Induction of isoflavonoid pathway in the model legume Lotus japonicus: molecular characterization of enzymes involved in phytoalexin biosynthesis

Treatment of the seedlings of Lotus japonicus, a model legume for molecular genetic studies, with reduced glutathione (GSH) resulted in the accumulati on of an isoflavan phytoalexin, vestitol. Using PCR strategies based on the conserved amino acid sequences, full length P450 cDNAs were obtained from GSH-treated seedling roots. When the clones, LjCYP-1 (CYP93C family) (IFS) and isoflavone 2'-hydroxylase (12'H) activities, respectively. The transcri ption levels of LjCYP-1, LjCYP-2 and isoflavone reductase, which are all in volved in vestitol biosynthesis, coordinately increased upon elicitation. G enomic Southern blot analysis indicated that the IFS gene forms a small gen e Family and a single copy of the 12'H gene is present in the L. japonicus genome. Molecular biological aspects of P450s involved in the isoflavonoid pathway and the genomic approach to flavonoid metabolism in this unique pla nt are discussed. (C) 2000 Elsevier Science Ireland Ltd. All rights reserve d.