How an individual responds to environmental stress (temperature changes, toxins, disease, social interactions) affects how that individual acts, its ability to reproduce, and its lifespan. Therefore, it is important to understand how the genetic make-up of an individual determines how it responds to stress; and how populations evolve in response to their environmental conditions. This project addresses these questions using natural snake populations that consist of either slow-living (low reproduction, extended lifespan) or fast-living (high reproduction, shortened lifespan) individuals who respond to environmental stresses in different ways, but only slightly differ in genetic make-up. Stress experiments on these populations are used to characterize their physiological differences in stress response. New DNA sequencing technologies are then used to identify the underlying genes that allow them to respond to stress in different ways. Once these genes have been identified, they are explored further to understand how they have changed in the different populations that have been living under different environmental conditions.
This research will help us to understand what genes are important for stress response in natural populations, and how they evolve in response to different environmental stress conditions. Many of the genes investigated here are involved in metabolism, diabetes and aging. Because animals share many of the same genes with only slight differences, experiments using snakes populations that naturally differ in reproduction, lifespan and stress response can help us to understand the genes responsible for these traits in many animal species, including livestock and humans.
How an individual responds to environmental stress (e.g., temperature, toxins, disease) at the cellular level affects how that individual behaves, its ability to reproduce, and its lifespan. To understand how stress will affect the life of an individual, it is important to understand if genetically different individuals respond to stress differently. Furthermore, it is important to understand how populations change over time (evolve) in response to their environmental conditions. Experiments in laboratory model organisms (e.g., mouse, fruit fly, and nematode) have identified a large number of genes that affect aging, reproduction, and stress response. These laboratory animals live in controlled environments and are typically genetically identical, thus it is difficult to predict if and how the results from these lab experiments can translate to natural populations of animals (including humans) that are genetically diverse and live in varying environments; thus, testing the ability of these results to translate is now the goal. This project works towards that goal by using natural snake populations that contain either slow-living (low reproduction, extended lifespan) or fast-living (high reproduction, shortened lifespan) individuals to address these questions: how do animals respond to stress at the molecular level; how does stress response vary across populations; and how is stress response integrated with the processes of aging and reproduction. Research Findings We determined how slow-living and fast-living populations of snakes respond the same and how they respond differently to a stressful temperature. In response to stress, both types of snakes increased their levels of stress hormone (corticosterone) in their blood. Additionally, both types of snakes activated many genes in response to the stress, including some related to metabolism. The fast- and slow-living snakes differ in their levels of reactive oxygen species (potentially damaging molecules) in their blood, and in their ability to protect and repair their DNA from mutations induced by stress. These differences suggest that the slow-living snakes are better able to protect themselves at the molecular level from negative affects of physiological stress. To understand how these two types of snakes differ at the genetic level, we developed and implemented a sequence-capture method that targeted 500 genes (based-on results from experiments on lab model animals and our previous results). We then compare the DNA sequence for the 500 genes across 126 individuals from the fast- and slow-living snake populations. We found that the individual snakes had different genetic sequences (alleles) in many of these genes that are involved in stress response, metabolism, growth, and aging. The existence of this natural genetic variation in these genes indicates that it is possible for natural selection to cause these traits to evolve in these natural populations; and we continue our analyses to test for this. Collectively, the results from this research indicates that findings from laboratory model organisms provide good predictions as to which cellular processes and genes are involved in stress response, lifespan and reproduction in natural populations. But, how these cellular processes and genes respond to stress in natural populations is not always as predicted. These results are currently be prepared for publication in peer-reviewed scientific journals. Broader impacts through teaching, training and outreach This project provided research training in the generation and analysis of genetic data for three post-doctoral researchers, two PhD students, and an undergraduate student. Additionally this project provided an opportunity to integrate research-based projects into 7-8th grade classrooms in collaboration with the NSF GK-12 program, including lessons on: conducting field research (www.youtube.com/watch?v=jZYmogMcItw); DNA technology (www.youtube.com/watch?v=P0DCj6qyj4c); metabolism; and genetic inheritance. Not only did this provide middle school children with the opportunity to conduct actual research projects, it also provided a PhD student with the opportunity to learn how to relate science to a general audience. Intellectual merit This project developed methodological protocols for targeting a large number of DNA sequences from natural populations of "non-model" animals, and protocols for analyzing this large amount of sequencing data. These protocols and data will be freely available to the public via websites. This research will help us to understand what genes and cellular processes are important for stress response in natural populations, and how these populations have evolved in response to different environmental stress conditions. In this way, this research (1) furthers our understanding of how diverging environmental stresses may drive evolution at the molecular level to potentially affect traits such as lifespan and reproduction, and (2) improves our ability to predict how findings in laboratory model organisms may translate to natural populations. Many of the genes investigated in this project are involved in metabolism, diabetes, and aging. Because animals have nearly all the same genes, with only slight differences, experiments using snake populations that naturally differ in reproduction, lifespan and stress response can help us to understand the genes responsible for these traits in other animal species, including livestock and humans.
