Genome-wide analysis and functional validation of the cotton FAH gene family for salt stress

Fatty acid hydroxylases (FAHs) are a family of enzymes that includes fatty acid hydroxylases, carotenoid hydroxylases, and sterol desaturases. Fatty acids are highly important for plants. They are the main source of energy storage and the main component of the cell membrane. Saturated fatty acids can be divided into two categories: saturated fatty acids and unsaturated fatty acids. FAHs play a pivotal role in enhancing plant salt tolerance by modulating fatty acid metabolic pathways, thereby improving cell membrane stability and antioxidant capacity. In this study, we identified a total of 129 FAH gene family members in four cotton species, namely, Gossypium hirsutum, Gossypium darwinii, Gossypium arboreum, and Gossypium raimondii. The FAH genes were divided into five subgroups via evolutionary analysis. FAH genes located in the same subgroup presented similar gene structures and a consistent distribution of conserved motifs through the analysis of evolutionary trees, gene structures, and conserved motifs. Chromosomal localization analysis of the FAH gene family revealed that it has undergone chromosomal segment duplication events. Analysis of cis-acting elements suggested that the FAH gene may be involved in regulating biotic and abiotic stresses, plant growth and development, signaling pathways, and other physiological processes. The RT‒qPCR results revealed significant differences in the expression levels of FAH gene family members under salt stress conditions compared with those in the control group. Additionally, we successfully silenced Gohir.A03G045300 through VIGS experiments, and the results indicated that the silenced plants were more sensitive to salt stress than the control plants were. This suggests that Gohir.A03G045300 may be involved in the response of cotton to salt stress. A total of 129 FAH genes were identified in four Gossypium species through bioinformatics analysis. Gene silencing of FAH members in G. hirsutum revealed that the FAH gene family plays a crucial role in the response of cotton to salt stress.