Molecular Cloning, Characterization and Expression Analysis of Auxin Response Factor GhARF2 Gene in Upland Cotton (Gossypium hirsutum L.)

AbstractAuxin response factors (ARFs) are a class of transcription factors that regulate the expression of auxin-responsive genes and play important functions in plant growth and development. To understand the biological functions of the auxin response factorGhARF2gene in upland cotton, the coding sequence (CDS) ofGhARF2gene was cloned, and its protein sequence, evolutionary relationship, subcellular localization and expression pattern were analysed. The results showed that the full-length CDS ofGhARF2gene was 2,583 bp, encoded 860 amino acids, and had a molecular weight and an isoelectric point of 95.46 KDa and 6.02, respectively. The GhARF2 protein had multiple phosphorylation sites, no transmembrane domain, and secondary structures dominated by random coils and α-helices. The GhARF2 protein has 3 conserved typical domains ofARFgene family members, including the B3 DNA binding domain, the Auxin_resp domain, and the Aux/IAA domain. Phylogenetic analysis revealed that ARF2 proteins in different species were clustered in the Group A subgroup, in which GhARF2 was closely related to TcGhARF2 ofTheobroma cacaoL. (Malvaceae). The subcellular localization results showed that the GhARF2 protein was localized in the nucleus. Analysis of tissue expression pattern showed that theGhARF2gene was expressed in all tissues tested, with the highest expression level in sepal, followed by leaf, and the lowest expression level in fiber. Further stress expression analysis showed that theGhARF2gene was induced by drought, high-temperature, low-temperature and salt stress, and had different expression patterns under different stress conditions. These results established a foundation for understanding the functions ofGhARF2and breeding varieties with high-stress resistance in cotton.