Grant: Discovery Grants Program - Individual

Embryos of the crustacean, Artemia franciscana , develop into swimming larvae or they encyst and enter diapause, a physiological state characterized by developmental arrest and greatly reduced metabolism. Encysted embryos (cysts)arevery stress tolerant, survivingextreme temperature, desiccation and years without oxygen when hydrated at ambient temperature. A. franciscana cysts thereforerepresent one of the most stresstolerantmulticellular life forms on Earth. A. franciscana embryos exhibit differential gene regulation during diapause-destined development, producingproteins required for the initiation,maintenance and termination of diapause, with maintenance the period of greatest stress tolerance. The global objectives of the proposed research are to elucidate cell, molecular and biochemical mechanisms by which A. franciscana regulate diapause-specific development and determine how embryos survive severephysiological stress. Heat shock factor 1 (HSF1)whichnormally activates genesexpressed during physiological stress will be tested to determine ifit regulates gene expression during diapause. Of particular interestis anabundant, diapause-specificmolecular chaperone, p26, which functions in the absence of an energysupply. p26 is thought to bind denaturing proteinsin diapause embryos and protect them from irreversible denaturation. Consequently, substrate proteins of p26 will be identified. Several molecular chaperones such as Hsp40, Hsp70 and Hsp90 require energy for activity. The synthesis ofthese proteins will be investigated duringdiapause-destined embryo development,as will their protectivefunction when energy is limiting, as occursin diapause. Proteins that regulate diapause termination will also be identified. Thus, a central question addressed by the proposed research is how embryos of A. franciscana survive severe stressors which kill most other organisms ratherquickly. Are molecular chaperones responsible for stress tolerance and, if so, how do they contribute tothis process? Answering these questions will provide significant fundamental insights into diapause and the functions of essential cellular proteins such as themolecular chaperones. On an applied level, the proposed research mayfacilitate the use of A. franciscana in aquaculture where the organism is usedto feed the larvae of commercially important fish and aquatic invertebrates. Hsp70, for example, plays a role in the resistance of A. franciscana to bacterial infection, indicating that the proposed work will lead to improvements in the culture of A. franciscana .Moreover, a better understanding of diapause has consequences for agriculture, forestry and medicine as it may allow for the development of methods for the control of insect pestsable to survivewinter and attempts at their eradication when in diapause, this of direct benefit to Canada.