A sucrose transporter from Gongronella butleri w5 mediates plant-fungus-bacteria interaction

Beneficial fungi in the plant rhizosphere connect plants and soil bacteria by releasing carbon sources as a bridge. Sucrose, a direct product of plant photosynthesis, plays a crucial role in this process. Here, we report that the sucrose transporter (SUT) protein GspSUT1 worked as a key regulator in the plant-beneficial fungus Gongronella butleri w5 (w5) and promoted plant growth by modulating carbon allocation during plant-fungus-bacteria interactions. The GspSUT1 expression was upregulated during the w5-plant interaction, accompanied by a decrease in sucrose in the root of Actinidia chinensis var. Chinensis "Hongyang." Knocking down the expression level of GspSUT1 through host-induced gene silencing (HIGS) led to the accumulation of sucrose in the plant root and a reduction in the release of monosaccharides into the environment, which in turn decreased the abundance of soil nitrogen-fixing bacteria and lowered the available nitrogen content in the soil, thereby weakening the ability of w5 to promote plant growth. Our research suggested that GspSUT1 from w5 played a crucial role in promoting plant growth and proved that the SUTs in beneficial fungi can influence soil microbial composition by regulating carbon allocation during plant-fungus-bacteria interactions, thereby improving soil nutrient availability and promoting plant growth.