Cellular and molecular mechanisms of ion transport by the insect excretory system

昆虫是最丰富的动物群体，约占已知动物物种的95%。虽然昆虫似乎在热带地区最丰富，但它们已经成功地利用了陆地环境的几乎每一个生态位，包括一些导致重大经济、农业或健康危机的生态位。为了应对这些不同生态位施加的大量环境压力，昆虫已经进化出复杂的系统来控制渗透和离子平衡，使大多数物种能够在一个狭窄的范围内调节它们的血淋巴组成和体积。昆虫调节自身渗透状态的进化适应性让研究人员困惑了几十年。通过我的研究，我将进一步了解昆虫的渗透调节和排泄，以及这一群体进化出的巨大多样性。在目前的拨款提案中，我们研究了恰加斯病的载体——长角锥蝽的渗透调节。每一餐血都给长尾瓢虫带来了过量的水和NaCl，造成了严重的渗透胁迫，昆虫通过大量的利尿过程来解决这个问题。利尿是由排泄系统（马氏小管和肾小管）完成的，它通过活跃的离子运输和渗透性的水流形成尿液。利尿激素刺激作物和马氏小管以非常高的速率运输离子。完全受刺激的小管以相当于每个细胞每10秒交换其全部体积的速率运输液体，并在5秒内交换其细胞内Na+和Cl-含量。这需要高效的调节机制来确保餐后利尿过程中离子和液体的平衡。在我的指导下，HQP将在本科生、研究生和博士后水平上研究协调作物和马尔比氏小管功能的激素信号，以及维持体内平衡所需的细胞内机制。此外，我的研究项目将促进我们对上皮生理学基本机制的理解。上皮生理学中最有趣的问题之一是细胞内串扰机制的性质，该机制调节离子转运体以维持跨上皮运输，同时保护细胞质成分。昆虫排泄上皮是研究这些机制的理想模型，但迄今为止这些机制仍然难以捉摸。通过这项研究产生的知识将有助于改善加拿大人的生活，促进合理制定具有成本效益、针对特定昆虫和无害环境的虫害防治措施，并提供可能有助于更好地了解健康状况的新知识。这笔资金将用于支持HQP在分子生物学、高级电生理学和药理学方面的培训，为他们在学术界和工业界的职业生涯做好准备。

Insects are the most abundant animal group, representing roughly 95% of the known animal species. Although insects appear to be most abundant in the tropics, they have successfully exploited almost every ecological niche of the terrestrial environment including some that lead to major economic, agricultural, or health crisis. In order to deal with the vast number of environmental stresses that these various ecological niches have imposed, insects have evolved sophisticated systems for the control of osmotic and ionic balance that allow most species to regulate their haemolymph composition and volume within a narrow range. The amazing evolutionary adaptations that allow insect to regulate their osmotic state have puzzled researchers for decades. Through my research I will further our understanding of osmoregulation and excretion in insects and the enormous diversity that this group has evolved. In the current grant proposal, we study osmoregulation in the triatomine bloodsucker Rhodnius prolixus, a vector for Chagas disease. Each blood meal loads R. prolixus with excess water and NaCl imposing severe osmotic stress, which the insect resolves with a massive diuretic process. Diuresis is carried out by the excretory system-the Malpighian tubules and crop-which forms urine by active ion transport and osmotically obliged water flow. Diuretic hormones stimulate both the crop and the Malpighian tubules to transport of ions at very high rates. Fully stimulated tubules transport fluid at rates equivalent to each cell exchanging their whole volume every 10 s and their intracellular Na+ and Cl- content in 5 s. This requires highly efficient regulatory mechanisms to ensure ion and fluid homeostasis during postprandial diuresis. In this grant HQP under my supervision at the undergraduate, graduate, and postdoctoral levels will study the hormonal signals that coordinate the function of the crop and Malpighian tubules and the intracellular machinery needed to preserve homeostasis. In addition, my research project will advance our understanding of fundamental mechanisms of epithelial physiology. One of the most interesting questions on epithelial physiology is the nature of the intracellular crosstalk mechanisms which regulate ion transporters to maintain transepithelial transport while defending cytosolic composition. Insect excretory epithelia are ideal models to study these mechanisms, that have remain elusive so far. The knowledge generated through this research will contribute to improve the life of Canadians by facilitating the rational development of cost-effective, insect specific and environmentally benign pest control measures and by providing new knowledge that may help better understand health conditions. Funding from this grant will support the training of HQP on molecular biology, advanced electrophysiology and pharmacology that will prepare them for careers in academia and in industry.