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

Changyu Jin,Zixiong Li,Chenhao Gao,Jingyun Gong,Jiangbo Hai,Kaige Liu,Mingxun Chen,Shaowei Duan,Shuanghui Qi,Jianjun Wang,Dong Li

doi:10.3389/fpls.2017.01319

Abstract

Previous studies have shown that several ACYL–ACYL CARRIER PROTEIN DESATURASE (AtAAD) members in Arabidopsis thaliana 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, Brassica napus. Here, we found that AtAAD5 was predominantly and exclusively expressed in developing embryos at the whole seed developmental stages. The aad5 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 BnAAD5-1 from the A3 subgenome of the B. napus inbred line L111. We showed that ectopic expression of BnAAD5-1 in the A. thaliana aad5-2 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 A. thaliana and B. napus and provide a promising target for genetic manipulation of B. napus.

Highlights

Seed fatty acids (FAs) and FA-derived complex lipids provide nutrients for humans and livestock (Li et al, 2006; Graham, 2008), and serve as raw materials for industries and biofuel production (Durrett et al, 2008; Lu et al, 2011)
Previous Reverse transcription-PCR (RT-PCR) results showed that AtAAD5 was widely expressed in A. thaliana tissues, including leaves, stems, roots, flowers, and siliques (Kachroo et al, 2007)
No GUS staining was observed in other tissues, such as expanded true leaves (Figure 1C), cauline leaves (Figures 1D), flowers (Figure 1D), young siliques (Figure 1E), seed coats (Figures 1F–L), or endosperms (Figures 1F–L). These results suggested that AtAAD5 controls seed traits mainly occurring in the A. thaliana embryo at the whole seed developmental stages (Baud et al, 2002; Fait et al, 2006; Graham, 2008; Baud and Lepiniec, 2009)

Summary

Introduction

Seed fatty acids (FAs) and FA-derived complex lipids provide nutrients for humans and livestock (Li et al, 2006; Graham, 2008), and serve as raw materials for industries and biofuel production (Durrett et al, 2008; Lu et al, 2011). Biosynthesis of seed oil is under the control of multiple genes, and occurs in plant cells in three steps (Baud et al, 2008; Itabe, 2010; Chapman and Ohlrogge, 2012). The first step is the production of pyruvate and other substances during glycolysis. Catabolysis of pyruvate and other substances leads to the FA precursor acetyl-CoA, which results in biosynthesis of C16-18 FAs in plastids. FA derivatives are formed at acyl chains.

Methods

Results

Conclusion