Increased Production of α-Linolenic Acid in Soybean Seeds by Overexpression of Lesquerella FAD3-1
Wan Woo Yeom, Hye Jeong Kim, Hye Jeong Kim, Kyeong‐Ryeol Lee, Hyun Suk Cho, Jinyoung Kim, Ho Won Jung, Seon‐Woo Oh, Sang Eun Jun, Hyun Uk Kim, Hyun Uk Kim, Young‐Soo Chung
Abstract
Soybean is a major crop that is used as a source of vegetable oil for human use. To develop transgenic soybean with high ɑ-linolenic acid (ALA; 18:3) content, the FAD3-1 gene isolated from lesquerella (Physaria fendleri) was used to construct vectors with two different seed-specific promoters, soybean β-conglycinin (Pβ-con) and kidney bean phaseolin (Pphas), and one constitutive cauliflower mosaic virus 35S promoter (P35S). The corresponding vectors were used for Agrobacterium-mediated transformation of imbibed mature half seeds. The transformation efficiency was approximately 2%, 1%, and 3% and 21, 7, and 17 transgenic plants were produced, respectively. T-DNA insertion and expression of the transgene were confirmed from most of the transgenic plants by polymerase chain reaction (PCR), quantitative real-time PCR (qPCR), reverse transcription PCR (RT-PCR), and Southern blot analysis. The fatty acid composition of soybean seeds was analyzed by gas chromatography. The 18:3 content in the transgenic generation T1 seeds was increased 7-fold in Pβ-con:PfFAD3-1, 4-fold in Pphas:PfFAD3-1, and 1.6-fold in P35S:PfFAD3-1 compared to the 18:3 content in soybean ‘Kwangankong.’ The increased content of 18:3 in the Pβ-con:PfFAD3-1 soybean (T1) resulted in a 52.6% increase in total fatty acids, with a larger decrease in 18:1 content than 18:2 content. The increase in 18:3 content was also maintained and reached 42% in the Pphas:PfFAD3-1 transgenic generation T2. Investigations of the agronomic traits of 12 Pβ-con:PfFAD3-1 transgenic lines (T1) revealed that plant height, number of branches, nodes, pods, total seeds and total seed weight were significantly higher in several transgenic lines than in non-transgenic soybean. Especially, an increase in seed size was observed upon expression of the PfFAD3-1 gene with the β-conglycinin promoter, and 6–14% higher seed lengths were measured from the transgenic lines.