1. Natural products as an alternative of chemical pesticides
The use of organic synthetic pesticide has made significant improvements in agricultural production. However, its effect on the environment and human health has also posed a serious problem. ?For the sake of environmental safety and human health, the necessity of more friendly control strategy is more apparent in the recent years, especially focused on natural product alternatives for pest control in developing countries.? Natural products from Djulis (Chenopodium formosaneum, a traditional food sources used by the aboriginal people) and Coleus amboinicus is currently being investigated in our laboratory.? These studies aim to counteract the synthetic pesticide-posed problems by using natural product as an alternative strategy for pest control.? The results indicated that both plants are effective against mosquito and several agricultural pests.? Further identification of active insecticidal ingredient from both plants by using HPLC and GC/MS are currently undergo in our laboratory.
2. Reproductive mechanism of autogenous mosquitos
Most of adult female take blood meals for egg development, either as an absolute (anautogenous) or facultative (autogenous) requirement.? The mechanism of reproduction in autogenous remind to be illustrated.? The mosquito of Culex pipiens molestus is a facultative autogenous mosquito that do not take any blood meal in the adult stage.? Our laboratory have studied the differential expression of proteins in between anautogenous and facultative mosquitoes during the first gonotrophic cycle by using proteomic techniques.? This studies aim to understand the mechanism of blood meal independent signal for egg development in Cx. p. molestus.?
3. Development of a chitin-targeted bio-insecticide
The use of organic synthetic pesticide has made significant improvements in agricultural production. However, its effect on the environment and human health has also posed a serious problem. To counteract these problems an alternative approach to using chemical pesticides is currently being investigated.
Chitin is one of the most abundant amino biopolymer found in nature and it has the potential to be utilised as an alternative source of organic pesticides. It makes up the structural elements of the exoskeletons and peritrophic membranes in various insects. The peritrophic membrane is the first tissue that comes into contact with ingested food. Chitin is not found in vertebrates and plants, and as such, its metabolism constitutes a potential target for selective bio-insecticidal use in controlling fungi-borne diseases and insect pests. Thus it is the aim of the current project to develop a chitin-targeted bioinsecticde. In order to develop this bioinsecticide, the chitinase gene will be cloned from two important pests (such as Plutella xylostella and Spodoptera litura) to over-express in E. coli.in the first year.? The over-expressed chitinase will be further purified and characterized, including its insecticidal activity,chitin-binding activity and stability. There are at least three prominent features of the chitin-targeted bio-insecticide. Firstly, chitin-targeted bio-insecticide is not toxic to humans since chitin does not exist in human tissues. Secondly, it is a proteinaceous bio-insecticide that is bio-gradable in nature. Third, it is a broad-spectrum bio-insecticide since its action is targeted at chitin, a component of all insects. The long-term goal of this proposal also aims to explore the potential of chitinase gene as a bio-insecticide in transgenic plants.
4. Proteomic identification of peritrophic membrane proteins as a potential target for insect control
5. Explore the biomedical application of Gal-1 and chitosan
Peritrophic membrane (PM) is a non-cellular film that lines the digestive tract of most insects to surrounding the ingested food bolus.? The PM moves poesteriorly with the food bolus along the digestive canal, and eventually excretes in accompany with larval fecal pellets.? Therefore, insects invest a significant amount of energy and resource to produce and maintain the PM.? The PM is composed of chitin and proteins and plays important roles in facilitating food digestion and providing protection to the gut epithelium.? The important physiological functions of PM suggest that PM can be a significant structural target for insect control.? Plutella xylostella, with its high reproductive potential, short generation time and characteristics adaptive to adverse envrionemts, has become one of the most serious pest of cruciferous plants worldwide, however, there is no information available regarding its PM formation and molecular structure.? The purpose of this project is to dissect the ultrastructure of PM and to systematic identification of PM proteins by proteomic approach in P. xylostella.? These projects aim to study of PM as a potential target for diamondback moth (P. xylostella) control.? According to this study, we can directly unravel the structure and composition of PM in P. xylostella.? The information obtained from this study is essential for developing methods for targeting the PM by various mechanisms.
Chitin and chitosan are two derivatives of the exoskeletons of insects and shells of crustaceans and could also found in the cell walls of some fungi such as Mucor rouxii.? Chitin and chitosan could achieve hemostasis and allow the promotion of normal tissue regeneration.? Besides, the biodegradable chitin or chitosan itself provided bacteriostatic and fungistatic activities.? Therefore, chitin and chitosan have been one of the important materials for biomedical applications.? Although chitin and chitosan membrane have been shown the advantage of biocompatibility in supporting of cell immobilization, some cell types including 3T3 and KB cells are unable to attach and grow on chitosan membrane.? Our current studies show that the expression of Gal-1 (a £]-galactoside binding protein involved in cell proliferation and apoptosis) could enhance the attachment and proliferation of 3T3 (Biomaterials, in press, please see the attached paper) and IRC (immortal rat chondrocyte) (unpublished result) cells on chitosan membrane.? These results provide the basis for the understanding of the mechanism of cell growth on tissue-engineered chitosan membrane