CRISPR/Cas9-Mediated Gene Editing of BnFAD2 and BnFAE1 Modifies Fatty Acid Profiles in Brassica napus

Fatty acid (FA) composition determines the quality of oil from oilseed crops, and thus is a major target for genetic improvement. FAD2 (Fatty acid dehydrogenase 2) and FAE1 (fatty acid elongase 1) are critical FA synthetic genes, and have been the focus of genetic manipulation to alter fatty acid composition in oilseed plants. In this study, to improve the nutritional quality of rapeseed cultivar CY2 (about 50% oil content; of which 40% erucic acid), we generated novel knockout plants by CRISPR/Cas9 mediated genome editing of BnFAD2 and BnFAE1 genes. Two guide RNAs were designed to target one copy of the BnFAD2 gene and two copies of the BnFAE1 gene, respectively. A number of lines with mutations at three target sites of BnFAD2 and BnFAE1 genes were identified by sequence analysis. Three of these lines showed mutations in all three target sites of the BnFAD2 and BnFAE1 genes. Fatty acid composition analysis of seeds revealed that mutations at all three sites resulted in significantly increased oleic acid (70–80%) content compared with that of CY2 (20%), greatly reduced erucic acid levels and slightly decreased polyunsaturated fatty acids content. Our results confirmed that the CRISPR/Cas9 system is an effective tool for improving this important trait.