Derrick K.
Mathias
dmathias@darkwing.uoregon.edu
University
of Oregon
Center for Ecology & Evolutionary Biology
University of Oregon
Eugene, OR 97403 USA
Advisors:
Bill Bradshaw,
Program in Ecology & Evolution
Chris
Q. Doe, Institute of Neuroscience
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Research Interests
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The major emphasis of my research is on the evolutionary genetics of photoperiodic time measurement, the basis for seasonal control of biological processes common among organisms in the temperate zone. Photoperiod (i.e. day length) varies predictably over the course of a year, providing a reliable cue for the timing of seasonal events, such as the control of development in terrestrial arthropods and flowering in angiosperms. The specific aim of my research is to resolve the genetic basis of seasonal control of holometabalous development in insects and how genetic variation of such regulation arises and is maintained among populations. To address these questions I am using the pitcher-plant mosquito, Wyeomyia smithii. In this species holometabolous development proceeds through four larval instar stages and a pupal stage from which adults emerge. This cycle can be interrupted at the third or fourth larval stage, a point at which developmental arrest is initiated. Known as diapause the onset and termination of this state is cued by changes in photoperiod and most likely involves control of the edysteroidogenic pathway. What is unknown is how changes in photoperiod is measured and how that information is transmitted to stop or start the molting process.
Model Organism
Wyeomyia smithii is an ideal research organism for investigating photoperiodic control of development. Its geographic range spans from the Gulf of Mexico to northern central Canada, providing a broad photic environment to which populations of this species have evolved. For example, critical photoperiod, which is the average day length necessary to initiate or terminate diapause, differs by more than 10 standard deviations of the mean between populations in Florida and Maine. Furthermore, with the recent publication of the genome of the mosquito Anopheles gambiae, this species has become amenable to both genomic and quantitative genetic approaches.
Experimental Approach
Currently I am taking a candidate gene approach by investigating the role in photoperiodic response of genes involved in the circadian clock. From research of circadian clocks in Drosophila, we know that there are at least eight genes involved in generating and maintaining circadian rhythms and numerous other genes under clock control. To date in W. smithii I have isolated one of the core clock genes timeless, as well as one of its regulators shaggy. This portion of the circadian pathway is particularly interesting because the protein product of timeless is known to interact with a blue light receptor encoded by the gene cryptochrome. I am now in the process of assessing the degree of polymorphism of these two genes between populations of W. smithii with divergent photoperiodic phenotypes, as well as the degree of variation in their expression patterns using real-time quantitative pcr. If these initial studies prove promising, I will investigate associations between photoperiodic phenotype and polymorphism or expression pattern on a finer scale using recombinant hybrids of crosses between populations. Additionally, I plan to isolate other candidate genes in the circadian pathway with the intention of taking the same experimental approach. Wyeomyia smithii is an ideal research organism for investigating photoperiodic control of development. Its geographic range spans from the Gulf of Mexico to northern central Canada, providing a broad photic environment to which populations of this species have evolved. For example, critical photoperiod, which is the average day length necessary to initiate or terminate diapause, differs by more than 10 standard deviations of the mean between populations in Florida and Maine. Furthermore, with the recent publication of the genome of the mosquito Anopheles gambiae, this species has become amenable to both genomic and quantitative genetic approaches.
Experimental Approach
Currently I am taking a candidate gene approach by investigating the role in photoperiodic response of genes involved in the circadian clock. From research of circadian clocks in Drosophila, we know that there are at least eight genes involved in generating and maintaining circadian rhythms and numerous other genes under clock control. To date in W. smithii I have isolated one of the core clock genes timeless, as well as one of its regulators shaggy. This portion of the circadian pathway is particularly interesting because the protein product of timeless is known to interact with a blue light receptor encoded by the gene cryptochrome. I am now in the process of assessing the degree of polymorphism of these two genes between populations of W. smithii with divergent photoperiodic phenotypes, as well as the degree of variation in their expression patterns using real-time quantitative pcr. If these initial studies prove promising, I will investigate associations between photoperiodic phenotype and polymorphism or expression pattern on a finer scale using recombinant hybrids of crosses between populations. Additionally, I plan to isolate other candidate genes in the circadian pathway with the intention of taking the same experimental approach.________________________
Publications
... none currently ...