Liming Cai is one of our 2021 Stengl-Wyer Scholars. She is a systematic biologist broadly interested in the study of phylogenetics and evolutionary genomics of plants. Her research integrates fieldwork, herbarium collections, and genomic analysis to characterize the patterns and drivers of biodiversity. As part of the Stengl-Wyer Endowment, the Stengl-Wyer Postdoctoral Scholars Program provides up to three years of independent support for talented postdoctoral researchers in the broad area of the diversity of life and/or organisms in their natural environments.
Liming graciously gave time for an interview on her background and fascinating work.
Tell us where you came from before UT, and what you studied then.
I got my BS from Fudan University, China in 2014, and then moved to Cambridge for my doctoral research on plant evolutionary biology at Harvard. After I completed my PhD in 2020, I took a postdoc position at the University of California, Riverside on plant-insect interaction. My research is always themed around plants and phylogeny. I studied the systematics of the cabbage family Brassicaceae for undergrad thesis and my doctoral research, on the other hand, gave me the opportunity to work with the most glorious group of plants in the world — Malpighiales. There are more than 16,000 species in this largely tropical clade. You might be familiar the passion fruits, rubber trees, mangroves, willows, as well as the world’s largest flower Rafflesiaceae. These astonishing diversities evolved almost overnight during the Mid-Cretaceous. I spent much of my PhD trying to resolve this ancient radiation as well as its evolutionary consequences. I found that whole genome duplications might helped many Malpighiales survive dramatic global warming; the parasitic Rafflesiaceae have a different host in Cretaceous other than the current one; and it is absolutely impossible to reconstruct a robust phylogeny for Malpighiales.
These alpine Draba (Brassicaceae) in Xingjiang made Liming as an undergrad want to be a botanist.
What got you interested in studying phylogenetics and evolutionary genomics of plants?
This goes back a long way — like many others in the department, I loved digging up soil and chasing all sorts of animals when I was a kid. I was certainly more interested in insects and mammals before I went to college. But there were several defining moments at Fudan that made me committed to plants. One was the introductory biology course I took during my freshman year. I completed an inventory report of all 152 plant species I could find in our half-acre garden with the help from the library and internet. I grew from knowing almost nothing about plant taxonomy to kind of a go-to person for identification among my peers. The other one was the fieldtrip to Xingjiang, northwest China in my sophomore. I was totally thrilled to see the cute dwarf alpine Brassicaceae and I could step on three different species simultaneously (if I was not careful). After the trip, I was pretty determined to become a botanist. In graduate school, I was exposed to very cutting-edge technologies. Applying high throughput sequencing data to systematics tells us so much more about the Tree of Life and I certainly enjoy teaching myself bioinformatics.
A specimen of broomrape (Orobanche ludoviciana) at the Billie L. Turner Plant Resources Center showing both the parasite and the host.
How do the Biodiversity Collections like the Billie L. Turner Plant Resources Center UT figure into your work?
Even before I became a scientist, I was already a huge fan of museums and natural history collections. They play such an important role in advancing education and science in every corner of the world. I am very proud to be part of the educator and researcher team as well. The specimens held at the Billie L. Turner Plant Resources Center will provide vital material for my proposed research at UT, which will explore the parasitic broomrape plants (Orobanchaceae). There are more than sixty Orobanchaceae species in Texas, the majority of which can be found in our herbarium. This provides a huge convenience for getting DNA materials without extensive fieldtrips, which is something I enjoy but is quite challenging during a pandemic.
Does Texas present a unique situation, challenge or benefit for your research?
Texas has a quite rich diversity of parasitic plants. The false foxglove and paintbrush are common wildflowers we can enjoy from spring to early fall. They are hemiparasites, meaning that while they take nutrients from their hosts, they are also photosynthetic and generate their own energy. On the other hand, if we travel to the mountainous regions in the Big Bend National Park or the desserts in the west, we can find holoparasites such as the broomrapes and American cancer-root. These plants are completely non-photosynthetic and they only emerge above ground when they are flowering. Texas is really a wonderful place to be for someone who study parasitic plants.
Where do you see your research agenda heading here at UT?
My work here will hopefully shed new light into the molecular mechanism of plant parasitism. Parasitic plants are no doubt unique existences. They feed off other plants and may not be photosynthetic. My proposed research will look at mito-nuclear coevolution in the broomrape family Orobanchaceae. Mitochondrial function and gene content are generally under strong purifying selection among flowering plants. But due to the alteration in their life history strategies, we expect such selection to be relaxed in parasites, which is reflected by higher rates of mitochondrial horizontal gene transfer. I will work with Dr. Robert K. Jansen to reconstruct mitogenomes for Orobanchaceae species to identify any changes in gene content. I will also work with Dr. Justin C. Havird to conduct physiology experiments to test whether these alterations lead to any deficiency in mitochondrial function.
Want to learn about about Liming's research? Check out a recent talk she gave called "Anything but the species tree." You can watch it here.
The independent losses of photosynthesis in Orobanchaceae provide an ideal comparative framework to study the evolutionary consequences of parasitism.
