Physiological implications of SWEETs in plants and their potential applications in improving source–sink relationships for enhanced yield

Abstract

The sugars will eventually be exported transporters (SWEET) family of transporters in plants is identified as a novel class of sugar carriers capable of transporting sugars, sugar alcohols and hormones. Functioning in intercellular sugar transport, SWEETs influence a wide range of physiologically important processes. SWEETs regulate the development of sink organs by providing nutritional support from source leaves, responses to abiotic stresses by maintaining intracellular sugar concentrations, and host-pathogen interactions through the modulation of apoplastic sugar levels. Many bacterial and fungal pathogens activate the expression of SWEET genes in species such as rice and Arabidopsis to gain access to the nutrients that support virulence. The genetic manipulation of SWEETs has led to the generation of bacterial blight (BB)resistant rice varieties. Similarly, while the overexpression of the SWEETs involved in sucrose export from leaves and pathogenesis led to growth retardation and yield penalties, plants overexpressing SWEETs show improved disease resistance. Such findings demonstrate the complex functions of SWEETs in growth and stress tolerance. Here, we review the importance of SWEETs in plant-pathogen and source-sink interactions and abiotic stress resistance. We highlight the possible applications of SWEETs in crop improvement programmes aimed at improving sink and source strengths important for enhancing the sustainability of yield. We discuss how the adverse effects of the overexpression of SWEETs on plant growth may be overcome.

Camellia oleifera CoSWEET10 Is Crucial for Seed Development and Drought Resistance by Mediating Sugar Transport in Transgenic Arabidopsis

“…SWEET transporters in plants are mostly involved in intercellular sugar transport, and contribute to the growth of sink organs by translocating carbohydrates from source leaves to sinks [37]. Phylogenetic analysis has shown that CoSWEET10 belongs to Clade III of the SWEET family and has the highest homology with Arabidopsis AtSWEET10, which also belongs to Clade III.…”

“…The GmSWEET15a and 15b in soybeans mediate the transport of sucrose from the endosperm to the embryo [38], while GmSWEET10a and GmSWEET10b influence the seed size and oil content by transporting both sucrose and glucose from the seed coat to the embryo [18]. SWEETs not only function as sugar transporters but also as sugar alcohol and hormone carriers [37]. For example, Clade III members AtSWEET13 and 14 are capable of transporting sucrose and are involved in gibberellic acid (GA) transport [39].…”

Coordination of carbon assimilation, allocation, and utilization for systemic improvement of cereal yield

“…Phloem tissue is composed of three cell types: companion cells (CC), sieve elements (SE), and phloem parenchyma cells (PP), which act as highway linking sources and sinks for sugar transport. Proteins responsible for sugar transport, including SUT, SWEETs, and monosaccharide transporters (MTs), have receive much attention ( Julius et al., 2017 ; Braun, 2022 ; Xue et al., 2022 ; Singh et al., 2023 ). Here, we focus on maize, rice, and wheat and discuss the importance of the coordination of C transport for crop production in some recent cases.…”

Genome-wide analysis of the SWEET gene family in Hemerocallis citrina and functional characterization of HcSWEET4a in response to salt stress

“…As a transporter identi ed about sugars recently, the SWEETs are found to be present in all kingdoms of life [5,9]. SWEET proteins play central roles in plant growth and development such as plant defense, long-distance transport of sucrose, vegetative and reproduction growth, senescence, and stress responses [12][13][14]. Currently, four SWEETs clades have been reported in plants, respectively Clade I, II, III, and IV, furthermore genes belonging to the same clade hold similar structures and functions [8,15].…”