Sucrose transport gene FaSWEET9a regulated by FaDOF2 transcription factor promotes sucrose accumulation in strawberry.

Abstract

Key message: FaSWEET9a, an important sucrose transport gene regulated by transcription factor FaDOF2, regulates the accumulation of sucrose in strawberry fruits and affects the growth of strawberry plants.. This study identified and characterized 25 members of the SWEET gene family in the genome of cultivated strawberry (Fragaria × ananassa cv. 'Yanli'), focusing on their potential roles in fruit development. Notably, FaSWEET9a, a specific member of the SWEET family, was found to be uniquely expressed in 'Yanli' fruit. Functional analysis via heterologous expression in Saccharomyces cerevisiae confirmed that FaSWEET9a acts as a sucrose transporter. To further investigate its role, we generated FaSWEET9a overexpression lines and demonstrated that FaSWEET9a not only enhances sucrose accumulation in strawberry fruits but also influences plant growth and development. We identified FaDOF2 that could bind to the promoter of FaSWEET9a and enhance its transcription by conducting yeast one-hybrid assays, electrophoretic mobility shift assays, β-glucuronidase assays, and luciferase reporter gene assays. Moreover, transient transformation experiments revealed that FaDOF2 could elevate sucrose content in strawberry fruits by regulating FaSWEET9a. This research brings new viewpoints on the molecular mechanisms that govern sucrose regulation in strawberry fruits, spotlighting the functional significance of the FaSWEET9a-FaDOF2 regulatory module in the aspects of fruit quality and development.