Conserved Function of ACYL–ACYL CARRIER PROTEIN DESATURASE 5 on Seed Oil and Oleic Acid Biosynthesis between Arabidopsis thaliana and Brassica napus

Abstract

Previous studies have shown that several ACYL-ACYL CARRIER PROTEIN DESATURASE (AtAAD) members in <i>Arabidopsis thaliana</i> are responsible for oleic acid (C18:1) biosynthesis. Limited research has been conducted on another member, AtAAD5, and its paralog BnAAD5 in the closely related and commercially important plant, <i>Brassica napus</i>. Here, we found that <i>AtAAD5</i> was predominantly and exclusively expressed in developing embryos at the whole seed developmental stages. The <i>aad5</i> mutation caused a significant decrease in the amounts of oil and C18:1, and a considerable increase in the content of stearic acid (C18:0) in mature seeds, suggesting that AtAAD5 functioned as an important facilitator of seed oil biosynthesis. We also cloned the full-length coding sequence of <i>BnAAD5-1</i> from the A3 subgenome of the <i>B. napus</i> inbred line L111. We showed that ectopic expression of <i>BnAAD5-1</i> in the <i>A. thaliana aad5-2</i> mutant fully complemented the phenotypes of the mutant, such as lower oil content and altered contents of C18:0 and C18:1. These results help us to better understand the functions of AAD members in <i>A. thaliana</i> and <i>B. napus</i> and provide a promising target for genetic manipulation of <i>B. napus</i>.