Monosaccharide transporters in plants: from molecular mechanisms to agricultural potential applications

• MSTs are pivotal for photosynthate unloading in sink tissues. • MSTs directly govern key yield-related plant growth and developmental processes. • MSTs confer plant resistance to both biotic and abiotic stresses. • The activity of MSTs is precisely modulated by post-translational modifications. • We evaluate the untapped potential of MSTs for targeted crop yield enhancement. Sugars produced by photosynthesis provide energy for plant cells and serve as carbon skeletons for synthesizing organic compounds. Sucrose, the main transported form of photoassimilates, is translocated via the phloem from source to sink. Before entering sink cells, sucrose is often hydrolyzed into glucose and fructose, which are then imported into sink cells primarily by monosaccharide transporters (MSTs) to support metabolic processes. Although the functions of plant MSTs have been extensively characterized, a system-level understanding of their functional specificity and regulatory networks-particularly their contributions to agricultural productivity-remains lacking. This review focuses on recent advances in understanding the roles of MSTs in regulating plant growth, development, and responses to biotic and abiotic stresses, and also discusses their post-translational regulation. We highlight the current research gaps concerning MSTs and propose the targeted engineering of MST networks as a promising strategy for developing high-yielding and stress-tolerant crop varieties.