Search of candidate genes involved in branched-chain amino acid metabolism in strawberry: functional validation

Abstract

Cultivated strawberry (Fragaria × ananassa) is a berry crop widely appreciated worldwide due to its nutritional and organoleptic properties. However, the main breeding targets in these crops have been the control of flowering (for fruit yield), runnering (for vegetative propagation) and the trade-off between the two. For this reason, nowadays, breeders are mainly focused on recovering fruit quality attributes in order to gain consumers acceptance. Those characteristics are determined by the metabolic composition of the fruit, thus the modulation of its metabolism can help to reach this aim. Regarding aroma, esters are the main responsible of this trait in strawberry fruit. Some of them are derived from the catabolism of branched-chain amino acids (valine, leucine and isoleucine). Although the synthesis of these amino acids has been well stablished in strawberry fruit, its degradation remains unclear. Using a F1 F. × ananassa mapping population we identified a stable QTL (Quantitative Trait Loci) for these amino acids. Based on its differential gene expression in contrasting lines for these metabolites and its annotation, we identified an amino acid transporter as a candidate gene for the regulation of branched-chain amino acid content in strawberry. To elucidate the involvement of this gene in branched-chain amino acid metabolism, we have done functional analysis based on transient overexpression lines on Nicotiana benthamiana showing changes in amino acids content. Currently, we are performing further experiments in order to elucidate the role of this gene on strawberry volatile metabolism.