Utility of <i>Arabidopsis KASII</i> Promoter in Development of an Effective CRISPR/Cas9 System for Soybean Genome Editing and Its Application in Engineering of Soybean Seeds Producing Super-High Oleic and Low Saturated Oils

This study reports the use of the <i>Arabidopsis KASII</i> promoter (<i>AtKASII</i>) to develop an efficient CRISPR/Cas9 system for soybean genome editing. When this promoter was paired with <i>Arabidopsis U6</i> promoters to drive Cas9 and single guide RNA expression, respectively, simultaneous editing of the three fatty acid desaturase genes <i>GmFAD2-1A</i>, <i>GmFAD2-1B</i>, and <i>GmFAD3A</i> occurred in more than 60% of transgenic soybean lines at T₂ generation, and all the triple mutants possessed desirable high-oleic traits. In sharp contrast, not a single line underwent simultaneous editing of the three target genes when <i>AtKASII</i> was replaced by the widely used <i>AtEC1.2</i> promoter. Furthermore, our study showed that the stable and inheritable mutations in the high-oleic lines did not alter the overall contents of oil and protein or amino acid composition while increasing the oleic acid content up to 87.6% from approximately 23.8% for wild-type seeds, concomitant with 34.4- and 3.7-fold reductions in linoleic and linolenic acid, respectively. Collectively, this study demonstrates that the <i>AtKASII</i> promoter is highly promising for optimization of the CRISPR/Cas9 system for genome editing in soybean and possibly beyond.