Overexpression of SmANS Enhances Anthocyanin Accumulation and Alters Phenolic Acids Content in Salvia miltiorrhiza and Salvia miltiorrhiza Bge f. alba Plantlets

Abstract

Flavonoids play multiple roles in plant coloration and stress resistance and are closely associated with human health. Flavonoids and non-flavonoids (such as phenolic acids) are produced via the phenylpropanoid-derived pathway. Anthocyanidin synthase (ANS) catalyzes the synthesis of anthocyanins from leucoanthocyanidin in the flavonoids branched pathway. In this study, <i>SmANS</i> from <i>Salvia miltiorrhiza</i> was cloned and mainly localized in the endoplasmic reticulum (ER), plastids, Golgi, plasma membrane, and nucleus of tobacco epidermal cells, and was most highly expressed in purple petals in <i>S. miltiorrhiza</i>, whereas it showed almost no expression in white petals, green calyxes, and pistils in <i>S. miltiorrhiza</i> Bge f. <i>alba</i>. Overexpressed <i>SmANS</i> enhanced anthocyanin accumulation but reduced salvianolic acid B (SAB) and rosmarinic acid (RA) biosynthesis in <i>S. miltiorrhiza</i> and <i>S. miltiorrhiza</i> Bge f. <i>alba</i> plantlets, meanwhile, it restored the purple-red phenotype in <i>S. miltiorrhiza</i> Bge f. <i>alba</i>. These changes were due to reallocation of the metabolic flow, which was influenced by the <i>SmANS</i> gene. These findings indicate that <i>SmANS</i> not only plays a key role in anthocyanin accumulation in <i>S. miltiorrhiza</i>, but also acts as a "switch" for the coloration of <i>S. miltiorrhiza</i> Bge f. <i>alba</i>. This study provides baseline information for further research on flavonoids metabolism and improvement of anthocyanin or phenolic acid production by genetic engineering.