Soluble sugars accumulation and related gene expression during fruit development in Cucurbita maxima Duchesne

Abstract

In this study, two pumpkin lines were used as experimental materials to study the accumulation of soluble sugars and the expression of related genes during the development of pumpkin fruits. There were differences in the soluble sugars contents and regulatory mechanisms between the two pumpkin lines. The glucose content of ‘312-1’ decreased rapidly in the early stage of fruit development, which may be due to the high expression of Sucrose invertase (INV) and Hexokinase (HK) at this stage. There were significant differences in sucrose contents between mature fruits of ‘312-1’ and ‘98-2’, and the high expression of Sucrose synthase (SUS) and Sucrose phosphate synthase (SPS) led to sucrose accumulation in these pumpkins. The relative expression of SPS in ‘312-1’ was higher than that in ‘98-2’, which led to more sucrose accumulation in the former. In contrast, the Fructokinase (FK), which is responsible for fructose metabolism, was differentially expressed at individual stages of fruit development. These results indicate that INV, SUS, SPS, HK and FK may play significant roles by contributing coordinately to sucrose biosynthesis during pumpkin fruit development. This study provides a deeper understanding of the molecular mechanism of sucrose biosynthesis and a basis for further studies on the improvement of fruit eating quality in pumpkin.