Biochemistry and Molecular Biology of Fruit Development; Fruit and Vegetable Processing, Shelf life and Quality; Functional Foods, Nutraceuticals, and their Mechanism of Action.

Research Interests:

My research is primarily in the area of biochemistry, specifically pertaining to fruits and vegetables, and in relation to their senescence (ethylene, signal transduction, calcium second messenger system), shelf life and quality, nutraceutical ingredients and their mechanism of action. Recent research includes investigations on the role of phospholipase D (PLD) in membrane homeostasis and signal transduction. Structural and enzymological properties of recombinant PLD alpha will be investigated through site-directed mutagenesis of active- and regulatory-motifs, and its effect on various aspects of enzyme function. Technologies have been developed for enhancing the shelf life and quality of fruits, vegetables and flowers, based on the inhibition of PLD. Understanding the mechanism of action of food components in terms of disease prevention has become a major topic of my research. In this context, the biochemical mechanisms of action of grape/ wine polyphenols on cell growth and their importance in cancer prevention are being investigated using mammalian cell lines and athymic mouse model system. In total, my research is focussed on understanding the biochemical and molecular mechanisms of the developmental processes in fruits and vegetables and their role as functional foods in disease-prevention.

Hakimuddin, F., G. Paliyath and K. Meckling (2006) Treatment of MCF-7 breast cancer cells with a red grape wine polyphenol fraction results in disruption of calcium homeostasis and cell cycle arrest causing selective cytotoxicity. J. Agr. Food Chem., in press. The manuscript explores the relation between calmodulin-inhibitory properties of flavonoids as a mechanism that causes cytotoxicity in MCF-7 cells without affecting the viability of normal human mammary epithelial cells. The results show potential multi-site action of flavonoid components in calcium homeostasis which may also implicate the beneficial action of several flavonoid components in regulating physiological processes in humans (Role as PI, Support-Breast Cancer Soc.Canada, Food System biotech Centre).

Schofield, A. and G. Paliyath (2006) Modulation of carotenoid biosynthesis during tomato fruit ripening through phytochrome regulation of phytoene synthase activity. Plant Physiol. Biochem., 43, 1052-1060. Phytoene synthase (PSY) is a key enzyme in carotenoid biosynthesis. Increase in activity of PSY in response to a red light pulse does not appear to be regulated through gene expression, but potentially through protein phosphorylation (Role as PI, Support- NSERC-Industry).

Pinhero, R.G., K.C. Almquist, Z. Novotna and G. Paliyath (2003) Developmental regulation of phospholipase D in tomato fruits. Plant Physiol. Biochem., 41, 223-240. The role of phospholipase D in membrane deterioration during tomato fruit ripening has been examined in detail. Phospholipase D alpha was cloned from tomato (GenBank ACC # AF201661). Antisense suppression of phospholipase D during fruit development resulted in enhanced shelf life and quality, which shows that inhibition of phospholipase D could have beneficial effects in fruits and vegetables. The role of phospholipase D in the biochemical sequence of events triggered by ethylene, PLD expression patterns and subcellular localization by immunoelectron microscopy, are novel contributions in post harvest biology (Role as PI, Support-NSERC).

Paliyath,G., R.Y. Yada, D.P. Murr and R.G. Pinhero, (2003) Inhibition of phospholipase D (US Patent # 6, 514, 914) Hexanal and hexanol have been found to be efficient naturally occurring inhibitors of phospholipase D action. The inhibitory properties of hexanal is currently developed into a technology to delay senescence and enhance shelf life and quality of fruits, vegetables and partially processed products (Role as PI, Support-NSERC).

Rupasinghe, H.P.V., K.C. Almquist, G. Paliyath and D. P. Murr (2001) Cloning of hmg1 and hmg2 cDNAs encoding 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase (HMGR) and their expression and activity in relation to a-Farnesene synthesis in apple. Plant Physiol. Biochem., 39, 933-947. The relation between farnesene biosynthesis and superficial scald development in apples was studied by monitoring the expression and activities of HMG-CoA Reductase (HMG). A full-length cDNA encoding HMG1 (GenBank Acc.# AF315713) and a partial cDNA fragment encoding HMG2 (GenBank Acc.# AF316112) isoforms have been isolated. The expression of HMG1 is constitutive and that of HMG2 is responsive to developmental stages and ethylene. HMG2 expression increases in parallel with the accumulation of a- Farnesene in apples. This is the very first study of farnesene biosynthesis in apples (Role as PI, Support-NSERC).

