Postharvest biochemistry, Secondary metabolism

Research Interests:

   Postharvest Biochemistry

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 controlled atmosphere (CA) storage. CA storage is a postharvest management technology designed to limit respiration and ethylene-mediated processes leading to the loss of fruit quality, and also serves to maintain the freshness and 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. Currently, my lab is 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 fruit during CA-storage are unknown. To address this, we are conducting studies to determine whether an imbalance in whole fruit redox metabolites (i.e. ascorbate, glutathione, and pyridine dinucleotides) 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 phenylproapnoid 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.

   Evidence for Flavonol Catabolism in Plants

My laboratory is investigating the key biochemical and molecular determinants promoting the loss of flavonols, specifically quercetin diglycosides in vegetative plant tissues of Arabidopsis thaliana. These diglycosides 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 quercetin diglycosides, as well as the enzymes promoting their loss in Arabidopsis are scantly described. We are using biochemical analyses together with functional genomics to elucidate the major enzymatic steps required for the degradation of stress-inducible quercetin diglycosides.

   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.

Recent Publications:

Roepke, J., T. Jean, K.J. Perkel, T. Blom and G.G. Bozzo. (2012) Daminozide alters anthocyanin metabolism in ray florets of bronze chrysanthemum (Chrysanthemum morifolium Ramat.). Submitted to Journal of Plant Growth Regulation.

Shelp, B.J., G.G. Bozzo, A. Zarei, J.P. Simpson, C.P. Trobacher and W.L. Allan. (2012) Strategies and tools for studying the metabolism and function of γ-aminobutyrate in plants: II. Integrated analysis. Botany (in press).

Shelp, B.J., G.G. Bozzo, C.P. Trobacher, G. Chiu, and V.S. Bajwa. (2012) Strategies and tools for studying the metabolism and function of γ-aminobutyrate in plants. I. Pathway structure. Botany (in press).

Shelp, B.J., G.G. Bozzo, C.P. Trobacher, A. Zarei, K.L. Deyman and C. J. Brikis. (2012) Hypothesis/review: Contribution of putrescine to 4-aminobutyrate (GABA) production in response to abiotic stress. Plant Science 193-194: 130-135.

Brauer, E.K., A. Rochon, Y.M. Bi, G.G. Bozzo, S.J. Rothstein and B.J. Shelp. (2011) Reappraisal of nitrogen use efficiency in rice overexpressing glutamine synthetase1. Physiologia Plantarum 141: 361-372.

Eudes, A., G.G. Bozzo, J.C. Waller, V. Naponelli, E.-K. Lim, D.J. Bowles, J.F. Gregory 3rd and A.D. Hanson. (2008) Metabolism of the Folate Precursor p-Aminobenzoate in Plants: Glucose Ester Formation and Vacuolar Storage. Journal of Biological Chemistry 283: 15451-15459.

Bozzo, G.G., G.J. Basset, V. Naponelli, A. Noiriel, J.F. Gregory 3rd and A.D. Hanson. (2008) Characterization of the Folate Salvage Enzyme p-Aminobenzoylglutamate Hydrolase in Plants. Phytochemistry 69: 29-37.

Orsomando, G., G.G. Bozzo, R.D. de la Garza, G.J. Basset, E.P. Quinlivan, V. Naponelli, F. Rébeillé, S. Ravanel, J.F. Gregory 3rd and A.D. Hanson. (2006) Evidence for Folate-Salvage Reactions in Plants. Plant Journal 46: 426-435.

Bozzo, G.G., E.L. Dunn and W.C. Plaxton. (2006) Differential Synthesis of Phosphate-Starvation Inducible Purple Acid Phosphatase Isozymes in Tomato (Lycopersicon esculentum) Suspension Cells and Seedlings. Plant Cell & Environment 29: 303-313.

Klaus, S.M., E.R. Kunji, G.G. Bozzo, A. Noiriel, R.D. de la Garza, G.J. Basset, S. Ravanel, F. Rébeillé, J.F. Gregory 3rd and A.D. Hanson. (2005) Higher Plant Plastids and Cyanobacteria have Folate Carriers Related to those of Trypanosomatids. Journal of Biological Chemistry 280: 38457-38463.