Physiological and Molecular Mechanisms of Stress Tolerance in a Polar Insect

极地陆地环境通常被描述为沙漠，在那里，水的可用性被认为是陆地生物分布的最重要限制之一。此外，冬季持续的低温威胁着生存，而夏季的温度则挑战着生物从冰冻到干燥的广泛变化和快速转变。全球变暖进一步影响了南极陆生植物和节肢动物群落所经历的极端热水条件，特别是由于南极半岛的冰川退缩。本研究将重点关注生活在这一充满挑战和变化的环境中的最大、最南端的全变性昆虫——陆生蠓（Belgica antarctica）的热适应和水适应。在冰冻的基质中过冬的蠓幼虫必须忍受类似沙漠的环境300多天，因为从生物学上来说，自由的水以冰的形式是不可用的。在夏季，除了咸水飞溅之外，幼虫可能会浸入融化的水或从企鹅群和海豹滩流出的水中。另一种情况是，当幼虫的微栖息地变干时，它们可能会遭受长时间的干燥。由于它们的体积小，相对不动和适合的微栖息地的斑块性，因此幼虫可能遭受包括干燥，低或高渗透条件，高盐度暴露和长时间缺氧在内的压力。研究工作将集中在与这些蠓的耐应力机制有关的三个方面：(1)获得南极蠓所经历的小气候条件的详细特征，特别是与季节性和南极洲帕尔默站附近微生境类型之间的热多样性和水分多样性有关的小气候条件；(2)研究水分供应的极端波动及其对生理和分子反应的影响，以确定蠓幼虫是否利用低温保护性脱水机制进行冬季生存，以及编码热休克蛋白和其他基因的基因是否在幼虫对脱水和补液的反应中上调；(3)研究低温保护剂从植物到寄主的饮食传播，这将验证蠓幼虫通过从寄主植物获取低温保护剂来增强对干燥和温度胁迫的抗性的假设。该项目将为中小学教育工作者及其学生提供外联服务。该团队将包括一名教师，他将从全面参与研究中获得专业利益，并将协助向其他教师及其学生提供外联服务。在帕尔默站，考察队将通过电子邮件和数码图片与老师和小学生交流每天的研究进展，以激发他们对南极生物和科学研究的兴趣。这些努力将辅以在当地学校和全国教师会议上的演讲，以及在教育期刊上发表与低温生物学和极地生物学有关的实践性、研究性文章。此外，主要研究人员将继续致力于培养研究生和博士后学者，以及本科生，提供更多的研究经验，包括发表科学论文和在国家会议上发言。

Polar terrestrial environments are often described as deserts, where water availability is recognized as one of the most important limits on the distribution of terrestrial organisms. In addition, prolonged low winter temperatures threaten survival, and summer temperatures challenge organisms with extensive diel variations and rapid transitions from freezing to desiccating conditions. Global warming has further impacted the extreme thermal and hydric conditions experienced by Antarctic terrestrial plant and arthropod communities, especially as a result of glacial retreat along the Antarctic Peninsula. This research will focus on thermal and hydric adaptations in the terrestrial midge, Belgica antarctica, the largest and most southerly holometabolous insect living in this challenging and changing environment. Overwintering midge larvae encased in the frozen substrate must endure desert-like conditions for more than 300 days since free water is biologically unavailable as ice. During the summer, larvae may be immersed in melt water or outwash from penguin colonies and seal wallows, in addition to saltwater splash. Alternatively, the larvae may be subjected to extended periods of desiccation as their microhabitats dry out. Due to their small size, relative immobility and the patchiness of suitable microhabitats, larvae may thus be subjected to stresses that include desiccation, hypo- or hyperosmotic conditions, high salinity exposure, and anoxia for extended periods. Research efforts will focus in three areas relevant to the stress tolerance mechanisms operating in these midges:(1) obtaining a detailed characterization of microclimatic conditions experienced by B. antarctica, especially those related to thermal and hydric diversity, both seasonally and among microhabitat types in the vicinity of Palmer Station, Antarctica; (2) examining the effects of extreme fluctuations in water availability and effects on physiological and molecular responses - to determine if midge larvae utilize the mechanism of cryoprotective dehydration for winter survival, and if genes encoding heat shock proteins and other genes are upregulated in larval responses to dehydration and rehydration; (3) investigating the dietary transmission of cryoprotectants from plant to insect host, which will test the hypothesis that midge larvae acquire increased resistance to desiccation and temperature stress by acquiring cryoprotectants from their host plants. This project will provide outreach to both elementary and secondary educators and their students. The team will include a teacher who will benefit professionally by full participation in the research, and will also assist in providing outreach to other teachers and their students. From Palmer Station, the field team will communicate daily research progress by e-mail supplemented with digital pictures with teachers and their elementary students to stimulate interest in an Antarctic biology and scientific research. These efforts will be supplemented with presentations at local schools and national teacher meetings, and by publishing hands-on, inquiry-based articles related to cryobiology and polar biology in education journals. Furthermore, the principal investigators will maintain major commitments to training graduate students and postdoctoral scholars, as well as undergraduate students by providing extended research experience that includes publication of scientific papers and presentations at national meetings.