In 1931, Mungomery stated "whitegrubs have been for years past, and still are, the worst insect problem confronting the sugar industry". This statement remains true to this day, with canegrubs costing the Australian sugar industry A$7.22 million in lost production and in use of insecticides. The development of a sugarcane cultivar with resistance to canegrub attack would be a valuable addition to the recently implemented canegrub management program. This thesis examined the possibility that natural inhibitors derived from canegrubs could be incorporated in sugarcane to reduce or prevent its destruction by canegrubs. The research described here demonstrated that canegrub haemolymph contains inhibitors with activity against commercially purified enzymes and serine proteases found in crude midgut extracts. A cDNA encoding a potential canegrub protease inhibitor (DA10 12) belonging to the Ascaris family was cloned, but it did not have activity against the major canegrub midgut proteases. This protein does, however, still have potential for modification into a serine protease inhibitor suitable for use as a novel insect resistance transgene. The possibility of using haemolymph derived inhibitors as novel antimetabolites in a canegrub management strategy based on transgenic plants was also explored. The findings suggest that proteins with properties similar to those of DA10 12 will require the presence of a signal peptide and/or codon optimisation for successful expression in sugarcane. The research outlined in this thesis is the first investigation of protease inhibitors in the haemolymph of scarab larvae, and is the first report of an Ascaris family inhibitor that does not inhibit a serine protease.
| Identifer | oai:union.ndltd.org:ADTP/265124 |
| Date | January 2005 |
| Creators | Nutt, Kerry Anne |
| Publisher | Queensland University of Technology |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
| Rights | Copyright Kerry Anne Nutt |
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