Interaction of brassinosteroid functions andsucrose transporter SlSUT2 regulate theformation of arbuscular mycorrhiza

摘要

Transgenic tomato plants with reduced expression of the sucrose transporter SlSUT2 showed higher efficiency ofmycorrhization suggesting a sucrose retrieval function of SlSUT2 from the peri-arbuscular space back into the cellcytoplasm plant cytoplasm thereby limiting mycorrhiza fungal development. Sucrose uptake in colonized root cellsrequires efficient plasma membrane-targeting of SlSUT2 which is often retained intracellularly in vacuolar vesicles.Protein-protein interaction studies suggested a linkbetween SISUT2 function and components of brassinosteroidbiosynthesis and signaling. Indeed, the tomato DWARF mutantdxdefective in BR synthesis1showed significantlyreduced mycorrhization parameters.2The question has been raised whether the impact of brassinosteroids onmycorrhization is a general phenomenon. Here, we include a rice mutant defective in DIM1/DWARF1 involved in BRbiosynthesis to investigate the effects on mycorrhization. A model is presented where brassinolides are able to impactmycorrhization by activating SUT2 internalization and inhibiting its role in sucrose retrieval.