Genome-Wide Identification, Characterization, and Expression Profile of SWEETs Gene Family in Grapevine (Vitis vinifera L.)

SWEET (Sugars Will Eventually Be Exported Transporter) proteins, identified recently as a novel class of sugar transporters, play pivotal roles in the transport and distribution of photosynthetic products in plants. They are integral to physiological processes such as response to biotic and abiotic stress, growth and development, and fruit quality formation. In this study, leveraging the latest grapevine genomic data, we identified 18 members of the grapevine SWEET family and named them based on their homologs in Arabidopsis. We conducted a detailed analysis of these protein-encoding genes, focusing on their structure, conserved domains, and phylogenetic relationships. Phylogenetic analysis revealed that the grapevine SWEET family members could be categorized into four clades, with the majority of members displaying relatively conserved gene structures and motifs. Chromosomal localization and homology analysis indicated an uneven distribution of VvSWEETs across 11 chromosomes, with evidence of two segmental duplication events during evolution. Furthermore, we investigated the transcription levels of SWEET genes across different tissues, organs, and developmental stages of fruit, as well as their response patterns under abiotic stress (drought, cold, and salt stress) and biotic stress (Botrytis cinerea infection). Expression profiling demonstrated strong tissue-specificity and temporal-spatial specificity of VvSWEETs, correlated with their respective clades. It is noteworthy that the expression levels of most members within Clade 1 of the VvSWEET gene family, especially VvSWEET1, were markedly upregulated in response to a broad range of stress conditions. Our results provide a comprehensive bioinformatic characterization and analysis of the grapevine SWEET gene family, unveiling the potential functions of grapevine SWEET genes and offering a vital reference for further functional studies.