Soluble sugars are the key photo-assimilates in higher plants, playing critical roles in growth, development, and stress regulation. The transport of sugars in plants involves the coordinated action between several sugar transporter families, including the SUT, STP, pGlcT, VGT, TMT, INT, PLT, SFP, and SWEET families. Over recent decades, numerous studies have elucidated the molecular functions of major sugar transporters. Phylogenetic and evolutionary analyses support the conservation of substrate specificity and transport direction, at least to some extent. Structural analyses have provided key insights into the structural–function relationships of important transporters (e.g., OsSWEET2b and AtSTP10), which can be effectively leveraged for artificial intelligence (AI)-enabled protein structure prediction and rational design. Advances in omics technologies now enable low-cost, routine transcriptome profiling and cutting-edge techniques (e.g., single-cell multi-omics and spatiotemporal RNA-seq), providing unprecedented ways to understand how sugar transporters function coordinately at multiple levels. Here, we describe the classification of major sugar transporters in plants and summarize established functional knowledge. We emphasize that recent groundbreaking advances in AI-enabled protein analyses and multi-omics will revolutionize molecular physiology in crops. Specifically, the integration of functional knowledge, AI-based protein analyses, and multi-omics will help unravel the orchestration of different sugar transporters, thereby enhancing our understanding of how sugar transportation and source–sink interactions contribute to crop development, yield formation, and beyond, ultimately boosting carbohydrate transport- related crop improvement.

XYLEM CYSTEINE PROTEASE 1 (XCP1) is a cysteine protease that plays a critical role in xylem differentiation and tracheary element (TE) formation. Our previous study demonstrated that TE remodeling occurs at the graft union in the Arabidopsis thaliana (At)/Nicotiana benthamiana (Nb) interfamilial graft. Here, we identify that the AtXCP1 transcript is specifically localized in TEs at the graft interface of the incompatible At/Nb interfamilial grafts, and its expression is reduced in these incompatible grafts compared to the compatible grafts. Analysis of AtXCP1pro::GFP reporter lines revealed that AtXCP1 expression is rapidly induced by wounding at the graft interface in At/Nb interfamilial grafts during the early grafting stage. Notably, AtXCP1 expression was significantly stronger in At/Nb heterografts than in At/At homografts, and GFP fluorescence was observed in the stock xylem at 7 days after grafting (DAG) in heterografts, a dynamic process absent in At/At homografts. We found that the Atxcp1 mutant promoted the survival of At/Nb interfamilial grafts during the early grafting stage but decreased the survival after several months, indicating delayed incompatibility. Anatomical examination revealed that large cellular deposits accumulated at the graft interface in Atxcp1/Nb interfamilial grafts and exhibited abnormal TE morphology at later stages. Our findings identify AtXCP1 as a key regulator of xylem reconnection and delayed incompatibility in At/Nb interfamilial grafts.