Identification and Functional Analysis of a Flavonol Synthase Gene from Grape Hyacinth

Abstract

Flavonols are important copigments that affect flower petal coloration. Flavonol synthase (FLS) catalyzes the conversion of dihydroflavonols to flavonols. In this study, we identified a FLS gene, <i>MaFLS</i>, expressed in petals of the ornamental monocot <i>Muscari aucheri</i> (grape hyacinth) and analyzed its spatial and temporal expression patterns. qRT-PCR analysis showed that <i>MaFLS</i> was predominantly expressed in the early stages of flower development. We next analyzed the in planta functions of <i>MaFLS.</i> Heterologous expression of <i>MaFLS</i> in <i>Nicotiana tabacum</i> (tobacco) resulted in a reduction in pigmentation in the petals, substantially inhibiting the expression of endogenous tobacco genes involved in anthocyanin biosynthesis (i.e., <i>NtDFR</i>, <i>NtANS</i>, and <i>NtAN2</i>) and upregulating the expression of <i>NtFLS</i>. The total anthocyanin content in the petals of the transformed tobacco plants was dramatically reduced, whereas the total flavonol content was increased. Our study suggests that <i>MaFLS</i> plays a key role in flavonol biosynthesis and flower coloration in grape hyacinth. Moreover, <i>MaFLS</i> may represent a new potential gene for molecular breeding of flower color modification and provide a basis for analyzing the effects of copigmentation on flower coloration in grape hyacinth.