The changes in sugar content and the selection of key genes at different developmental stages of 'Katy' and 'Kuijin' apricots.

'Katy' and 'Kuijin' apricots are the main cultivated varieties in Shandong province. The flavor of the fruit is mainly determined by sugars and acids, with soluble sugar components serving as important nutritional elements in fruits as well as crucial indicators of fruit sweetness and flavor quality. However, little is known about the changes in soluble sugar content, especially sucrose content, and the sucrose metabolism mechanism during the entire fruit growth and development process of 'Katy' and 'Kuijin' apricots. In this study, we first detected the changes in sucrose, fructose, and glucose content at nine fruit development stages of 'Katy' and 'Kuijin' apricots, and found that the stage of rapid accumulation of sucrose and fructose was from 56 days after full bloom (DAF) to 63 DAF. Therefore, we identified the key gene PaSS1 of sucrose synthase through transcriptome data screening, and further analyzed the function of the PaSS1 gene in fruit sucrose metabolism process using virus-induced gene silencing (VIGS) technology. Silencing the PaSS1 gene reduced the breakdown activity of sucrose synthase, increasing sucrose content while decreasing glucose and fructose content, delaying fruit coloring and ripening, indicating that the PaSS1 gene may regulate the ripening of apricot fruits. This study provides a theoretical basis for further research on the molecular mechanism of the PaSS1 gene in apricot fruit ripening process.