EAGER: Physiological Canalization and Individual Variation

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In the morning people wake up and have breakfast, they eat lunch around noon, and in the evening they eat dinner. If it is too hot, or too cold, one turns on the air conditioner or the furnace. When people are sick or suffering from a laceration, they seek treatment with antibiotics (if appropriate) or rest in bed. However, in the natural environment for wild outbred populations of organisms, life has many more unexpected environmental variations. For the fish Fundulus heteroclitus (the focus of this proposed study), the environment is both unpredictable and extremely variable. In their natural habitat Fundulus live in a constantly changing environment because they feed in the upper estuaries of coastal North America. At low tides they are either in deeper tidal creeks experiencing lower ocean temperatures (10-25°C) or, especially in spring and summer, can become temporarily lodged in the upper estuaries in warm tidal pools (25-35°C). They experience daily variation in salinity as they move with the tide up into marshes, from full strength seawater (33 parts per thousand, ppt) to less than 3 ppt if it is raining heavily. This application focuses on how environmental variation affects phenotypic variation in mRNA expression. The hypothesis proposed in this application is that much variation is hidden by the variable ecological settings where most natural populations exist. The counter-intuitive hypothesis is that for a subset of genes, the physiological responses to variable environments constrain inter-individual variation in mRNA expression, and in so doing mask functional genetic variation or polymorphisms. If correct, then physiological canalization of gene expression hides genetic variation. Thus, this research provides a novel perspective on how so much hidden genetic variation arises and why it persists in natural populations. There are no prior analyses aimed at understanding how the environment affects the variance in mRNA expression, and a major impediment to such studies is that estimating variance requires specific experimental designs with large sample sizes. This application overcomes the design challenges, and will yield unique statistical analyses of how the variance in gene expression is a function of the environment, and in turn affects evolutionary processes. The fundamental importance of this proposed research is that it explores mechanisms whereby much genetic variation may be hidden, and addresses how large amounts of genetic variation can be maintained in natural species populations. The findings have the potential to significantly alter views of the results of experiments conducted under standard, well-controlled laboratory conditions, and thus influence physiological, evolutionary and human health research.This research has broader impacts in three areas. First, contributions to the scientific community include a large dataset on gene expression, cDNA sequences, and proximal promoters that can be used in other studies on metabolism, physiological acclimation and the regulation of gene expression. These data will be made available publically. Second, a graduate student will be trained in a diversity of biological fields, including genomics, ecology and physiology, and in statistical analyses. Finally, undergraduate students will be attracted to this project through interactions with programs at the University of Miami that recruit students from underrepresented groups and engage them in hands-on scientific research.