Improved soybean oil quality by targeted mutagenesis of the fatty acid desaturase 2 gene family

Abstract

SummarySoybean oil is high in polyunsaturated fats and is often partially hydrogenated to increase its shelf life and improve oxidative stability. The trans-fatty acids produced through hydrogenation pose a health threat. Soybean lines that are low in polyunsaturated fats were generated by introducing mutations in two fatty acid desaturase 2 genes (FAD2-1A and FAD2-1B), which in the seed convert the monounsaturated fat, oleic acid, to the polyunsaturated fat, linoleic acid. Transcription activator-like effector nucleases (TALENs) were engineered to recognize and cleave conserved DNA sequences in both genes. In four of 19 transgenic soybean lines expressing the TALENs, mutations in FAD2-1A and FAD2-1B were observed in DNA extracted from leaf tissue; three of the four lines transmitted heritable FAD2-1 mutations to the next generation. The fatty acid profile of the seed was dramatically changed in plants homozygous for mutations in both FAD2-1A and FAD2-1B: oleic acid increased from 20% to 80% and linoleic acid decreased from 50% to under 4%. Further, mutant plants were identified that lacked the TALEN transgene and only carried the targeted mutations. The ability to create a valuable trait in a single generation through targeted modification of a gene family demonstrates the power of TALENs for genome engineering and crop improvement.

Genome-Editing Technologies: Principles and Applications

“…Both TALENs and CRISPRCas9 have been used to modify multiple alleles within hexaploid bread wheat to confer heritable resistance to powdery mildew (Wang et al 2014b). In another study, TALENs were used to knock out nonessential genes in the fatty acid metabolic pathway in soybean to generate a simplified plant cell with reduced metabolic components (Haun et al 2014). Of special note, two recent reports showed that purified nuclease proteins can be introduced directly into plant protoplasts, enabling the introduction of germline-transmissible modifications that are virtually indistinguishable from naturally occurring (Luo et al 2015;Woo et al 2015).…”

Genome Editing with Engineered Nucleases in Economically Important Animals and Plants: State of the Art in the Research Pipeline

“…Examples of the transgenic approach include Golden rice with provitamin A content (Beyer et al, 2002) or soybean with decreased α-linolenic fatty acid content (Flores et al, 2008). Seed oil composition in soybean was also the subject in the study by Haun et al (2014) who have used TALENs to knock-out the fatty acid desaturase 2 (fad2) genes. The enzyme catalyzes the conversion of the monounsaturated oleic acid to the polyunsaturated linoleic acid.…”

“…Apart from model plant and animal species, studies have been carried out with economically important organisms and promising results have been obtained. However, a majority of the studies have achieved the mutation only at the cellular level and only a few went on to produce a full-grown organism; especially in the case of animals where the process is more complicated and time-consuming (Shukla et al, 2009;Yu et al, 2011;Lillico et al, 2013;Han et al, 2014;Haun et al, 2014;Luo et al, 2014;Wang et al, 2014;Clasen et al, 2015;Proudfoot et al, 2015). The full-grown animals have been reported to live up to several months of age, but it is not clear yet whether they will maintain normal physiological function through to the adulthood (i.e.…”

“…Probably the most advanced studies are those involving plants, e.g. , Shukla et al (2009), Haun et al (2014, Wang et al (2014) and Clasen et al (2015) that have produced morphologically normal phenotypes with the traits being faithfully transmitted to the next generations. Moreover, the ZFN technique used in Shukla et al (2009) is commercially available as the EXZACT Precision Technology developed and licensed by Dow AgroSciences (http:// www.exzactprecisiontechnology.com).…”

“…There have been several patent applications, e.g. , Haun et al (2014), Clasen et al (2015), however, none of the above mentioned studies have led to commercialization yet.…”