Spatial and Temporal Localization of Flavonoid Metabolites in Strawberry Fruit (Fragaria × ananassa).

Flavonoids are important metabolites in strawberries (Fragaria X ananassa) because they accomplish an extensive collection of physiological functions and are valuable for human health. However, their localization within the fruit tissue has not been extensively explored. Matrix:assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI) was employed to shed light on the spatial distribution of flavonoids during fruit development. One-wild-type (WT) and two transgenic lines were compared, wherein the transgenic enzymes anthocyanidin reductase (ANRi) and-flavonol synthase (FLSi), respectively, were down-regulated using an RNAi-based silencing approach. In most cases, fruit development led to a reduction Of the investigated flavonoids in the fruit tissue; as a consequence, they were exclusively present in the skin of mature red fruits. In, the case of (epi)catechin diner, both the ANRi and the WT phenotypes revealed low levels in mature:red fruits, whereas the ANRi line bore the lowest relative concentration, as analyzed by liquid chromatography electrospray ionization multiple-step Mass spectrometry (LC=ESI-MS").