Cloning and expression analysis of leucoanthocyanidin reductase gene in Fagopyrum dibotrys / 药学学报

The leucoanthocyantin reducase (LAR) gene, an important functional gene of catechins biosynthesis pathway, was cloned from Fagopyrum dibotrys (D.Don) Hara by degenerate PCR and rapid amplification of cDNA ends (RACE). The full-length cDNA of FdLAR is 1 581 bp (GenBank accession: JN793953), containing a 1 176 bp ORF encoding a 391 amino acids protein, and its 3'-untranslated region has an obvious polyadenylation signal. The recombinant plasmid containing FdLAR completed ORF was transformed into E. coli BL21 (DE3). The target fusion peptide with molecular weight of 66 kD was expressed under the condition of 16 degrees C and induced by IPTG at final concentration of 1.0 mmol x L(-1). Bioinformation analysis indicated that the amino acid sequence of FdLAR showed great homology to other LAR with the NADB-Rossmann conversed domain in the N-terminus. Real-time quantitative PCR was used to detect the expression levels of FdLAR gene during different development periods. The determination of flavonoids contents in appropriate rhizomes showed that the relationship between FdLAR gene expression and the accumulation of flavonoids displayed different trends during vegetative growth and reproductive growth stages, suggesting that the FdLAR gene may be involved in the pathway of flavonoid metabolisms in Fagopyrum dibotrys.

Molecular cloning and characterization of a novel isoflavone reductase-like gene (FcIRL) from high flavonoids-producing callus of Fagopyrum cymosum / 药学学报

Lignans are important defensive compounds in plants and have good biological activities protecting human health. In order to study the medicinal secondary metabolism of Fagopyrum cymosum (Trev.) Meisn, a traditional Chinese medicine with anti-tumor effect, a novel isoflavone reductase-like gene, FcIRL, was cloned using RACE strategy from a cDNA library of high flavonoids-producing callus. The full-length cDNA of the FcIRL was 1 217 bp (accession no. EU116032), which contained a 942 bp open reading frame (ORF) encoding a 313 amino acid protein. Two stop codons (TAG) and a putative polyadenylation signal ATAAA at 24 bp upstream from the polyadenylation site was found in 5' and 3' UTR, separately. And no intron was found in the genomic sequence yet. FcIRL contained a predicted N-terminal acetylation site (M1-K5) and a NADPH-binding motif (G10-G-T-G13-Y-I-G16) in the N-terminal region, a conserved NmrA (nitrogen metabolite repression regulator) domain (V6-N244), multi-phosphorylation sites and one conserved N-glycosylation site (N214). Sequence homology comparison, phylogenetic analysis and advanced structures prediction all suggested that FcIRL belonged to the class of pinoresinol-lariciresinol reductase (PLR), which is a key enzyme in synthetic pathway of 8-8'-linked lignans, with function in catalyzing reduction of pinoresinol and lariciresinol into secoisolariciresinol, and medicinal secondary metabolism and resistance in F. cymosum.