Diapause, Stress Tolerance and Molecular Chaperones in Artemia franciscana

甲壳动物卤虫的胚胎发育成游泳的幼虫，或者它们包囊并进入滞育，滞育是一种以发育停滞和代谢大大减少为特征的生理状态。包囊胚胎（包囊）非常耐胁迫，在环境温度下水合时可以在极端温度，干燥和无氧的情况下存活多年。A.因此，弗朗西斯卡纳孢囊代表了地球上最耐压力的多细胞生命形式之一。A. franciscana胚胎在滞育发育过程中表现出不同的基因调控，产生滞育的起始、维持和终止所需的蛋白质，其中维持期是最大的胁迫耐受期。该研究的总体目标是阐明A. franciscana调节滞育特异性发育，并决定胚胎如何在严重的生理应激下存活。热休克因子1（HSF 1），通常激活基因表达的生理压力期间将进行测试，以确定它是否调节基因表达滞育期间。特别令人感兴趣的是一个丰富的，滞育特异性分子伴侣，p26，它的功能在缺乏能量供应。p26被认为与滞育胚胎中的变性蛋白结合，并保护它们免受不可逆变性。因此，p26的底物蛋白将被鉴定。几种分子伴侣如Hsp40、Hsp70和Hsp90需要能量来进行活性。这些蛋白质的合成将在滞育胚胎发育过程中进行研究，当能量有限时，它们的保护功能也会发生在滞育中。还将鉴定调节滞育终止的蛋白质。因此，这项研究提出的一个中心问题是A.弗朗西斯卡纳在严重的压力下存活下来，而这些压力会很快杀死大多数其他生物。分子伴侣是否负责胁迫耐受性，如果是的话，它们是如何参与这一过程的？这些问题的解决将为滞育和分子伴侣等重要细胞蛋白的功能提供重要的基础性见解。在应用层面上，拟议的研究可能会促进A。franciscana在水产养殖中，该生物体用于喂养商业上重要的鱼类和水生无脊椎动物的幼虫。例如，Hsp70在A. franciscana对细菌感染的敏感性，表明所提出的工作将导致A.弗兰西斯卡纳。此外，更好地了解滞育对农业、林业和医学也有影响，因为它可能有助于制定控制能够越冬的害虫的方法，并试图在滞育期间消灭这些害虫，这对加拿大有直接的好处。

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) are very stress tolerant, surviving extreme temperature, desiccation and years without oxygen when hydrated at ambient temperature. A. franciscana cysts therefore represent one of the most stress tolerant multicellular life forms on Earth. A. franciscana embryos exhibit differential gene regulation during diapause-destined development, producing proteins 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 severe physiological stress. Heat shock factor 1 (HSF1) which normally activates genes expressed during physiological stress will be tested to determine if it regulates gene expression during diapause. Of particular interest is an abundant, diapause-specific molecular chaperone, p26, which functions in the absence of an energy supply. p26 is thought to bind denaturing proteins in 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 of these proteins will be investigated during diapause-destined embryo development, as will their protective function when energy is limiting, as occurs in 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 rather quickly. Are molecular chaperones responsible for stress tolerance and, if so, how do they contribute to this process? Answering these questions will provide significant fundamental insights into diapause and the functions of essential cellular proteins such as the molecular chaperones. On an applied level, the proposed research may facilitate the use of A. franciscana in aquaculture where the organism is used to 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 pests able to survive winter and attempts at their eradication when in diapause, this of direct benefit to Canada.