Poster: Plant Insect/Nematode Interactions

Abs # 680: Discovery of an insect enzyme insensitive to proteinase inhibitors (PIs) and a proposed mechanism for resistance to PIs

Presenter:	Dunse, Kerryn M, k.dunse@latrobe.edu.au
Authors	Dunse, Kerryn M (A)   Korscinsky, Michael  (B)   Craik, David  (B)   Anderson, Marilyn  (A)
Affiliations:	(A): Department of Biochemistry, La Trobe University (B): Institute for Molecular Bioscience, University of Queensland

Floral tissues and wounded leaves of the ornamental tobacco, Nicotiana alata, produce copious amounts of small (6kDa) serine proteinase inhibitors (NaPIs) that inactivate the major digestive enzymes in several insect pests. These inhibitors are derived from a precursor protein that contains six contiguous PIs that are cleaved into two chymotrypsin inhibitors (C1+C2) and four trypsin inhibitors (T1-T4). These inhibitors retard growth and development in Helicoverpa species when incorporated into artificial diets or transgenic plants. Generally, the larvae respond to consumption of NaPI by altering the complement of enzymes in gut and induction of PI resistant enzymes.

Here we report on the isolation and cloning of an NaPI-resistant enzyme, and the use of structural homology modelling to propose a mechanism for its low binding affinity towards NaPIs.