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，那里的水可获得性被认为是对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，而夏季的温度对生物体构成了挑战，因为它们具有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生植物和节肢动物群落所经历的极端高温和潮湿条件，特别是南极半岛冰川消退的结果。这项研究将集中在南极洲Belgica陆地吸虫的热适应和氢气适应方面，Belgica南极洲是生活在这个充满挑战和变化的环境中最大和最南端的全变形昆虫。被包裹在冰冻底物中越冬的幼虫必须忍受沙漠般的条件300多天，因为从生物上讲，游离水不能以冰的形式存在。在夏季，除了海水飞溅，幼虫还可能浸泡在融化的水中，或者从企鹅和海豹群中喷出。或者，当幼虫的微生境干涸时，幼虫可能会经历较长的干燥期。由于幼虫体型小，相对固定，适宜的微生境参差不齐，因此可能会受到包括干燥、低渗或高渗条件、高盐度暴露和长期缺氧等压力。研究工作将集中在三个与在这些蚊子中运行的胁迫耐受机制有关的领域：(1)获得南极蚊虫所经历的小气候条件的详细特征，特别是与温度和氢气多样性有关的小气候条件，包括季节和南极帕尔默站附近的小生境类型；(2)研究可用水的极端波动的影响以及对生理和分子反应的影响--以确定蚊虫幼虫是否利用低温保护脱水机制来越冬生存，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复水的反应中上调；(3)研究低温保护剂从植物到昆虫寄主的饲料传递，这将验证吸虫幼虫通过从寄主植物获取低温保护剂而获得对干燥和温度胁迫的抗性的假说。该项目将向中小学教育工作者及其学生提供外展服务。该小组将包括一名教师，他将通过全面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。在帕尔默站，野外团队将通过电子邮件和数字图片与老师和他们的小学生交流日常研究进展，以激发人们对南极生物学和科学研究的兴趣。除了这些努力，还将在当地学校和全国教师会议上发表演讲，并在教育期刊上发表与低温生物学和极地生物学有关的动手的、基于探究的文章。此外，首席调查员将继续致力于培训研究生和博士后学者以及本科生，提供广泛的研究经验，包括发表科学论文和在全国会议上发言。

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.