Sugars are the major source of energy in living organisms and play important roles in osmotic regulation, cell signaling and energy storage. SWEETs (Sugars Will Eventually be Exported Transporters) are the most recent family of sugar transporters that function as uniporters, facilitating the diffusion of sugar molecules across cell membranes. In plants, SWEETs play roles in multiple physiological processes including phloem loading, senescence, pollen nutrition, grain filling, nectar secretion, abiotic (drought, heat, cold, and salinity) and biotic stress regulation. In this review, we summarized the role of SWEET transporters in plant development and abiotic stress. The gene expression dynamics of various SWEET transporters under various abiotic stresses in different plant species are also discussed. Finally, we discuss the utilization of genome editing tools (TALENs and CRISPR/Cas9) to engineer SWEET genes that can facilitate trait improvement. Overall, recent advancements on SWEETs are highlighted, which could be used for crop trait improvement and abiotic stress tolerance.

Wheat is one of the most important cereal crop in the world. Heat stress is an important abiotic stress limiting wheat production and productivity in the world including south-east Asia. The importance of miRNAs in gene expression under various biotic and abiotic stresses is well documented. Molecular markers, especially SSR markers, plays an important role for the success in molecular plant breeding programs. The discovery of SSRs from non-coding regions has been a challenging task. Therefore, development of novel miRNA-based SSRs from the conserved portions of the genome will prove useful for the study of genetic diversity of heat-responsive miRNA-genes in wheat. In the present study, efforts are made to mine SSR markers from 96 members of heat-responsive miRNA-genes of wheat followed by their validation using 37 contrasting (heat tolerance/susceptible) wheat genotypes. Among a set of 13 miRNA-SSRs used,7 SSRs were found polymorphic. Among these polymorphic SSR markers, three found to be very informative SSRs (HT-169j, HT-160a and HT-160b) and could largely discriminate heat tolerant genotypes from the heat susceptible ones. Further analysis based on Polymorphism Information Content (PIC) revealed that miRNA genes were more diverse in susceptible genotypes compared to tolerant genotypes. Ours is the first report that the genic/miRNA markers could be successfully used to study wheat diversity, population structure and characterization of trait specific germplasm. The important and useful miRNA-based SSRs, therefore, would serve as best markers in the marker-assisted breeding programs aimed at enhancing heat tolerance of Indian wheat.