Generation of purple-violet chrysanthemums via anthocyanin B-ring hydroxylation and glucosylation introduced from Osteospermum hybrid F3'5'H and Clitoria ternatea A3'5'GT

Abstract

Chrysanthemums possess no metabolic pathway to synthesize delphinidin because of the lack of endogenous F3'5'H gene encoding the key enzyme in its biosynthetic pathway; therefore, there are no blue or blue-purple chrysanthemums occurring naturally. Currently, the introduction of exogenous F3'5'H into chrysanthemums is an efficient method for breeding bluish chrysanthemums. In this study, we explored the effects of the introduction of mutant CmF3'H (generated via site-directed mutagenesis, T485S, CmF3'Hm) and exogenous Osteospermum hybrid F3'5'H (OhF3'5'H) genes combined with Clitoria ternatea A3'5'GT (CtA3'5'GT) on delphinidin synthesis in chrysanthemum. Among the F3'5'H transgenic lines, those overexpressing endogenous CmF3'Hm could not generate blue flower color, although red color was changed to light pink due to CtA3'5'GT function. Meanwhile, OhF3'5'H introduction promoted the accumulation of delphinidin and its derivatives in chrysanthemum, changing the flower color from red-purple to purple-violet. These results indicate the applicability of exogenous OhF3'5'H and CtA3'5'GT transformation for promoting delphinidin synthesis during the molecular breeding of violet/blue chrysanthemums.