The ionoregulatory mechanisms of insect chill tolerance

昆虫耐冷性的离子调节机制

• 批准号: RGPIN-2018-05322
• 负责人: MacMillan, Heath
• 金额: $ 2.48万
• 依托单位: Carleton University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=658345
• 关键词: ionoregulatory; mechanisms; insect; chill; tolerance

My long-term goal is to develop an integrative understanding of how temperature sets limits to animal performance, and I will begin with a focus on chill tolerance. The majority of insects are chill-susceptible, meaning they suffer non-freezing injury at relatively mild low temperatures. A primary consequence of cold exposure for these insects is a disruption of ion and water homeostasis; a cold-induced rise in extracellular [K+] depolarizes cells, causing injury and death. Through thermal adaptation or plasticity, however, insects can better maintain ion homeostasis in the cold, and thereby avoid injury. Thus, modifications to the physiology of ionoregulatory organs likely underlie variation in insect chill tolerance. ******Insect ion balance is maintained by the coordinated transport properties of the Malpighian tubules (MT) and gut. These organs are highly relevant to chill tolerance, but the mechanisms by which chilling impairs their function are unknown. In my first grant cycle I propose to use fruit flies, locusts, and crickets to examine: 1) the effects of chilling on the transport physiology of the ionoregulatory organs, 2) the effects of chilling on paracellular epithelial barriers, and 3) endocrine control of chill tolerance.******In my first objective, the migratory locust will be used to examine how temperature directly impacts transcellular ion transport in the MT and gut epithelia. To accomplish this, I will use a variety of techniques to examine temperature effects on ion and water transport, and quantify the relative contributions of individual transporters to maintaining ion balance in the cold. These techniques will then be adapted to cricket species that vary in chill tolerance to examine epithelial thermal adaptation.******Molecules can cross epithelia through not only transcellular, but also paracellular routes, the tightness of which are mediated by the septate junctions (SJ). In my second objective, I will determine the role of SJs and their component proteins in Drosophila chill tolerance. I will begin by examining how thermal acclimation modulates gut barrier properties and tissue-specific expression patterns of SJ proteins in Drosophila. In parallel, I will use locusts to determine whether cold-induced SJ disruption is a common challenged faced by insects, and to localize barrier disruption to key organs.******Within insects a range of neuropeptides regulate transcellular and paracellular transport across epithelia. In my third objective, I will screen neuropeptides for effects on chill tolerance, and determine whether induced variation in chill tolerance is associated with an altered ability of flies to maintain ion homeostasis in the cold. Further, I will determine which neuropeptides and receptors are most likely to be relevant to chill tolerance adaptation and plasticity, using tissue-specific RNA-seq.**

我的长期目标是对温度如何限制动物的表现有一个综合的理解，我将开始关注耐寒性。大多数昆虫都是对寒冷敏感的，这意味着它们在相对温和的低温下会受到非冷冻伤害。对这些昆虫来说，冷暴露的主要后果是破坏离子和水的稳态;冷诱导的细胞外[K+]的升高使细胞去极化，导致损伤和死亡。然而，通过热适应或可塑性，昆虫可以在寒冷中更好地维持离子稳态，从而避免伤害。因此，离子调节器官的生理变化可能是昆虫耐寒性变化的基础。** 昆虫离子平衡是通过马氏管（MT）和肠道的协调运输特性来维持的。这些器官与耐寒性高度相关，但低温损害其功能的机制尚不清楚。在我的第一个资助周期中，我建议使用果蝇，蝗虫和蟋蟀来研究：1）寒冷对离子调节器官的运输生理学的影响，2）寒冷对细胞旁上皮屏障的影响，以及3）耐寒性的内分泌控制。在我的第一个目标中，飞蝗将被用来研究温度如何直接影响MT和肠道上皮细胞中的跨细胞离子转运。为了实现这一点，我将使用各种技术来研究温度对离子和水的运输的影响，并量化单个运输的相对贡献，以维持离子平衡在寒冷。然后，这些技术将适用于耐寒性不同的蟋蟀物种，以检查上皮细胞的热适应。分子不仅可以通过跨细胞途径，而且可以通过细胞旁途径穿过上皮，其紧密性由分隔连接（SJ）介导。在我的第二个目标，我将确定的作用，SJS和它们的组成蛋白质在果蝇耐寒性。我将开始通过研究如何热适应调节肠道屏障特性和SJ蛋白在果蝇的组织特异性表达模式。同时，我将使用蝗虫来确定冷诱导的SJ破坏是否是昆虫面临的常见挑战，并将屏障破坏定位到关键器官。在昆虫体内，一系列神经肽调节跨上皮细胞的跨细胞和细胞旁转运。在我的第三个目标中，我将筛选神经肽对耐寒性的影响，并确定耐寒性的诱导变化是否与果蝇在寒冷中维持离子稳态的能力改变有关。此外，我将确定哪些神经肽和受体最有可能与耐寒适应和可塑性相关，使用组织特异性RNA-seq。