Cloning, expression and molecular modeling of the anthocyanidin reductase (FaANR) gene during strawberry fruit development

Introduction - Proanthocyanidins (PAs) are a group of polyphenolic secondary metabolites synthesized in plants via flavonoid pathway. Strawberry (Fragaria x ananassa Duch.) is a rich source of flavonoids and proanthocyanins, which are known to have multiple health benefits. The anthocyanidin reductase (ANR) is an interesting gene to study within the flavonoid biosynthesis pathway, since it diverts the anthocyanin pathway to flavonol synthesis. Materials and methods - The present study describes cloning, semi-quantitative expression analysis and molecular modeling of the strawberry (cv. Sweet Charlie) anthocyanidin reductase (FaANR) gene during the progressive stages of fruit development. Results and discussion - The FaANR gene was 1,020 bp long with an open reading frame encoding a protein of 308 amino acid residues. The estimated molecular mass and isoelectric point of the protein were 32.89 kD and 5.54, respectively. The expression of FaANR was only seen during early stages of fruit development indicating its early involvement in PA accumulation, well before ripening onset. Analysis of the FaANR sequence showed 98% similarity to ANR from diploid strawberry Fragaria vesca. The cladistic analysis indicated that the FaANR was phylogenetically similar to Pyrus and Prunus ANR genes. Protein modeling suggested protein-ligand interactions at active site with NADP binding as the plausible mechanism of action. Conclusion - This is the first report on cloning, expression study and in silico modeling of an anthocyanidin reductase of strawberry. The conditions of in vivo modulation of ANR expression open applied perspectives for commercial production of PAs in strawberry and other berries.