Postharvest Biochemistry

Controlled atmosphere (CA) storage is a postharvest management technology designed to limit respiration and ethylene-mediated processes leading to the loss of fruit quality and freshness, and also serves to increase the marketability of climacteric fruit. For some pome cultivars, CA storage may also result in the development of physiological disorders of the fruit surface and/or flesh. My lab is interested in the relationship between oxidative stress metabolism and the onset of physiological disorders in bulky fruit (e.g. apples and pears) during CA storage. Currently, we are focused on developing cultivar-specific strategies for prolonged CA storage of traditional and newly developed pome fruits cultivated in Ontario. To date, the biochemical processes promoting the onset of physiological disorders in response to CA are unknown. To address this, we are conducting studies to determine whether an imbalance in whole fruit redox metabolites (i.e. ascorbate and glutathione) precedes physiological disorders in apple and pears during CA storage.

Secondary Metabolism

An on-going interest in the laboratory is to define biochemical signatures that are pivotal for the modification and/or catabolism of phenylpropanoid pathway end products in planta. Briefly, we are studying the metabolism of the following phenylpropanoid derived products: flavonols, potential human health promoting compounds; anthocyanins, red, blue and purple pigments formed in fruits, flowers and seeds; and proanthocyanidins.

Flavonol Catabolism in Plants

My laboratory is investigating the key biochemical and molecular determinants promoting the loss of flavonols, specifically kaempferol and quercetin bisglycosides in vegetative plant tissues of Arabidopsis thaliana. These bisglycosides accumulate in leaves and roots in response to abiotic stress, and have been shown to rapidly disappear within a few days of stress recovery. To date, the catabolic products of kaempferol and quercetin bisglycosides, as well as the enzymes promoting their loss in Arabidopsis are scantly described. We are using biochemical tools together with functional genomics to elucidate the major enzymatic steps required for the degradation of stress-inducible quercetin bisglycosides.

Seed Coat Darkening and the Phenylpropanoid Pathway

Research aims to determine the key structural and regulatory steps of the phenylpropanoid pathway underlying the seed coat darkening phenomenon in edible dry beans (Phaseolus vulgaris). The oxidation of seed coat proanthocyanidins during the postharvest handling of dry beans culminates in the browning of the seed coat. We are using RNAseq technology to determine the difference in phenylpropanoid pathway gene expression in darkening relative to non-darkening cranberry beans. In addition, we are performing biochemical analyses of the following proanthocyanidin genes from developing cranberry beans: leucoanthocyanidin reductase, anthocyanidin reductase and polyphenol oxidase, in order to determine their relative contribution to the seed coat darkening phenomenon of edible dry beans.

UNDERGRADUATE & GRADUATE STUDENTS

Currently accepting applications for undergraduate and graduate (M.Sc. and Ph.D.) positions.