For BRIN, SPUR, or REU students looking for research for the summer of 2016, I have a few projects in mind. Scroll down, I have highlighted them below. We should get together and talk about what interests you. I am also open to ideas for projects that you may wish to pursue. So, contact me with your ideas (firstname.lastname@example.org)!
I am interested in egg size and how shifting egg size can influence the earliest developmental events in the embryo. In exploring this idea I generated two different large-egg producing populations of fruit flies (Drosophila melanogaster) by using artificial selection for egg size (a direct selection method) and by raising them in colder temperatures (an indirect selection method). The cold-raised lines certainly do produce bigger eggs than their controls, but they also show some interesting behaviors, and life history trade-offs that we have only just begun to explore.
In 2016 I would very much like to try and take a close look at these cold-adapted flies. We need to compare the ovaries of these large-egg producing "cold moms" with the ovaries of their controls, as well as with those of the directly selected inbred lines. How does the architecture differ? Do indirectly-selected moms build their large eggs differently than the directly-selected moms?
In 2013 Nodia Lippert (Augie Class of 2014) and I counted the ovarioles (the subunits that make up ovaries) in two inbred D. melanogaster lines, derived from our artificially selected populations. We found that females from the large-egg line had ovaries with significantly fewer ovarioles. During the summer of 2014 Anna Cooper (Augie '15), Clayton Busch (Augie '15), and Samantha Johnson (U of Florida '17) used this same pair of lines to ask if we could detect the difference in adult ovariole number by examining the number of terminal filament (TF) stacks present at the larval-pupal (LP) transition. These are the cells that give rise to individual ovarioles in the adult. This work involved dissecting and triple-staining these small structures and using confocal microscopy to count the resulting stained cells. We found no reduction in the number of TF stacks in the LP stage from the large-egg line. This is not the predicted result based on the current understanding of how ovaries develop. In 2015 Augie students Deeksha Mohan ('17), and Caden Quintanilla ('18) expanded our sample size to seven more lines to ask how general this surprising pattern might be. They found variation in the number of TF among the large-egg lines. One line in particular seems to be departing from the "textbook" explanation of ovarian development. Cool! In 2016 we'd like to explore this further by examining the pupal stage in a few of these lines to see if we can detect apoptosis in the TF cells during ovary development. How, and at what point in development, are the number of TF stacks being reduced in order to accommodate the production of these large eggs in this line?
Another opportunity for the summer of 2016 also involves these inbred artificially selected lines. Recently, together with our collaborator Aashish Jha, we identified a number of candidate genes influencing egg size (see our paper in MBE, Jha et al. 2015), and some of these have also been associated with variation in ovariole number. Hippo, Wnt, and the Ecdysone pathways are of particular interest. We could design experiments to examine the differences in various elements of these pathways among our inbred lines using molecular techniques. If this interests you please email me!
Two Augustana students working on the cold-adapted lines in 2012 (Thanks Nodia and Brooke!) found that both males and females had larger body size relative to controls. Interestingly, when they were placed in the control temperature they retained this increase in body size completely. On average they were unable to reduce their investment in building larger bodies even when returned to the control environment (a loss of phenotypic plasticity). This type of genetic response often involves trade-offs with other life-history traits such as fecundity, longevity, and development time.
In observing these cold-adapted flies it is hard not to notice how much slower they move in response to most stimuli. I have been curious how much of this sluggish behavior is due to the temperature alone (strictly environmental) and how much has a genetic basis. In collaboration with Dr. Craig Spencer here at Augie, Ryta Wodzinski (Augie '14) worked on this project in 2013 (Hi Ryta!). She used small chambers that are specifically designed to measure the activity of flies (DAM2 Drosophila Activity Monitors) and found some fascinating differences between the two populations, especially in the circadian rhythms. We are interested in extending this analysis, and in examining these lines for sleep patterns, as well. This year I have been working to generate inbred lines from these cold-adapted populations. Many of the genes involved in sleep regulation in flies are known, and the availability of inbred lines means we could use genetic techniques to try and identify differences between the cold-adapted flies and their controls. If you are interested in following up on this please email me so we can discuss it.
One more way we have explored the laboratory evolution of these cold-adapted flies is another behavioral question. Female flies choose their mates after an elaborate courtship display. Augie student Brianna Grandprey ('17) used high-speed video equipment to analyze the courtship display of both the control and cold-adapted flies to ask if the females prefer mates from their own population (for example, larger females choosing larger males), or prefer males from the other population (that is, smaller females choosing larger males) and found significant differences in the behavior of the cold males resulting in much less mating success. Mate choice is a key element in reproductive isolation and has important evolutionary implications.
There are advantages to working with flies, but I am not limited to this model. I have worked with various other groups, so if you have ideas that involve another species lets talk about them. I am especially interested in groups we can collect locally.