The Research Samples series recounts the experiences of members of the research student community. Carla Bautista Rodriguez was curious by nature, and knew she wanted to pursue a career in science. It was the field of evolution that attracted her. "It explains almost every phenomenon we see," she says. She came from Madrid to do her master’s degree, followed by a fast-track PhD, in Christian Landry’s laboratory. "I liked the way he took a molecular approach to studying evolution," she says.
"We wanted to see if the hybrids adapted better to the stressful conditions of their environment than the parents," she explains. This knowledge can be used in agriculture, for example, to obtain better resistance to drought.
The advantage of yeasts, similar to those used in bread or beer fermentation, is their rapid life cycle. Carla can study the effects over a hundred generations of hybrids in her laboratory.
She tested the performance of yeast against UV radiation. Her initial hypothesis was that crossing species would give hybrids better resistance than their parents, but to her great surprise, this was not the case.
"It was the first time I realized what was involved in being a scientist. It’s not experiments that don’t work, it’s hypotheses that aren’t the way we thought they would be."
-- Carla Bautista Rodriguez, PhD graduate "I went to see Christian Landry to tell him that it wasn’t working, that we had to change our minds. He told me that we couldn’t just change, we had to find out why we were observing this phenomenon. He encouraged me to continue. That was the first time I realized what it meant to be a scientist. It’s not experiments that don’t work, it’s hypotheses that aren’t as we thought."
And so began Carla’s "journey of refutation". She put forward a second hypothesis, which the results further refuted. Finally, a theoretical model developed 100 years ago, the Haldane sieve, was used to explain these observations.
Normally, a mutation appears in one copy of the chromosome. To have a beneficial effect, it sometimes needs to be transferred to the other copy. By analyzing the yeast genome over the generations, Carla noticed that hybrid yeasts often contained only one copy of the beneficial mutation, unlike their parents, who had two.
"Hybrids have difficulty making the transition from one copy to two copies. As they only have one copy of the mutation, it does not fully express its beneficial effects, preventing it from passing through the Haldane sieve and becoming fixed in the population, unlike the parents. This explains their poor ability to adapt under these conditions", she adds.
In addition to agriculture, Carla’s discovery also has health implications. "This phenomenon has been identified as responsible, in the majority of cases, for antifungal resistance as well as cancer cell evolution."
Her results were published in the prestigious journal Nature Communications and posted on the Nature blog . She believes her particular path sparked the journal’s interest. "We told the story without hiding anything. Sometimes we disprove hypotheses, we come up against barriers. To explain how we got here, we had to explain everything first."
An exceptional career
Carla’s international studies were made possible by one of Spain’s most prestigious scholarships, the La Caixa Foundation Scholarship, which allowed her to choose any university. "It’s really competitive. I didn’t think I’d get it, as I’d just finished my bachelor’s degree, but I wanted to learn more about the application process. It was a nice surprise to receive it," says Carla.The ceremony took place in Barcelona, where the scholarship was presented directly from the hands of the King. "At the reception that followed, I was able to discuss with the Queen my In addition to her academic record, this scholarship also recognizes Carla’s social commitment, including volunteer work in India. She has also been involved in youth associations, as well as taking part in international exchanges through the European Commission.
After arriving in Quebec, Carla continued to get involved, notably through the Genetics Society of America’s International Leadership Program for the Dissemination of Science. She also won a gold medal at iGEM, a competition organized by the Massachusetts Institute of Technology (MIT), for an airborne pathogen biosensor developed with colleagues from the Faculty of Science and Engineering.
Her outstanding commitment to the scientific community and society earned her the Michèle-Auger Award 2023 . Winner of the Genetics Society of America’s DeLill Nasser Award in 2023, Carla is also a member of the Faculty of Graduate and Postdoctoral Studies Honor Roll.
What’s next for her? She’s thinking of doing a post-doc to pursue an academic career in research, combining human evolution and molecular biology. Her ideal career would be to become a professor. "I love explaining science and I can’t stop asking myself questions."
