Responses of Male and Female Cucumber Flowers to CsHXK2-Mediated Sugar Metabolism.

Plant hexokinase (HXK) is a key enzyme in carbohydrate metabolism that serves a dual function by catalyzing hexose phosphorylation and participating in sugar signaling. In this study, expression pattern analysis and reverse-genetic approaches were used to investigate the role of CsHXK2 in cucumber floral development. CsHXK2 was predominantly expressed in the stamens and nectary of male flowers and in the stigma, nectary, and ovary of female flowers. The CsHXK2 protein was localized to chloroplasts. Silencing CsHXK2 significantly increased glucose, fructose, and sucrose levels in the examined tissues of both male and female flowers. This increase was accompanied by reduced activities of HXK, PFK, AI, SS-I, and NI and enhanced activities of SPS and SS-II, with these changes being more pronounced in female flowers than in male flowers. Gene expression analysis further revealed that CsHXK2 silencing induced tissue-specific changes in the expression of sugar-metabolism-related genes in both male and female flowers. These results demonstrate that CsHXK2 contributes to the maintenance of sugar homeostasis in cucumber floral organs. Moreover, male and female floral organs exhibit distinct responses to HXK-mediated regulation of sugar metabolism, suggesting that CsHXK2 may influence cucumber flower development by modulating carbon allocation and sugar signaling.