Plant SWEET Family of Sugar Transporters: Structure, Evolution and Biological Functions

Abstract

The SWEET (sugars will eventually be exported transporter) family was identified as a new class of sugar transporters that function as bidirectional uniporters/facilitators and facilitate the diffusion of sugars across cell membranes along a concentration gradient. SWEETs are found widely in plants and play central roles in many biochemical processes, including the phloem loading of sugar for long-distance transport, pollen nutrition, nectar secretion, seed filling, fruit development, plant–pathogen interactions and responses to abiotic stress. This review focuses on advances of the plant SWEETs, including details about their discovery, characteristics of protein structure, evolution and physiological functions. In addition, we discuss the applications of SWEET in plant breeding. This review provides more in-depth and comprehensive information to help elucidate the molecular basis of the function of SWEETs in plants.

Suppression of Cucumber Green Mottle Mosaic Virus Infection by Boron Application: From the Perspective of Nutrient Elements and Carbohydrates

“…The SWEET family plays a vital role in the long-distance transport of sugars, such as glucose, fructose, and sucrose, and NIP5;1 is also involved in sugar transport . In VIGS assays (Figures F and F), the fructose and sucrose contents were higher in leaves, while they were lower in fruits from SWEET4 -silenced plants, which proved that SWEET4 was mainly responsible for the long-distance transport of fructose and sucrose from leaves to fruits.…”

“…Our data revealed that the expression levels of NIP5;1 and SWEET4 were significantly affected by B under CGMMV infection. Additionally, NIP5;1 is a major B channel protein to uptake B, and NIP5;1 and SWEET were all involved in sugar transport. , In consideration of the above reasons, we selected NIP5;1 and SWEET4 for VIGS assays to uncover their roles in viral resistance and the functions for regulating the homeostasis of nutrient elements, soluble sugars, and cell wall polysaccharides.…”

“…SWEETs are involved in the transport of Fe and N and the regulation of the Ca/B balance . In this study, these ion levels in SWEET4 -silenced plants were significantly altered whether in leaves or fruits, indicating that SWEET4 also affected ionic homeostasis in response to CGMMV infection.…”

Grafting enhances plants drought resistance: Current understanding, mechanisms, and future perspectives

“…The accumulation of carbohydrates and nitrogen which need transporter proteins to move to drought-resistant roots, on the one hand, is from detached leaves, and on the other hand, is from photosynthesis ( Yildirim et al., 2018 ; Han et al., 2019 ). The bidirectional sugar transporter (SWEET14) and nitrate transporter 1/peptide transporter (NRT1/PTR), were two significantly accumulating proteins in drought-resistant grapevine rootstock 110R, which promoted the carbohydrates and nitrogen accumulation in roots ( Chen et al., 2012 ; Yildirim et al., 2018 ; Ji et al., 2022 ). Although we believe that during drought stress, transporter proteins will accumulate in the grafted plants, the underlying regulated pathways need further investigation.…”

Genome-Wide Identification and Expression Patterns of the SWEET Gene Family in Bletilla striata and its Responses to Low Temperature and Oxidative Stress

“…Further, it can regulate the uptake of glucose through the cell membrane in the form of glucose transporters, with the function of bidirectional sugar transporters [ 16 ]. A typical SWEET protein consists of seven transmembrane domains (TMs), of which three are more conserved TMs that form the MtN3/saliva structural domain, and the middle is connected by a less conserved TM [ 17 ]. Studies have shown that SWEET proteins can homo- and heterooligomerize to create functional pores; thus, providing transport channels and driving their functions [ 18 ].…”