Evolution of germline sex determination
How did female nematodes evolve into hermaphrodites?
The oldest project in the lab seeks the genetic and molecular causes of self-fertility in Caenorhabditis nematodes. This work is focused on characterizing the evolutionary changes in the genetic circuits that regulate germ cell sex determination, changes that were essential for a new sexual mode to emerge. We pursue this in "the worm," C. elegans, which has a rich history and amazing experimental toolkit. We also study C. briggsae, which independently evolved the same trait. This allows us to pose questions about convergent evolution, and the reproducibility of evolutionary mechanisms.
The oldest project in the lab seeks the genetic and molecular causes of self-fertility in Caenorhabditis nematodes. This work is focused on characterizing the evolutionary changes in the genetic circuits that regulate germ cell sex determination, changes that were essential for a new sexual mode to emerge. We pursue this in "the worm," C. elegans, which has a rich history and amazing experimental toolkit. We also study C. briggsae, which independently evolved the same trait. This allows us to pose questions about convergent evolution, and the reproducibility of evolutionary mechanisms.
Consequences of self-fertility
How did selfing alter the genome and reproduction?
For C. briggsae, it appears selfing led to the loss of thousands of protein-coding genes, most functioning only or mostly in XO males. Among the lost genes are those encoding sperm factors, such as the MSS glycoproteins that are required for competitiveness but not baseline fertility. See Yin et al. (2018).
For C. briggsae, it appears selfing led to the loss of thousands of protein-coding genes, most functioning only or mostly in XO males. Among the lost genes are those encoding sperm factors, such as the MSS glycoproteins that are required for competitiveness but not baseline fertility. See Yin et al. (2018).
"The C. elegans of fish"
How can a vertebrate be a simultaneous AND a sequential hermaphrodite?
The mangrove killifish, Kryptolebias marmoratus, is an odd little fish. Like C. elegans, it evolved a self-fertile hermaphrodite from a standard male-female ancestor. It also shares the capacity to outcross through rare males. In contrast to the worms, however, males are produced via sex change (sequential hermaphroditism). Kmar work in the lab is currently addressing these questions:
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Non-model nematodes
What about nematodes that matter for health and agriculture?
Through the interests of trainees, the lab is branching out to consider nematodes that have a more direct human impact than our beloved Caenorhabditis system. These include:
- Fig-associated nematodes. Led by Dr. Justin Van Goor, we are exploring the interactions between nematodes and the figs, pollinating and non-pollinating fig wasps, fungi, and prokaryotes with which they interact. At left is a culture of Fusarium fungus collected from the inside of a Ficus petiolaris fig from Baja California Sur, Mexico.
- Filarial parasitic nematodes. Led by BISI-CBBG student Kevin Hackbarth, we are examining sex chromosome evolution in several parasitic species. This work is in collaboration with Dr. Julie Dunning-Hotopp of the University of Maryland School of Medicine.
Through the interests of trainees, the lab is branching out to consider nematodes that have a more direct human impact than our beloved Caenorhabditis system. These include:
- Fig-associated nematodes. Led by Dr. Justin Van Goor, we are exploring the interactions between nematodes and the figs, pollinating and non-pollinating fig wasps, fungi, and prokaryotes with which they interact. At left is a culture of Fusarium fungus collected from the inside of a Ficus petiolaris fig from Baja California Sur, Mexico.
- Filarial parasitic nematodes. Led by BISI-CBBG student Kevin Hackbarth, we are examining sex chromosome evolution in several parasitic species. This work is in collaboration with Dr. Julie Dunning-Hotopp of the University of Maryland School of Medicine.