Molecular cloning and expression analysis of hexokinase genes in peach fruit under postharvest disease stress

Abstract

Hexokinase (HXK) is a bifunctional enzyme and plays a critical role in plants growth and stress response. HXK is encoded by a multi-gene family in a wide range of plants. However, information of HXK family members in peach and their expression pattern under disease stress remains unclear. In the present study, 5 PpHXK genes in peach fruit, including PpHXK1-3 and PpHKL1-2, were identified and isolated, and clustered into 4 groups by phylogenetic tree analysis. Furthermore, we investigated HXK activity, transcript levels of the 5 PpHXK genes and sugar content in peach fruit under Monilinia fructicola infection in 2018 and 2019. The results in both 2018 and 2019 showed that M. fructicola infection increased HXK activity and PpHXK2 gene expression, and accelerated sucrose decomposition. HXK activity showed significantly positive correlation with PpHXK2 expression and negative correlation with sucrose content. PpHXK2 was localized in the cytoplasm by subcellular localization, and contained 3 W-box cis-acting elements in the promoter, indicating that PpHXK2 may function as a sugar sensor and regulate sugar signaling and metabolism in defense response against pathogen infection. Thus, PpHXK2 in peach fruit is capable of responding to postharvest disease stress, and the involved mechanism needs to be further studied.