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

ABSTRACT

Nervonic acid (C241) 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 C241 biosynthesis. Xanthoceras sorbifolium is a valuable oil-producing economic woody species with abundant C241 in seed oils, but the key KCS gene responsible for C241 accumulation remains unknown. In this work, a correlation analysis between the transcript profiles of KCS and dynamic change of C241 content in developing seeds of X. sorbifolium were conducted to screen out three members of KCS, namely XsKCS4, XsKCS7 and XsKCS8, potentially involved in C241 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 C241. These findings collectively suggested that XsKCS7 played a crucial role in specific regulation of C241 biosynthesis in X. sorbifolium seeds.