video: The predatory form of P. pacificus devours another worm, C. elegans. view more
Credit: Dan Bumbarger
BLOOMINGTON, Ind. -- An Indiana University biologist has been awarded $750,000 to identify the genetic mechanism that makes up a "switch" allowing some genetically identical species to develop strikingly different physical characteristics based on their environment, a phenomenon known as "polyphenism."
The National Science Foundation will provide the funds to Erik Ragsdale, an assistant professor in the IU Bloomington College of Arts and Sciences' Department of Biology.
Like a train approaching two sets of tracks, the "switch" under investigation can cause species with polyphenism to "hop rails" from one developmental pathway to another in response to the environment. Some biologists suggest this ability may even enable "accelerated evolution."
"Despite the potential evolutionary consequences of developmental plasticity, such as polyphenism, we still don't know much about the genetic mechanisms of the switches controlling it," Ragsdale said. "This research project will be a genetic analysis of how polyphenism responds to input from the environment, and how its regulation changes over evolutionary time."
To conduct the investigation, Ragsdale will study nematode worms. In the same way the finches studied by Charles Darwin had beaks specifically suited to different types of seeds and insects, nematode worms possess a wide array of mouthparts, perfectly tailored to specific types of food.
"These worms lead virtually every lifestyle known to animals, based upon shapes of their mouths," Ragsdale said. "They can be vegetarians, meat-eaters, omnivores, bacteria-feeders and parasites. In nematodes with polyphenism, their feeding structures are a response to specific environments, not totally pre-determined by genes."
The worm species in the IU study, Pristionchus pacificus, can develop one of two types of mouth -- despite possessing the same genome -- based on their environment. If they develop in an environment rich in food and space to grow, P. pacificus will grow a narrow mouth for peaceably grazing upon bacteria. If they develop in an overcrowded or starved environment lacking in food, they will grow a wide mouth with large, moveable teeth -- suitable for feeding upon other worms.
As a postdoctoral researcher at Germany's Max Planck Institute for Developmental Biology in 2013, Ragsdale was part of the team that first discovered the gene that acts as the switch in these worms, triggering the "irreversible decision" that determines how they will feed for the rest of their lives.
The new research at IU under the NSF's support will build upon this past work by studying the precise function of other genes discovered to act in the switch, investigating how they interact with other genes, and reconstructing their evolution in related species, including those lacking developmental polyphenism.
In addition, the grant will provide educational opportunities to six high school students and six high school teachers over the next four years. Both groups will get the chance to contribute to the research through the Jim Holland Summer Science Research Program, an intensive, weeklong research training program for underrepresented high school students pursuing careers in STEM, and the IU Biology Summer Science Institute, which pairs high school science teachers with IU researchers to develop classroom modules based on research at the university.
The NSF funds will also provide support for a postdoctoral researcher, a graduate student and several IU undergraduate students to assist in the study.
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