Salix matsudana fatty acid desaturases: Identification, classification, evolution, and expression profiles for development and stress tolerances.

Fatty acid desaturases (FADs) are enzymes that transform carbon‑carbon single bonds into carbon‑carbon double bonds within acyl chains, resulting in the production of unsaturated FAs (UFAs). They are crucial for plant growth, development, and adaptation to environmental stress. In our research, we identified 40 FAD candidates in the Salix matsudana genome, grouping them into seven categories. Exon-intron structures and conserved motifs of SmFADs within the same group showed significant conservation. Cis-element analysis revealed SmFADs are responsive to hormones and stress. Additionally, GO and KEGG analyses linked SmFADs closely with lipid biosynthesis and UFA biosynthesis, which were crucial for the plant's response to environmental stresses. Notably, the SmFAB2.4, SmADS1, SmFAD7.5, and SmFAD8.2 were predicted to participate in submergence tolerance, whereas SmFAD8.1 and SmFAD7.1 played an essential role in salt stress response. The diverse expression profiles of SmFADs across willow varieties, in various tissues, and throughout the willow bud development stages revealed a spectrum of functional diversity for these genes. Moreover, specific SmFADs might play a crucial role in callus development and the response to culturing conditions in various willow cultivars. This research underscored the importance of SmFAD profiles and functions and identified potential genes for enhancing forest resilience.