Healthy and diseased silene acaulis.
Healthy and diseased silene acaulis. Photo courtesy of Michael Hood

When it comes to disease, plants are the perfect research subjects. They can be crowded into close quarters. They can be grown quickly and in large numbers. Associate Professor of Biology Michael E. Hood admires them, but he doesn’t feel badly when he destroys a diseased specimen.

All in all, plants are perfect if, like Hood and his students, you want to study large swaths of diseases—particularly in sexually transmitted forms—and how they spread among individuals.

“From a practical standpoint, plant systems in general often work much better than animal systems for studying disease resistance or disease transmission,” notes Victoria Luizzi ’17, who has been working with Hood this fall. With a thesis that involves 10,000 individual specimens, Luizzi notes that working with plants allow for “experiments on a much larger scale than is usually possible working with animals. 

This work—tracking disease among plants—this fall earned Hood (and his fellow researchers at the University of California Berkley and the University of Virginia) a $1.7 million joint grant. Issued by the National Institute of General Medical Sciences, it will fund research that could eventually lead to an understanding of a range of pathogens—including human-related ones—and the larger patterns of how they spread.

“All organisms get diseases—and the majority of species on the planet are parasites or pathogens,” says Hood. Disease “causes huge amounts of human misery and loss of life [and] greatly impacts our ability produce food and fiber that we need through agriculture. What our ultimate aims are is better understanding of these interactions.”

For the study, Hood and his students filled the McGuire Life Sciences Building greenhouse with trays of Dianthus, a relative of carnations. The plant is a common roadside weed in Italy, where Hood and his students travel each summer to study the plant in the wild. 

What our current research grant is getting at is how the disease transmits from host to host, how the disease moves from one individual to another.

When they bloom, the plants produce a pink flower about the size of a quarter. But Hood is interested in those flowers that appear dusted with grey—an indication that the plant is infected with the anther smut fungus. While the disease can be spread between neighboring plans, it also migrates from host to host by growing among the plant’s cells and replacing pollen with fungal spores. Through pollinators, these spores act as a flora version of a sexually transmitted disease.

“I could say that it’s a model for sexually transmitted diseases for plants,” but the model actually has much larger ramifications, says Hood. “It’s used as a model for sexually transmitted diseases in all types of organisms.”

This combination of factors—a subject that’s easy to manage on a large scale, a particular disease that’s safe for researchers to handle, and a fungus that spreads in  various ways—mean that the infected plants are a perfect model for researching how infections spread through large populations. 

“There’s been very little work done on under what conditions would you expect a disease to change transmission mode between, say, sexual transmission and ordinary contact transmission,” says Hood. “What our current research grant is getting at is how the disease transmits from host to host, how the disease moves from one individual to another.”

Although not part of the scope of the current project, over the long-term, such research might help create models for epidemics in humans—models that would be in understanding the spread of complex viruses with different transmission modes, such as Zika or Ebola.