Combination of the Elevated Stearic Acid Trait with Other Fatty Acid Traits in Soybean

Abstract

Stearic acid is one of five major fatty acids found in soybean oil. It is a fully saturated lipid and is known for neutral or positive effects on LDL cholesterol when consumed by humans. Unfortunately, stearic acid only accounts for about 4% of the total seed oil produced in commodity soybean. Previous work has shown that stearic acid can reach levels as high as 28% of the total oil fraction when the SACPD‐C gene, encoding the delta‐9‐stearoyl‐acyl carrier protein desaturase responsible for most of the stearic acid variation in soybean seed, is ablated in combination with other loci. In order to increase stearic acid content and create soybeans with improved utility based on fatty acid composition, we combined mutations in SACPD‐C with other mutations in the fatty acid biosynthetic pathway. Soybean plants carrying mutant alleles of both SACPD‐C and FAD2‐1A produce seed with stearic acid levels from 14% to 21%, and with elevated levels of oleic acid. Soybeans carrying mutations in both SACPD‐C and FAD3A or FAD3C have both statistically significantly elevated levels of stearic acid (from 15–21%) and statistically reduced linolenic acid levels. Neither mutant combination appears to affect other agronomic properties such as plant morphology or seed protein levels making this a potentially viable trait.

Construction and Functional Evaluation of CRISPR/Cas9 Multiple Knockout Vectors of the FAD2 Gene Family

“…For example, the down-regulated expression of two homologous FAD2 genes in peanut, based on the CRISPR/Cas9 method, resulted in increased oleic acid levels in stably transformed seeds, compared to the wild type [20]. Soybean seeds with SACPD-C and FAD2-1A mutant alleles showed stearic acid contents from 14% to 21%, while the oleic acid content was increased [25]. CRISPR/Cas9 was used to knock out the GmFATB1 gene, or one or both of them, to produce the mutant.…”

“…The soybean FAD2 gene is expressed differently in different plant tissues, which improves its ability to resist cold and salt stress by regulating the contents of diene fatty acids [20]. It has also been observed that combinations of polyvalent mutants do not seem to affect other agronomic characteristics, such as plant morphology and other quality traits [16,25]. In this study, various agronomic traits of plants of different genotypes were investigated and analyzed during the whole growth period, and it was found that the plant height of the JN38-mutant was significantly higher than that of receptor plants, which might be due to differences in varieties.…”