Response to climate warming in a tropical ectotherm: an investigation of epigenetic and mitochondrial haplogroup effects

现代生物学的一个中心前提是，遗传和个体变异最终由基因组中的DNA碱基序列控制。然而，分子遗传学的发现揭示了一个更复杂的现实，在这个现实中，一系列可遗传的化学信号决定了基因在何时、何地、在什么环境背景下被开启或关闭。这种对基因表达的控制比DNA序列对环境影响更敏感，环境诱导的变化可以代代相传，从而影响后代的生长、代谢、神经发育和生育能力的变化。一个尚未解决的主要问题是，获得性信息的跨代传播是否使生物体能够应对环境挑战。该项目利用节肢动物模型物种的独特生殖特征，即胚胎在外部透明的孵化囊中发育，并可以被监测和操纵，以确定环境诱导的表观遗传效应是否在改变的基因表达模式从父母传给后代中起因果作用。该项目将为K-12教师、高中生、本科生、研究生和博士后学者提供培训，并将包括高中推广活动，形式包括博物馆展品、实习、演示、分子技术培训、科学项目竞赛咨询和课程开发援助。自然发生的线粒体变异对小非编码RNA(SncRNAs)对核基因表达的表观遗传调控的影响及其对环境挑战的进化反应的影响尚不清楚。该项目将利用在伪蝎种群中共存的两个高度分化的线粒体单倍群(A，B2)来确定作用于这一遗传多样性池的选择是否能够使这种热带节肢动物通过适应和/或环境诱导的表观遗传变化来响应温度诱导的生理胁迫。该项目将包括：(1)检测A和B2单倍群对逐渐升高的温度的反应的多世代实验；(2)表观遗传反应实验，其中单倍群的复制将在对照和高温下作为分裂仔猪饲养，并检测来自对照和高温处理杂交的后代；以及(3)将差异表达的SncRNAs显微注射到早期胚胎中，以评估可能的因果表观遗传对高温反应的影响。综上所述，这些实验将解决对环境挑战的适应性进化反应的可能性，并将确定：(1)不同的线粒体单倍群的反应不同；(2)表观遗传效应是适应性的还是病理性的；(3)表观遗传效应是通过父系或母系传递的；以及(4)差异表达的SncRNA在环境诱导的表观遗传修饰的传递中起因果作用。

A central premise of modern biology has been that inheritance and individual variation are ultimately controlled by the sequence of DNA bases in the genome. However, discoveries in molecular genetics are revealing a more complex reality in which an array of heritable chemical signals determine when, where and in what environmental contexts genes are turned on or turned off. Such control of gene expression is much more sensitive to environmental influences than DNA sequence, and environmentally-induced changes can be transmitted across generations to effect changes in offspring growth, metabolism, neurological development and fertility. A major unresolved question is whether transmission of acquired information across generations enables organisms to respond to environmental challenges or not. This project exploits the unique reproductive characteristics of a model arthropod species, in which embryos develop in an external, transparent brood sac and can be monitored and manipulated, to determine whether environmentally-induced epigenetic effects play a causal role in the transmission of altered gene expression patterns from parents to offspring. The project will provide training for K-12 instructors, high school students, undergraduates, graduate students and a postdoctoral scholar and will include high school outreach in the form of museum exhibits, internships, presentations, training in molecular techniques, advising in science project competitions and assistance with curriculum development. The impact of naturally occurring mitochondrial variation on the epigenetic regulation of nuclear gene expression by small noncoding RNAs (sncRNAs) and its effects on evolutionary responses to environmental challenges are poorly understood. This project will exploit two highly divergent mitochondrial haplogroups (A, B2) that co-occur in populations of the pseudoscorpion, Cordylochernes scorpioides, to determine whether selection acting on this pool of genetic diversity can enable this tropical arthropod to respond to temperature-induced physiological stress through adaptation and/or environmentally-induced epigenetic changes. The project will include: (1) a multi-generation experiment to examine the response of A and B2 haplogroups to incrementally increasing temperatures; (2) an epigenetic response experiment in which replicates of the haplogroups will be reared as split broods at control and elevated temperatures, and offspring assayed from the control and elevated temperature treatment crosses, and (3) a study in which differentially-expressed sncRNAs will be microinjected into early-stage embryos to assess possible causal epigenetic effects on elevated temperature response. Taken together, these experiments will address the potential for an adaptive evolutionary response to environmental challenges, and will determine whether: (1) divergent mitochondrial haplogroups differ in their responses; (2) epigenetic effects are adaptive or pathological; (3) epigenetic effects are transmitted paternally or maternally, and (4) differentially expressed sncRNAs play a causal role in the transmission of environmentally-induced epigenetic modifications.