Philip J. Dix, BSc, PhD, (Leicester) EurBiol
Head of Laboratory

Plant Cell Biology

• Professor Philip J. Dix
• Tel: (353-1) 708 3836; Fax: (353-1) 708 3845
• phil.dix@nuim.ie
• Institute of Bioengineering & Agroecology
• The Plastid Factory
• The Marie Curie Laboratory for Membrane Proteins

Head of Laboratory

Philip J. Dix, BSc, PhD, (Leicester) EurBiol

Research Interests

The research in this group is directed to the in vitro genetic manipulation of plants through genetic transformation. The objectives are both fundamental and applied. The generation and molecular characterisation of antibiotic resistant mutants of Solanaceous plants has led to several chloroplast genetic markers which are being used for studies on segregation and recombination in chloroplast genomes, as well as functional analysis of the genes. They also provide the basis for a novel chloroplast transformation procedure developed at Maynooth. This fundamental research is carried out with tobacco (a model species), but through EU-funded projects we are extending the plastid transformation work to include other crop species, including Brassica crops (cauliflower, broccoli, oilseed rape), and to explore agriculturally useful traits, including insect and herbicide resistance, phytoremediation, and (in collaboration with J. Nugent) oral vaccine production.

Another major area of investigation is the regulation of peroxidase genes, the targeting of the gene product and its role in plant development and stress tolerance. Tobacco plants over-expressing peroxidases in the cell wall (apoplast) or cytoplasm, sometimes in combination with other oxidative enzymes (oxalate oxidase), are being evaluated for changes in such developmental features as xylem production, and in resistance to abiotic (UV, temperature, high light, ozone) and biotic (insects, pathogens) stresses.

An applied research area is the improvement in shelf life and quality of vegetable crops. Cauliflower plants expressing genes for cytokinin metabolism, under control of a senescence-associated promoter showed delayed leaf ageing, and changes in nitrogen metabolism are being studied in plants expressing a bacterial asparagine synthetase gene. The role of cytokinins in development is also being explored in transgenic apple trees.

The group is experienced in a range of methods for the genetic transformation of plants, including biolistics, the shooting of DNA-coated tungsten particles directly into the plant cells.

Laboratory Personnel

Post-Doctoral Fellows

• Manfred Klaas, DipBiol, PhD (Kiel)
• Peter Medgyesy, BSc, PhD (Szeged)
• Julia Hinderberger, DipChem, PhD (Marburg)

Postgraduate Students

• Benedicte Le Martret
• Rob Van Den Bekerom

Technical Assistant (part time)

• Aine Butler

Funding Sources

EU, Enterprise Ireland, Science Foundation Ireland, Teagasc, Departmental funding

