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

Board Of Regents, Nshe, Obo University Of Nevada, Reno, Reno NV

Investigators

Abstract

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.