Phylogenetic analysis of upland cotton MATE gene family reveals a conserved subfamily involved in transport of proanthocyanidins

The multidrug and toxic compound extrusion (MATE) protein belongs to a secondary transporter family, which plays a role in transporting different kinds of substrates like phytohormones and secondary metabolites. In plant, MATE transporters related to the endogenous and exogenous mechanisms of detoxification for secondary metabolites such as alkaloids, flavonoids, anthocyanins and other secondary metabolites have been studied. However, a genome-wide analysis of the MATE family is rarely reported in upland cotton (Gossypium hirsutum L.). In the study, a total of 72 GhMATEs were identified from the genome of upland cotton, which were classified into four subfamilies with possible diverse functions such as transport of proanthocyanidins (PAs), accumulation of alkaloids, extrusion of xenobiotic compounds, regulation of disease resistance and response to abiotic stresses. Meanwhile, the gene structure, evolutionary relationship, physical location, conservative motifs, subcellular localization and gene expression pattern of GhMATEs have been further analysed. Three of these MATE genes (GhMATE12, GhMATE16 and GhMATE38) were identified as candidate genes due to their functions in transport of PA similar to GhTT12. These results provide a new perspective on upland cotton MATE gene family for their potential roles in transport of PA and a theoretical basis for further analyzing the function of MATE genes and improving the fiber quality of brown cotton.