In Silico Identification and Characterization of Fatty Acid Desaturase (<i>FAD</i>) Genes in <i>Argania spinosa</i> L. Skeels: Implications for Oil Quality and Abiotic Stress

Abstract

Fatty acid desaturase (<i>FAD</i>) is the key enzyme that leads to the formation of unsaturated fatty acids by introducing double bonds into hydrocarbon chains, and it plays a critical role in plant lipid metabolism. However, no data are available on enzyme-associated genes in argan trees. In addition, a candidate gene approach was adopted to identify and characterize the gene sequences of interest that are potentially involved in oil quality and abiotic stress. Based on phylogenetic analyses, 18 putative <i>FAD</i> genes of <i>Argania spinosa</i> L. (<i>AsFAD</i>) were identified and assigned to three subfamilies: stearoyl-ACP desaturase (<i>SAD</i>), Δ-12 desaturase (<i>FAD</i>2/<i>FAD</i>6), and Δ-15 desaturase (<i>FAD</i>3/<i>FAD</i>7). Furthermore, gene structure and motif analyses revealed a conserved exon-intron organization among <i>FAD</i> members belonging to the various oil crops studied, and they exhibited conserved motifs within each subfamily. In addition, the gene structure shows a wide variation in intron numbers, ranging from 0 to 8, with two highly conserved intron phases (0 and 1). The <i>AsFAD</i> and <i>AsSAD</i> subfamilies consist of three (H(X)2-4H, H(X)2-3HH, and H/Q (X)2-3HH) and two (EEN(K)RHG and DEKRHE) conserved histidine boxes, respectively. A set of primer pairs were designed for each <i>FAD</i> gene, and tested on DNA extracted from argan leaves, in which all amplicons of the expected size were produced. These findings of candidate genes in <i>A spinosa</i> L. will provide valuable knowledge that further enhances our understanding of the potential roles of <i>FAD</i> genes in the quality of oil and abiotic stress in the argan tree.