Insights into the Role of GhTAT2 Genes in Tyrosine Metabolism and Drought Stress Tolerance in Cotton

<i>Gossypium hirsutum</i> is a key fiber crop that is sensitive to environmental factors, particularly drought stress, which can reduce boll size, increase flower shedding, and impair photosynthesis. The aminotransferase (AT) gene is essential for abiotic stress tolerance. A total of 3 <i>Gossypium</i> species were analyzed via genome-wide analysis, and the results unveiled 103 genes in <i>G. hirsutum</i>, 47 in <i>G. arboreum</i>, and 53 in <i>G. raimondii</i>. Phylogenetic analysis, gene structure examination, motif analysis, subcellular localization prediction, and promoter analysis revealed that the <i>GhAT</i> genes can be classified into five main categories and play key roles in abiotic stress tolerance. Using RNA-seq expression and KEGG enrichment analysis of <i>GhTAT2</i>, a coexpression network was established, followed by RT-qPCR analysis to identify hub genes. The RT-qPCR results revealed that the genes <i>Gh_A13G1261</i>, <i>Gh_D13G1562</i>, <i>Gh_D10G1155</i>, <i>Gh_A10G1320</i>, and <i>Gh_D06G1003</i> were significantly upregulated in the leaf and root samples following drought stress treatment, with <i>Gh_A13G1261</i> identified as the hub gene. The <i>GhTAT2</i> genes were considerably enriched for tyrosine, cysteine, methionine, and phenylalanine metabolism and isoquinoline alkaloid, tyrosine, tryptophan, tropane, piperidine, and pyridine alkaloid biosynthesis. Under drought stress, KEGG enrichment analysis manifested significant upregulation of amino acids such as L-DOPA, L-alanine, L-serine, L-homoserine, L-methionine, and L-cysteine, whereas metabolites such as maleic acid, p-coumaric acid, quinic acid, vanillin, and hyoscyamine were significantly downregulated. Silencing the <i>GhTAT2</i> gene significantly affected the shoot and root fresh weights of the plants compared with those of the wild-type plants under drought conditions. RT-qPCR analysis revealed that <i>GhTAT2</i> expression in VIGS-treated seedlings was lower than that in both wild-type and positive control plants, indicating that silencing <i>GhTAT2</i> increases sensitivity to drought stress. In summary, this thorough analysis of the gene family lays the groundwork for a detailed study of the <i>GhTAT2</i> gene members, with a specific focus on their roles and contributions to drought stress tolerance.