Glossary

While ‘Drosophila’ is champion, these model organisms are players, too.

The axolotl (Ambystoma mexicanum) is a large salamander that keeps its gills and tail fin for its entire life and maintains an aquatic lifestyle. It is considered a food source in Mexico. Famous for its regenerative abilities—of limbs, spinal cord and lens—it is an important model organism for researching vision, neural transmission, renal function, embryogenesis, heart development and olfaction. The IU Axolotl Colony was founded in 1957 by Rufus R. Humphrey, who researched the creature’s mutant genes. The colony has been supported by the NSF since 1969 as a genetic resource center to provide material to scientists all across the U.S. George Malacinski, a professor of biology whose research centers around developmental genetics and molecular embryology of various amphibian systems, is director of the colony.

C. elegans:

Despite its lovely name, C. elegans is a nematode—a small worm. It grows to about 1 mm in length, lives in the soil and is especially fond of rotting vegetation. C. elegans is important as a model organism because it is about as primitive an organism that exists while still sharing many characteristics of human biology. Its popularity also stems from the fact that it is transparent, allowing cells to be studied using a microscope. The creature lives only for three days, and its genome has been completely sequenced, giving scientists a full dictionary of genes to choose from for research. At IU, several scientists are involved in researching the little worm, including Susan Strome, a professor of biology researching embryo pattern formation and germ cell development, and Wayne Forrester, assistant professor of biology, researching cell migration. Joining the IU faculty from U.C. Davis this coming fall is Jonathan M. Scholey, who works on fundamental problems in cell biology with C. elegans as a conduit.

Daphnia:

Michael Lynch, professor of biology at IUB, works with nematodes and zebrafish, but most notably he employs the water flea (Daphnia) for genomic study. Daphnia produce most of their young without mating through parthenogenetic reproduction—unfertilized eggs mature into larvae. Females produce young every two or three days and it is possible for one female to have 13 billion descendants. According to Lynch, Daphnia is not a flea at all, but is a micro-crustacean that lives in lakes and ponds. “There are many reasons for extending genomics to Daphnia, but one of the prime ones is that more is known about the ecology of this critter than any other animal,” he said. “There is a real need for a model organism with well understood ecology and genetics if we are to understand how genomes evolve in the natural world.” Lynch is involved with the Daphnia Genomics Consortium which has as its goal the “eventual, full characterization of the genome of D. Pulex, and the development of an array of molecular, cell and development tools comparable to those currently available for other model organisms, like flies and worms.”

Helianthus:

Loren H. Rieseberg, the Class of ‘54 Professor of biology at IUB, works with Helianthus, the sunflower, a genus that includes several cultivated plants and a number of wild species. His work is important mainly for agricultural reasons since sunflower represents a major oil seed crop. “There is really quite a long history of research on sunflowers on this campus dating back to the 1940s,” said Rieseberg. Charles Heiser, Distinguished Professor emeritus of botany, came to IU from the University of California at Berkeley in 1947, the same year his first research article was published. Heiser’s interest in sunflowers involved the natural hybridization, the evolutionary significance and, later, in the origin of domesticated plants. Today, Rieseberg’s research involves speciation genetics, genetics of domestication, conservation genetics and reproductive system evolution.

“Eastern North America is considered to be one of five regions in the world in which food production arose altogether independently,” Rieseberg said. “Until recently, the strongest support for this hypothesis has come from the sunflower, which archaeological data suggest was domesticated in the eastern U.S. However, this view has been challenged by the discovery of very large domesticated sunflower achenes from archaeological sites in Southern Mexico.” Rieseberg is assessing the geographical origins of the domesticated sunflower and the genetic basis of domestication traits.

Xenopus laevis:

A very large frog, Xenopus laevis is a commonly used model system for studying vertebrate embryonic development. With a life span of about five months, scientists are able to conduct multigeneration genetic analysis with this creature, and much of our current understanding of early embryonic development derives from experiments performed in the Xenopus laevis embryo. Anton Neff and Anthony Mescher, an associate professor and professor, respectively, in the Department of Medical Sciences in Bloomington, are working on the frog’s regenerative abilities, however. They are part of a team seeking the frog’s genes that are responsible for spinal cord regeneration and the regeneration of limb tissues such as skin, nerves, bones and muscles. It is hoped that once the genes are found, then information from the human genome project can be used to identify corresponding genes in humans.