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.
Highlights
The ability of plants to store sugar is essential for their adaptation to endogenous or environmental factors and the economic value of crops, and plants rely on the energy provided by sugars to complete their processes of growth, development and reproduction
The low tolerance of double mutant plants to temperature improved significantly [48]. These results indicate that AtSWEET11 and AtSWEET12 can transport sugar to the secondary xylem to meet the nutrients required for the formation of secondary cell walls, thereby regulating the tolerance of A. thaliana to low-temperature stress [48]
The function of the plant SWEET gene family is closely related to its structure
Summary
Sugar is an important energy source for plants and a necessary carbon source for the synthesis of many of their metabolic intermediates [1–4]. Since sugar is the main transportable form of energy, it participates in the storage and transportation of nutrients in plants and plays an important role in signal transduction and resistance to stress [5–9]. The transportation and distribution of sucrose, glucose and fructose require the participation of sugar transporters [5]. Because the primary product of photosynthesis is sucrose, it is the main carbohydrate that is transported in plants. It is primarily transported and redistributed over long distances through the phloem [23–27]. Studies have shown that SWEETs participate in important physiological processes of plant growth and development by regulating the transportation, distribution and storage of carbohydrates [32,33]. This review introduces the progress of research on the discovery, structural characteristics, physiological functions and regulation of stress by the SWEET gene family, which is of substantial significance to enhance plant breeding efforts in the future
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