive conclusions about a regulatory function, the strong expression pattern of DKAch04aextra during ripening stages suggests its putative involvement in physiological changes such as cell wall modification. These findings provide a basis for considering DKAch04aextra as a candidate gene associated with fruit ripening and may inform future studies aimed at improving fruit quality through genetic and postharvest strategies.