Genome-Wide Identification of SWEET Gene Family and Its Response to Abiotic Stresses in Valencia Sweet Orange

Abstract

The sugars-will-eventually-be-exported-transporters (SWEET) family is a newly characterized group of sugar transporters, which plays an important role in diverse biological processes, including plant growth, development, and response to abiotic and biotic stresses. SWEET family genes, known as SWEETs, have been characterized in many plant species, but a comprehensive analysis has not been performed on citrus. Here, 27 citrus SWEET genes (CitSWEETs) were identified through homology searches. The phylogenetic relationship, transmembrane helices (TMHs), gene distribution, and gene structure were then investigated. Furthermore, the expression patterns of 27 CitSWEETs were examined in several tissues and under different abiotic stresses. The data revealed that CitSWEET1, CitSWEET2, CitSWEET3, CitSWEET4, CitSWEET7, CitSWEET25, and CitSWEET27 were tissue-specific, and others were ubiquitously expressed. Among 27 genes tested, some members were sensitive to abiotic stress or hormone stimuli, and CitSWEET3 transported glucose in EMY4000 yeast strain. In conclusion, we performed the first comprehensive analysis of the CitSWEET gene family in citrus, which can provide useful information to further analyze their potential roles.