Matthew Breuer
Our summer research was executed with the intent of further characterizing and understanding the process of programmed cell death (PCD) in the single-celled algae Chlamydomonas reinhardtii. To date, Chlamydomonas has been used for some studies of PCD, but the process has not been characterized to a high degree. A greater insight into this process is important for evolutionary studies and also may have applications in the waste management and biofuel production industries. Though my research partner Ally and I had made some progress on the project in prior semesters, we were able to make significant headway with the project during the summer months. Our research focused on two main goals. The first goal was to better understand the molecular underpinnings of the PCD process in Chlamydomonas. The second goal was to gain a better understanding as to why a unicellular organism might possess a genetic program which triggers its own death.
We tested for several physiological features that are common of cells undergoing PCD. Phosphatidylserine (PS) is a molecule that, under normal conditions, is evenly distributed across both sides of the plasma membrane. These molecules commonly are externalized, or "flipped", to the outer portion of the membrane during PCD. To determine if PS is flipped during PCD in Chlamydomonas, we exposed PCD-induced cells a fluorescent molecule which binds to PS molecules that have flipped. Our results indicate that only cells that had undergone PCD had externalized PS. We also used a fluorescent dye to test for the presence of reactive oxygen species (ROS) following PCD. Our results show that there is a distinct "burst" of these volatile molecules in Chlamydomonas cells that are undergoing PCD. Interestingly enough, however, this form of PCD appears to be a slow process, and we discovered that not all of the cells in a culture accumulate these reactive oxygen species at once. This indicates that the cells are not dying all at once, but at various times, following the stress.
In order to understand why a unicellular organism might undergo programmed cell death, we took media from cells which had undergone PCD and used it to grow new cells. We also measured the relative amount of death that occurred in cultures containing one species of Chlamydomonas and cultures containing two species of Chlamydomonas in order to determine if this organism preferentially dies in response to stress when surrounded by kin. Both of these experiments are currently ongoing.
As someone considering research as a career choice, this summer research was an excellent way to experience what a full-time research position might look like. Our work this summer also gave us ideas for other projects and experiments based on the results that we observed. I am especially thankful to Dr. Gaillard for the opportunity to be involved in such an in-depth project, particularly as an undergraduate. I believe that this type of hand-on research is the most effective way of improving the scientific skills of developing researchers. I would also like to thank the EURECA program for presenting us with the FAST grant. Because of this award, we were able to make significant progress towards our goals and hope to have the majority of this research finished by the end of the year.