Gene Encodes a Flavonoid Prenyltransferase in White Lupin.

Legume plants are rich in prenylated flavonoid compounds, which play an important role in plant defense and human health. In the present study, we identified a prenyltransferase (PT) gene, named , in white lupin (), which shows a high identity and close relationship with the other known PT genes involved in flavonoid prenylation in planta. The recombinant LaPT2 protein expressed in yeast cells exhibited a relatively strong activity toward several flavonols (e.g., kaempferol, quercetin, and myricetin) and a relatively weak activity toward flavanone (naringenin). In addition, the recombinant LaPT2 protein was also active toward several other types of flavonoids, including galangin, morin, 5-deoxyquercetin, 4'-O-methylkaempferol, taxifolin, and aromadendrin, with distinct enzymatic affinities. The gene was preferentially expressed in the roots, which is consistent with the presence of prenylated flavonoid kaempferol in the roots. Moreover, we found that the expression level of paralleled with those of and genes that were relatively higher in roots and lower in leaves, suggesting that they were essential for the accumulation of prenylated flavonoid kaempferol in roots. The deduced full-length LaPT2 protein and its signal peptide fused with a green fluorescent protein (GFP) are targeted to plastids in the protoplast. Our study demonstrated that from white lupin is responsible for the biosynthesis of prenylated flavonoids, in particular flavonols, which could be utilized as phytoalexin for plant defense and bioactive flavonoid compounds for human health.