Comprehensive analysis of amino acid/auxin permease family genes reveal the positive role of GhAAAP128 in cotton tolerance to cold stress

Amino acid/auxin permeases (AAAPs) play crucial roles in plant development and response to environmental stimuli. They have been characterized at genome-wide levels in several plant species. However, little is known about the AAAP genes in Gossypium. Here, we identified 149, 141, 73, and 70 AAAPs from G. hirsutum, G. barbadense, G. arboreum, and G. raimondii, respectively. All the AAAPs were categorized into eight subfamilies (Groups I-VIII). Moreover, we found that 182 and 179 AAAP paralogous gene pairs existed within G. hirsutum and G. barbadense genomes, respectively, and whole genome duplication (WGD) or segmental duplication contributed to the expansion of these AAAPs during evolution. Additionally, many cis-elements related to abiotic stress responses were detected in the promoter regions of GhAAAPs and GbAAAPs. Consistently, the expression of multiple AAAPs was significantly induced by NaCl, polyethylene glycol 6000, and especially cold stress. Among these GhAAAPs, GhAAAP128 had clearly positive roles in cotton and Arabidopsis seedling tolerance to cold stress. It may improve plant cold tolerance by up-regulating the expression of some anthocyanin synthesis genes rather than CBF (C-repeat binding factor) signaling genes. Our findings provide important information for further functional analysis of GhAAAPs in response to stressful cues, particularly cold stress in cotton plants.