Understanding the role of SWEET genes in fruit development and abiotic stress in pomegranate (Punica granatum L.)

BACKGROUND The Sugar Will Eventually Be Exported Transporters (SWEET), consisting of the MtN3 and salvia domain, are sugar transporters having an active role in diverse activities in plants such as pollen nutrition, phloem loading, nectar secretion, reproductive tissue development, and plant-pathogen interaction. The SWEET genes have been characterized only in a few fruit crop species. METHODS AND RESULTS In this study, a total of 15 SWEET genes were identified in the pomegranate (Punica granatum) genome. The gene structure, transmembrane (TM) helices, domain architecture, and phylogenetic relationships of these genes were evaluated using computational approaches. Genes were further classified as Semi-SWEETs or SWEETs based on the TM domains. Similarly, pomegranate, Arabidopsis, rice, and soybean SWEETs were studied together to classify into major groups. In addition, analysis of RNAseq transcriptome data was performed to study SWEEET gene expression dynamics in different tissue. The expression suggests that SWEETs are mostly expressed in pomegranate peel. In addition, PgSWEET13 was found to be differentially expressed under high salinity stress in pomegranate. Further, quantitative PCR analysis confirmed the expression of four candidate genes in leaf and stem tissues. CONCLUSION The information provided here will help to understand the role of SWEET genes in fruit development and under abiotic stress conditions in pomegranate.