3-ketoacyl-CoA synthase 7 from Xanthoceras sorbifolium seeds is a crucial regulatory enzyme for nervonic acid biosynthesis

Nervonic acid (C24:1) is a very-long-chain fatty acid that plays an imperative role in human brain development and other health benefits. In plants, 3-ketoacyl-CoA synthase (KCS) is the key rate-limiting enzyme for C24:1 biosynthesis. Xanthoceras sorbifolium is a valuable oil-producing economic woody species with abundant C24:1 in seed oils, but the key KCS gene responsible for C24:1 accumulation remains unknown. In this work, a correlation analysis between the transcript profiles of KCS and dynamic change of C24:1 content in developing seeds of X. sorbifolium were conducted to screen out three members of KCS, namely XsKCS4, XsKCS7 and XsKCS8, potentially involved in C24:1 biosynthesis. Of which, the XsKCS7 was highly expressed in developing seeds, while XsKCS4 and XsKCS8 displayed the highest expression in fruits and flowers, respectively. Overexpression of XsKCS4, XsKCS7 and XsKCS8 in yeast Saccharomyces cerevisiae and plant Arabidopsis thaliana indicated that only XsKCS7 possessed the ability to facilitate the biosynthesis of C24:1. These findings collectively suggested that XsKCS7 played a crucial role in specific regulation of C24:1 biosynthesis in X. sorbifolium seeds. ●XsKCS7 as crucial protein for C24:1 accumulation of X. sorbifolium.●XsKCS7 is high-expressed in developing seeds.●Ectopic overexpression of XsKCS7 prompted seed C22:1 and C24:1 accumulation.●Potential of XsKCS7 to engineering C24:1 accumulation in oil plants.