Faculty Spotlight – Ben Parker and the Parker Lab
Walking into Ben Parker’s lab, you are greeted by rows upon rows of small plants, each in their own enclosed container with a complex handwritten label. What initially looks like a greenhouse operation changes quickly when you look closely at the plants: each is covered by hundreds of tiny bugs, or pea aphids.
Parker’s lab utilizes the pea aphid as a model organism to study its life history traits and genetics and uses the findings to further understand larger questions in biology, evolutionary biology, and microbiology. The pea aphid system offers two main advantages: the insects give live birth to genetically identical offspring in just 10 days, and their bodies contain a simple microbial community, allowing Parker and his researchers to easily add or remove microbes in the systems and complete various mechanistic studies.
Bacteria are one microbe that inhabit aphids. They are vertically transmitted, which means they are passed from parents to offspring, and can form important symbiotic relationships with their hosts.
“The bacteria Regiella insectcola makes aphids resistant to the fungal pathogen Pandora neoaphidis,” Parker elaborates. “Not all aphids harbor Regiella, but those that do are more resistant to fungal infections.”
However, the bacteria are not entirely beneficial.
“One big question we are interested in is how the aphid’s immune system evolves to accommodate these beneficial bacteria in ways that still allow it to fight off bacterial pathogens,” Parker says.
For example, the lab has been focusing on the phenoloxidase mechanism, which is an enzyme aphids use in melanization (a method insects use to fight pathogenic microbes). Aphids harboring Regiella have reduced gene expression of the phenoloxidase enzyme producing genes.
The lab theorizes that this occurs because the bacteria are attempting to maximize their abundance, despite compromising the aphid’s ability to fight off other bacteria, but this finding is just a first glimpse into the mechanism.
“We want to understand that in a broader context,” Parker states. “We want to know what effects that has on interactions with pathogenic bacteria and how those mechanisms are evolving in natural populations.”
Viral genes are also vertically transmitted between aphid parents and their offspring. One such gene has interesting morphological effects on the host wherein in two genetically identical offspring, one can be winged while the other is wingless.
This occurrence is an example of a phenotypically plastic traits, or a morphological trait influenced by the environment. In this case, the environmental trait influencing gene expression is plant crowdedness, which aphids have evolved to sense. The viral gene triggers the production of winged offspring by making aphids more sensitive to crowding.
“When it is too crowded, they produce winged offspring, so they can fly to another plant and start over,” Parker explains.
Currently, the Parker lab is focusing their studies on the genome and microbiome of the Pandora neoaphidis fungal pathogen. Additionally, they are working to understand aphid immune systems and how different aphid genotypes interact with bacteria. This talented group undoubtedly has a promising future.
-By Taylor Mattioli