The roles of hexose in fruit set and characterization of HXKs in litchi

Litchi (Litchi chinensis Sonn.) is a popular evergreen fruit tree in the world’s tropical and subtropical regions. It is widely planted for its high economic value in southern China. The litchi industry is critical to farmer income and rural revitalization in South China. However, due to the severe fruit abscission and thus low fruit setting rate, large amounts of flower with no or few fruit set occur frequently in litchi production. This phenomenon severely impedes the litchi industry’s long-term development. In the present study, a much higher fruit retention rate, cultivar ‘Heiye’ (HY) contains significantly more hexoses such as galactose, fructose, and glucose than cultivar ‘Nuomici’ (NMC). Furthermore, exogenous D-glucose significantly reduces the fruit dropping rate, indicating that glucose plays an important role in litchi fruit abscission. Previous research has shown that litchi fruit sheds heavily in response to carbohydrate deficiency. Sugar, in addition to providing carbon skeletons and energy in plants, may play a role in the regulation of the entire life cycle as a sugar signal. In the current study, five potential glucose sensors, known as HXKs, were isolated and characterized.