Introduction 

The use of proteinase inhibitors to engineer plants for resistance to a wide range of insect pests has recently gained much attention. Several studies have demonstrated effectiveness in the use of such inhibitor genes for transgenic control of various pests including insects and nematodes.  Proteinase inhibitors that operate by inhibiting the gut enzymes that break down proteins in the insect’s diet have been isolated in several plant species and are believed to function as defense compounds against insect and pathogen attack. Exploring plants own defense mechanisms, by engineering and the introduction of insect defense proteins from other plants is seen as a more natural strategy. Several genes encoding various proteinase inhibitors have been introduced into crop plants with successful improvement in resistance to pests and these plants are now at various stages of field-testing worldwide. The project is in collaboration with Rothamsted Research, UK and Laval University Quebec, Canada.

General Project  Objectives

1. Evaluate a strategy for the use of cysteine proteinase inhibitors (cystatins) as a first target gene for genetic engineering of banana for resistance to banana weevil.

2. To optimise through protein engineering, inhibition activity of at least two plant cystatins to obtain novel inhibitors with increased activity against banana weevils and thus acquire intellectual property rights.

Specific Objectives

1. Characterise proteolytic enzyme activity in the mid-gut of banana weevils and thus identify potential proteinase inhibitors of plant origin.

2. Develop in-vitro and in-vivo bio-assays for testing purified cysteine proteinase inhibitors against gut proteinase activity, and on larval growth and development.

3. Engineer through site-directed mutagenesis and bio-informatics tools, at least two plant cystatins with improved and specific inhibition of banana weevil gut proteinase enzymes, both in-vivo and in-vitro.

4. Design gene constructs for engineering bananas with novel cysteine proteinase inhibitor genes.

Collaborators

Karl Kunert, National Banana Research Programme, KARI/NARO, Uganda

Altus Viljoen, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria South Africa.

Michael Pillay and Cliff Gold, International Institute of Tropical Agriculture, East and Southern Africa Regional Center, P. O. Box 7878, Kampala, Uganda.