Identification and Evolutionary Analysis of FAD2 Gene Family in Green Plants

Abstract

Fatty acid desaturase 2 (FAD2) is a crucial enzyme in the biosynthesis of polyunsaturated fatty acids in plants, which introduce a double bond into oleic acid to produce linoleic acid. FAD2 is imperative to the application and nutritional value of vegetable oil as both oleic acid and linoleic acid are the primary constituent fatty acids and their relative proportion determines the nutritional value and oxidative stability in most temperate vegetable oils. In the study described herein, we have identified a total of 253 candidate FAD2 genes from the published genomes of 79 plants. Phylogenetic analysis showed that FAD2 genes in green plants can be divided into three categories, namely, eudicots, monocots and lower plants (except Amborella trichopoda). Through the analysis of its conserved domains, all FAD2 genes contain motifs harbouring HECGH, HRRHH and HVAHH, −the three histidine clusters that are important functional structures of FAD2 gene. According to exon/intron structure analysis, the number of introns varies greatly in lower plants. With the evolution of green plants, the number of introns decreases. This study found that introns were mainly located in the 5’UTR and CDs regions, and their length ranged from 4 bp to 11,233 BP. In addition, about 56% of the 3 ‘and 5’ ends of FAD2 are located at Ag: GT, and the total content of a and t is generally about 60%.Through other bioinformatics methods, we concluded that FAD2 was more conservative in the process of plant evolution. This study provides theoretical support for further analysis of FAD2 gene family evolution.