Selected Publications:

Yuan, H., L. Chen, G. Paliyath, A. Sullivan, D.P. Murr and Z. Novotna. (2006). Immunohistochemical localization of phospholipase D in strawberry fruits. Scientia Horticulturae, 109, 35-42 (NSERC)

Yuan, H., L. Chen, G. Paliyath, A. Sullivan and D.P. Murr. (2006). Differential incorporation of a fluorescent phospholipid into strawberry fruit protoplast membrane in the presence of calcium and IAA. Physiol. Mol. Biol. Plant., 12, 35-42 (NSERC)

Yuan, H., L. Chen, G. Paliyath, A. Sullivan and D.P. Murr. (2005). Characterization of microsomal and mitochondrial phospholipase D activities and cloning of a phospholipase D alpha cDNA from strawberry fruits. Plant Physiol. Biochem., 43, 535-547 (NSERC)

Ahn, T., M. Oke, A. Schofield and G. Paliyath. (2005). Effect of Phosphorus Fertilizer Supplementation on Antioxidant Enzyme Activities in Tomato Fruits. J. Agric. Food Chem., 53, 1539-1545 (H.J. Heinz/Canadapt).

Oke, M., T. Ahn, A. Schofield and G. Paliyath. (2005). Effects of phosphorus fertilizer supplementation on processing quality and functional food ingredients in tomato. J. Agric. Food Chem., 53, 1531-1538 (H.J. Heinz/Canadapt).

Hakimuddin, F., G. Paliyath and K. Meckling. (2004). Selective cytotoxicity of a red grape wine flavonoid fraction against MCF-7 cells. Breast Canc. Res. Treatment, 85, 65-79.

Oke, M., R.G. Pinhero and G. Paliyath. (2003). The effects of genetic transformation of tomato with antisense phospholipase D cDNA on the quality characteristics of fruits and their processed products. Food Biotechnol., 17, 163-182 (OMAF).

Rupasinghe, H.P.V., G. Paliyath and D.P. Murr. (2003). Biosynthesis of isoprenoids in higher plants. Physiol. Mol. Biol. Plant., 9, 19-28 (OMAF).

Pinhero, R.G., G. Paliyath, T. Tanaka, R.Y. Yada and A. Marangoni. (2003). Partial purification and characterization of calmodulin-dependent NAD-kinase from potato leaves. Physiol. Mol. Biol. Plant., 9, 75-83 (NSERC).

Rupasinghe, H.P.V., K.C. Almquist, G. Paliyath, D.P. Murr, T.E. Elthon and A.C. Purvis. (2003). Involvement of the alternative oxidase in superficial scald in apple: Isolation and sequence analysis of the apple AOX1 cDNA. Acta Horticulturae (ISHS), 628, 481-486 (NSERC).

Whiting, M.D., H.P.V. Rupasinghe, D.P. Murr, G. Paliyath and D.D. Rowan. (2003). Effect of alpha-farnesene and its metabolites on membrane properties of “Delicious” apples. Acta Horticulturae (ISHS), 628, 627-633 (NSERC).

Ahn, T., A. Schofield and G. Paliyath. (2002). Changes in antioxidant enzyme activities during tomato fruit development. Physiol. Mol. Biol. Plant 8, 241-249 (Foragen).

Pinhero, R.G. and G.Paliyath. (2001). Antioxidant and calmodulin- inhibitory activities of phenolic components from fruit wines and their biotechnological implications. Food Biotechnol., 15, 179-192 (OMAF).

Rupasinghe, H.P.V., G. Paliyath and D. P. Murr. (2000). Partial purification and properties of a- Farnesene Synthase from apples. J. Amer. Soc. Hort. Sci., 125, 111-119 (NSERC).

Paliyath, G. and R.G. Pinhero. (2000). Seasonal variation in peroxidase activity of carnation flower petals in response to ethylene. Physiol. Mol. Biol. Plant., 6, 85-92 (Foragen).

Rupasinghe H.P.V., D.P. Murr, G. Paliyath and J.R. DeEll. (2000). Suppression of a-farnesene synthesis in ‘Delicious’ apples by aminoethoxyvinylglycine (AVG) and 1-methylcyclopropene (1-MCP), Physiol. Mol. Biol. Plant 6, 195-198 (OMAF).

For a complete list of Research Contributions and publications please visit:
http://www.plant.uoguelph.ca/faculty/gpaliyath/publications.html