(+)-Pinoresinol/(−)-lariciresinol reductase from Linum perenne Himmelszelt involved in the biosynthesis of justicidin B

A cDNA encoding a pinoresinol–lariciresinol reductase PLR (PLR-Lp1) was isolated from a cell culture of Linum perenne Himmelszelt accumulating the arylnaphthalene lignan justicidin B. The recombinant PLR-Lp1 prefers (+)-pinoresinol in the first reaction step, but (−)-lariciresinol in the second step. Therefore, it is the first PLR described with opposite enantiospecificity within the two reaction steps catalysed by PLRs. Hairy root lines transformed with an ihpRNAi construct to suppress plr gene expression show less mRNA accumulation for the plr-Lp1 gene and PLR enzyme activity. Justicidin B accumulation was reduced down to 24% in comparison to control lines showing the involvement of PLR-Lp1 in the biosynthesis of justicidin B.