Genome-Wide Analysis of the Fatty Acid Desaturase Gene Family Reveals the Key Role of PfFAD3 in α-Linolenic Acid Biosynthesis in Perilla Seeds

Abstract

Perilla (<i>Perilla frutescens</i>), a traditional medicinal and oilseed crop in Asia, contains extremely high levels of polyunsaturated α-linolenic acid (ALA) (up to 60.9%) in its seeds. ALA biosynthesis is a multistep process catalyzed by fatty acid desaturases (FADs), but the <i>FAD</i> gene family in perilla has not been systematically characterized. Here, we identified 42 <i>PfFADs</i> in the perilla genome and classified them into five subfamilies. Subfamily members of <i>PfFADs</i> had similar exon/intron structures, conserved domain sequences, subcellular localizations, and cis-regulatory elements in their promoter regions. <i>PfFAD</i>s also possessed various expression patterns. <i>PfFAD3.1</i> was highly expressed in the middle stage of seed development, whereas <i>PfFAD7/8.3</i> and <i>PfFAD7/8.5</i> were highly expressed in leaf and later stages of seed development, respectively. Phylogenetic analysis revealed that the evolutionary features coincided with the functionalization of different subfamilies of PUFA desaturase. Heterologous overexpression of <i>PfFAD3.1</i> in <i>Arabidopsis thaliana</i> seeds increased ALA content by 17.68%-37.03%. These findings provided insights into the characteristics and functions of <i>PfFAD</i> genes in perilla.