Science, Technology and Engineering

Research Fellow

Department of Biochemistry

Characterisation of lepidoteran serine proteinases

Dr Kerry Dunse BSc(Hons) (Melb), PhD (La Trobe) Research Fellow, Anderson lab Group leader (Insect Protection), Hexima Ltd Phone: +61 3 9479 1156 (Lab), +61 3 9479 3926 (Office) Fax: +61 3 9479 1266 Email: K.Dunse@latrobe.edu.au Room 380 (Lab), Room 357 (Office), Physical Sciences 4

Research

Helicoverpa punctigera chymotrypsin (red) in complex with the chymotypsin inhibitor from Nicotiana alata (blue)

Lepidopteran insects are major pests of important agricultural crops worldwide, and have developed resistance to many of the conventional chemical controls. We are investigating the potential of a series of proteinase inhibitors isolated from the ornamental tobacco, Nicotiana alata (NaPI), to enhance insect resistance in cotton plants against the Lepidopterans, Helicoverpa armigera and H. punctigera.

My work is directed at characterizing the large and diverse family of chymotrypsins and their interaction with NaPI. I have purified, cloned and constructed molecular models of a new chymotrypsin which is resistant to inhibition by NaPI. Using mutagenesis and baculovirus expression we aim to solve the structure of the first Lepidopteran chymotrypsin and determine the molecular basis of PI-resistance.

Another aspect of my work is to identify inhibitors that abolish the activity of the NaPI resistant proteases. To do this I have constructed a phage display library of variant NaPIs to select new inhibitors that target the NaPI-resistant proteases. The presence of multiple PI domains in a single gene allows the substitution of individual domains with these novel inhibitors to target multiple proteases in the insect gut.

Lepidopteran chymotrypsins are interesting enzymes due to several unique features that distinguish them from their mammalian counterparts. These differences have posed several interesting evolutionary questions and will also aid the design of insect-specific proteinase inhibitors.

Publications

Dunse, K.M., Kaas, Q., Guarino, R.F., Barton, P.A., Craik, D.J., Anderson, M.A. (2010) Molecular basis for the resistance of an insect chymotrypsin to a potato type II proteinase inhibitor. Proc Natl Acad Sci U S A. 107: 15016-21

Dunse, K.M., Stevens, J.A., Lay, F.T., Gaspar, Y.M., Heath, R.L., Anderson, M.A. (2010) Coexpression of potato type I and II proteinase inhibitors gives cotton plants protection against insect damage in the field. Proc Natl Acad Sci U S A. 107: 15011-5

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