Genomic analysis of sugar transporter genes in peanut (Arachis hypogaea): Characteristic, evolution and expression profiles during development and stress

Peanut (Arachis hypogaea L.) is an economically significant crop with aerial cleistogamous flowers and subterranean geocarpic fruit (pods). The formation of peanut pod requires movement of the embryo from air to ground and then development in the soil, which is a complex biological process involving transport and accumulation of sugars. Sugar transport proteins (STP) mediate the transport of monosaccharides in various physiological processes, including fertilization, ovary formation, and seed development. In this study, a total of 36 AhSTP genes (AhSTP1–36) containing the conserved sugar_tr motif were identified in the A. hypogaea genome. Phylogenetic analysis revealed that AhSTP genes were classified into four clades, and the arrangement of motifs in AhSTP proteins was similar within clades. Synteny analysis revealed that segmental duplication events have played an important role in the expansion of STP genes in peanut, and chromosome rearrangements might have facilitated the exchange of STP genes between the A and B sub-genomes. Transcriptome analyses revealed that the expression patterns of AhSTP genes varied among tissues. Hormone and abiotic stress treatments could up-regulate or down-regulate the expression of AhSTP genes, and low temperature had a major effect on the expression of most AhSTP genes. Four AhSTP genes (AhSTP3, AhSTP9, AhSTP19, and AhSTP28) were specifically expressed in the pod, indicating that these genes might be involved in pod formation and development in peanut. The unique expression of these four genes during pod construction and development was confirmed in two different type cultivars using quantitative real-time PCR analysis. Our findings provide new insights into the STP gene family in peanut and will aid future functional studies of AhSTP genes.