Differential expression of two flavonoid 3′-hydroxylase cDNAs involved in biosynthesis of anthocyanin pigments and 3-deoxyanthocyanidin phytoalexins in sorghum

Abstract

Three unique sorghum flavonoid 3′-hydroxylase (F3′H) cDNAs (SbF3′H1, SbF3′H2 and SbF3′H3) were discovered through bioinformatics analysis. Their encoded proteins showed >60% identity to the Arabidopsis TT7 (F3′H) protein. Overexpression of SbF3′H1 or SbF3′H2 restored the ability of tt7 mutants to produce 3′-hydroxylaed flavonoids, establishing their roles as functional F3′H enzymes. In sorghum mesocotyls, SbF3′H1 expression was involved in light-specific anthocyanin accumulation while SbF3′H2 expression was involved in pathogen-specific 3-deoxyanthocyanidin synthesis. No SbF3′H3 expression was detected in all tissues examined. The sorghum mesocotyls represent a good system for investigation of differential regulation of F3′H genes/alleles responding to different external stimuli. © The Author 2006. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved.