Genome-wide identification and characterization of aquaporin gene family in Beta vulgaris

Aquaporins (AQPs) are essential channel proteins that execute multi-functions throughout plant growth and development, including water transport, uncharged solutes uptake, stress response, and so on. Here, we report the first genome-wide identification and characterization AQP (BvAQP) genes in sugar beet (Beta vulgaris), an important crop widely cultivated for feed, for sugar production and for bioethanol production. Twenty-eight sugar beet AQPs (BvAQPs) were identified and assigned into five subfamilies based on phylogenetic analyses: seven of plasma membrane (PIPs), eight of tonoplast (TIPs), nine of NOD26-like (NIPs), three of small basic (SIPs), and one of x-intrinsic proteins (XIPs). BvAQP genes unevenly mapped on all chromosomes, except on chromosome 4. Gene structure and motifs analyses revealed that BvAQP have conserved exon-intron organization and that they exhibit conserved motifs within each subfamily. Prediction of BvAQPs functions, based on key protein domains conservation, showed a remarkable difference in substrate specificity among the five subfamilies. Analyses of BvAQPs expression, by mean of RNA-seq, in different plant organs and in response to various abiotic stresses revealed that they were ubiquitously expressed and that their expression was induced by heat and salt stresses. These results provide a reference base to address further the function of sugar beet aquaporins and to explore future applications for plants growth and development improvements as well as in response to environmental stresses.