Selected Publications

• Dix, P.J.: The role of mutant cell lines in studies on environmental stress tolerance: an assessment. The Plant Journal 3 , 309-313 (1993).
• O'Neill, C.M., Horváth, G.V., Horváth, E., Dix, P.J. and Medgyesy, P.: Chloroplast transformation in plants: polyethylene glycol (PEG) treatment of protoplasts is an alternative to biolistic delivery systems. The Plant Journal 3 , 729-738 (1993).
• Kavanagh, T.A., O'Driscoll, K.M., McCabe, P.F. and Dix, P.J.: Mutations conferring lincomycin, spectinomycin, and streptomycin resistance in Solanum nigrum are located in three different chloroplast genes. Molecular and General Genetics 242 , 675-680 (1994).
• Dix, P.J. and Kavanagh, T.A.: Transforming the plastome: Genetic markers and DNA delivery systems. Euphytica 85 , 29-34 (1995).
• Deane, C.R., Dix, P.J. and Fuller, M.P.: Selection of hydroxyproline resistant proline accumulating mutants of cauliflower for improved frost resistance. Acta Horticulturae 407 , 123-129 (1996).
• Kavanagh, T.A., Thanh, N.D., Lao, T.N., McGrath, N.,Peter, S.O., Horváth, E.M., Dix, P.J. and Medgyesy, P.: Nicotiana plastid transformation by Solanum plastid DNA is efficient due to multiple recombination events. Genetics 132 , 1111-1122 (1999)
• Kis, M., Burbridge, E., Brock, I.W., Heggie, L., Dix, P.J. and Kavangh, T.A.: An N-terminal peptide extension results in efficient expression, but not secretion, of a synthetic horseradish peroxidase gene in transgenic tobacco. Annals of Botany 93 , 303-310 (2004)
• Jansen, M.A.K., Elfstrand, M., Heggie, L., Sitbon, F., Dix, P.J. and Thorneley, R.N.F.: Over-expression of phenol-oxidising peroxidases alters the UV-susceptibility of transgenic Nicotiana tabacum. New Phytologist 163 , 585-594 (2004)
• Nugent, G.D., ten Have, M., van der Gulik, A., Dix, P.J., Uijtewaal, B.A. and Mordhorst, A.P.: Plastid transformants in tomato selected using mutations affecting ribosome structure. Plant Cell Reports 24 , 341-349 (2005)
• Nguyen, T.T., Nugent, G.D., Cardi, T. and Dix, P.J.: Generation of homoplasmic plastid transformants of a commercial cultivar of potato (Solanum tuberosum L.). Plant Science 168 , 1,495-1,500 (2005)
• Altpeter, F., Baisakh,N., Beachy, R., Bock, R., Capell, T., Christou, P., Daniell, H., Datta, K., Datta, S., Dix, P.J., Fauquet, C., Huang, N., Kohli, A., Mooibroek, H., Nicholson, L., Nguyen, T.T., Nugent, G., Raemakers, K., Romano, A., Somers, D.A., Stoger, E., Taylor N. and Visser. R.: Particle bombardment and the genetic enhancement of crops: myths and realities. Molecular Breeding 15 , 305-327 (2005)
• Ma, J.K.-C., Barros, E., Bock, R., Christou, P., Dale, P.J., Dix, P.J., Fischer, R., Irwin, J., Mahoney, R., Pezzotti, M., Schillberg, S., Sparrow P. and Twyman, R.M.: The production of pharmaceutical proteins in transgenic plants – current perspectives. EMBO Reports 6, 593-599 (2005)
• Craig, W., Gargano, D., Scotti, N., Nguyen, T.T., Lao, N.T., Kavanagh T.A., Dix P.J. and Cardi. T. Direct gene transfer in potato: a comparison of particle bombardment of leaf explants and PEG-mediated transformation of protoplasts. Plant Cell Reports 24, 603-611 (2005)
• Heggie, L., Jansen, M.A.K., Burbridge, E.M., Kavanagh, T.A., Thorneley, R.N.F. and Dix, P.J.: Transgenic tobacco (Nicotiana tabacum L. cv. Samsun-NN) plants over-expressing a synthetic HRP-C gene are altered in growth, development and susceptibility to abiotic stress. Plant Physiology and Biochemistry  43, 1067-1073 (2005)
• Nugent, G.D., Coyne, S., Nguyen, T.T., Kavanagh T.A. and Dix, P.J.: Nuclear and plastid transformation of Brassica oleracea var. botrytis (cauliflower) using PEG-mediated uptake of DNA into protoplasts. Plant Science 170, 135-142 (2006)
• Burbridge, E., Diamond, M., Dix, P.J. and McCabe, P.F.: Use of cell morphology to evaluate the effect of a peroxidase gene on cell death induction thresholds in tobacco. Plant Science 171, 138-146 (2006)
• Nguyen, K.-H., Jordi, W., Van Dun, K., Schepers, F., Davelaar, E., Stoopen, G., Dix, P.J. and Kane, E.J.: Delayed senescence in cauliflower transformed with an autoregulated isopentenyl transferase gene. International Journal of Plant Science 169, 339-347 (2008)
• Craig, W., Lenzi, P., Scotti, N., De Palma, M., Saggese, P., Carbone, V., Mcgrath Curran, N., Magee, A.M., Medgyesy, P., Kavanagh, T.A., Dix, P.J., Grillo, S. and Cardi, T.: Transplastomic tobacco plants expressing a fatty acid desaturase gene exhibit altered fatty acid profiles and improved cold tolerance. Transgenic Research 17, 769-782 (2008)
• McCabe, M.S., Klaas, M, Gonzalez-Rabade, N., Poage, M., Badillo-Corona, J., Zhou, F., Karcher, D., Bock, R., Gray, J.C. and Dix, P.J.: Plastid transformation of high biomass tobacco variety Maryland Mammoth for production of HIV-1 p24 antigen. Plant Biotechnology Journal (in press) Published Online: Sep 2 2008 DOI: 10.1111/j.1467-7652.2008.00365.
• Chikkala, V.R.N., Nugent, G.D., Dix, P.J. and Stevenson, T.W.: Regeneration from leaf explants and protoplasts of Brassica oleracea var. botrytis (cauliflower). Scientia Horticulturae (in press).
  

Last edited: Wednesday, 13-May-2009 10:27:23 IST

Biology Department , NUI Maynooth
Tel: +353-1-708 3843 | Fax: +353-1-708 3845| Email: terry.roche@nuim.ie