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，水的供应被认为是陆地生物分布的最重要限制之一。此外，漫长的冬季低温威胁到生存，夏季温度挑战生物体广泛的昼夜变化和从冻结到干燥条件的快速转变。全球变暖进一步影响了南极陆地植物和节肢动物群落所经历的极端热和水分条件，特别是由于沿着南极半岛的冰川退缩。这项研究将集中在陆地蠓，Belgica anapartica，生活在这个充满挑战和不断变化的环境中的最大和最南端的holometabolous昆虫的热和水分适应。在冰冻的基质中越冬的蠓幼虫必须忍受300多天的沙漠般的条件，因为自由水是生物不可用的冰。在夏季，幼虫可能会浸泡在融化的水或从企鹅殖民地和海豹打滚，除了盐水飞溅。或者，幼虫可能会受到长时间的干燥，因为它们的微生境干燥。由于它们的体积小，相对固定和适合的微生境的斑块，幼虫可能因此受到压力，包括干燥，低或高渗条件，高盐度暴露，缺氧的延长时间。研究工作将集中在三个领域相关的压力耐受机制在这些蠓：（1）获得一个详细的小气候条件下所经历的B的特性。南极洲帕默站附近季节性和微生境类型中的水热多样性;（2）检查水可用性的极端波动的影响以及对生理和分子反应的影响-以确定吸浆虫幼虫是否利用低温保护脱水机制来越冬存活，以及编码热休克蛋白的基因和其他基因是否在幼虫对脱水和再水化的反应中上调;（3）研究抗冻剂从植物到昆虫宿主的食物传递，这将检验一个假设，即吸浆虫幼虫通过从寄主植物中获取防冻剂来增强对干燥和温度胁迫的抵抗力。该项目将向中小学教育工作者及其学生提供外联服务。该小组将包括一名教师，他将通过充分参与研究而在专业上受益，并将协助向其他教师及其学生提供外展服务。从帕尔默站，实地考察队将通过电子邮件与教师和小学生交流每日研究进展，并辅以数码图片，以激发他们对南极生物学和科学研究的兴趣。这些努力将通过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、基于调查的文章来补充。此外，主要研究人员将继续致力于培训研究生和博士后学者，以及本科生，提供扩展的研究经验，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.