Molecular characterizatiom of a flavone synthase gene in sorghum

Abstract

More than 9000 different flavonoids have been described in plants and flavones are one of the major classes of flavonoids. They exhibit diverse functions in plant physiology, biochemistry and ecology. In addition, they are known to have significant pharmacological properties including anti-oxidation, anti-anxiety and antiestrogenic effects as well as prevention of coronary heart diseases. In this study, three flavones, luteolin, apigenin and tricin, were identified in infected seedlings of different sorghum cultivars which are susceptible or resistant to Colletotrichum sublineolum, the causal agent of sorghum anthracnose. The levels of the different flavones were quantified by liquid chromatography-tandem mass spectrometry in multiple-reactions-monitoring mode. In bioassay experiments, luteolin showed higher inhibitory effects on spore germination of C. sublineolum than apigenin. A pathogen-inducible gene, SbFNSII, which was predicted to encode a P450 enzyme, was demonstrated to be involved in flavone synthesis in transgenic plants. Glycosides of luteolin and apigenin were identified in SbFNSII-overexpressing Arabidopsis lines. To our knowledge, SbFNSII represents the first example of a flavone synthase gene in monocots.