His seminar, to be both in-person and virtual, begins at 4:10 p.m., Pacific Time in 122 Briggs Hall. The Zoom link is https://ucdavis.zoom.us/j/99515291076.
"From the moment of initial encounter with an insect herbivore, a suite of inducible plant defenses are triggered; however, the molecular mechanisms for recognition and response are not highly studied," Steinbrenner writes in his abstract. "Specific molecular patterns from insects can serve as elicitors of defense responses on host plants, but precise receptors mediating such responses have remained elusive. We recently identified a cell surface receptor, Inceptin Receptor (INR), which detects a set of ubiquitous peptide fragments found in the oral secretions of Lepidopteran larval herbivores. INR is specific to select legume species and may structure insect host range across this plant family. We hypothesize that INR serves as a recently evolved and highly potent mechanism to perceive a specific danger signal, above and beyond cues associated with generic tissue damage. I will discuss our recent transcriptiomic characterization of inceptin responses in bean and cowpea, highlighting strong anti-herbivore defense outputs which occur after inceptin treatment but not wounding alone. I will also compare plant responses to herbivory with well-characterized pathways mediating recognition of microbial pathogens."
Steinbrenner focuses his research on cell and molecular biology, genetics and genomics, and plant biology. He holds a bachelor of science degree in biology from Tufts University (2010) and a doctorate from UC Berkeley in plant biology (2015). He was awarded a Howard Hughes Medical Institute Postdoctoral Fellowship of $180,000 in 2016 and studied with Eric Schmelz at UC San Diego.
The Steinbrenner lab studies the molecular bases of plant immunity to pathogens and pests. "We are specifically interested in recognition and signaling functions of cell surface receptors and evolutionary processes driving novel immune specificity," he says on his website.
Steinbrenner served as the lead author of a paper published Nov. 23, 2021 in the Proceedings of the National Academy of Sciences on how cowpea plants detect that they're being eaten by caterpillars. In the article, A Receptor-Like Protein Mediates Plant Immune Responses to Herbivore-Associated Molecular Patterns, scientists from the University of Washington and UC San Diego reported that the cowpea plants harbor receptors on the surface of their cells that can detect a compound in caterpillar saliva and initiate anti-herbivore defenses.
"Despite chemical controls, crop yield losses to pests and disease generally range from 20-30 percent worldwide," Steinbrenner related in a University of Washington news release. "Yet many varieties are naturally resistant or immune to specific pests. Our findings are the first to identify an immune recognition mechanism that sounds the alarm against chewing insects.”
Wrote UW science writer James Urton: "The team showed that, in response to both leaf wounds and the presence of a protein fragment specific to caterpillar saliva, the cowpea's INR protein boosts the production of ethylene, a hormone that plants often produce in response to munching by herbivores and other types of environmental stress. The protein fragment in caterpillar spit that elicited this response, Vu-IN, is actually a fragment of a cowpea protein, which gets broken down by the caterpillar as it dines on cowpea leaves." (See full article.)
Nematologist Shahid Siddique, assistant professor, UC Davis Department of Entomology and Nematology, coordinates the Wednesday seminars. For any Zoom technical issues, contact him at firstname.lastname@example.org.
A first-generation college student, Rajarapu holds two biochemistry degrees from Osmania University, India: her bachelor's degree (2006) and her master's degree (2008). She obtained her doctorate in entomology in 2013 from The Ohio State University, working with Professors Daniel Herms and Larry Phelan. Her dissertation: "Integrated Omics on the Physiology of Emerald Ash Borer."
“I am interested in understanding and predicting how microbial communities influence interactions between plants and insects,” she said. “In the Vannette lab (in Briggs Hall), we use tools and concepts from microbial ecology, chemical ecology, and community ecology to better understand the ecology and evolution of interactions among plants, microbes and insects."
A native of Hudsonville, Mich., Vannette received her bachelor of science degree in biology with honors at Calvin College, Grand Rapids, Mich., and her doctorate in ecology and evolutionary biology from the University of Michigan, in 2011. Her dissertation was entitled “Whose Phenotype Is It Anyway? The Complex Role of Species Interactions and Resource Availability in Determining the Expression of Plant Defense Phenotype and Community Consequences.”
In her PhD research, she examined how variation in nutrient availability and plant associations with mycorrhizal fungi belowground influenced defense chemistry in milkweed plants and the performance of a specialist herbivore (Danaus plexippus). She found that resource-based tradeoffs can in part explain plant allocation to antiherbivore defense and mycorrhizal fungi. This work also describes that plant genotypes vary in their investment in defense and associations with belowground fungi.
As a Stanford University postdoctoral fellow, funded by a life sciences research fellowship, Vannette examined the community ecology of plant-associated microorganisms. Using diverse systems, she studied the assembly of microbial communities, microbial response to anthropogenic changes like habitat fragmentation, and microbial effects on plant-pollinator interactions.
- Community ecology of plant-associated microbial communities. She explored what mechanisms shape the structure and function of microbial communities associated with plants, and how to assemble mechanisms to better understand functions, including the effects on insect herbivores and pollinators. She also researched how ants influence microbial community structure and nectar characteristics in coffee agroecosystems.
- Nectar ecology. Knowing that yeasts and bacteria are common inhabitants of flowers, and attain high densities in floral nectar, she researched how these microbes influence plants and pollinators, the mechanisms involved, and evolutionary ecology of these interactions. She also studied how nectar constituents influence pollinator foraging and health.
- Influence of anthropogenic changes on plant-microbe (insect) interactions. She researched how fragmentation affects fungal community composition in the rhizosphere of Meterosideros polymorpha, a species of flowering evergreen tree in the myrtle family. She also studied elevated carbon dioxide changes plant-microbe-insect interactions, and researched the effects of mycorrhizal fungi on plant defense and plant-herbivore interactions.
The National Wildlife Research Foundation featured Vannette's research on monarchs and milkweed in its March 11, 2013 piece on “Catering to Butterfly Royalty." The article, by author Doreen Cubie, focused on Vannette's research as a graduate student at the University of Michigan. Vannette and advisor Mark Hunter studied five common species of milkweeds, the host plant for monarchs. They found that climate change may disrupt the chemistry of milkweeds, and encouraged gardeners to help the monarchs by planting more of these critical host plants.
Vannette and Hunter grew the plants in open-air chambers, “exposing them to elevated amounts of carbon dioxide designed to mimic Earth's atmosphere in the future,” wrote Cubie. “Although most of the plants grew slightly larger, the composition of plant leaves changed dramatically. Most of the milkweed families decreased their production of toxins, some by as much as 50 percent. The extra carbon dioxide exposure toughened the leaves, a problem for the caterpillars.
Last March Vannette was an invited speaker on the ecology and evolution of the microbiome at the University of Michigan Early Career Scientists' symposium in Ann Arbor, Mich.
Among her recent publications:
- Co-author of “Plant-Derived Variation in the Composition of Aphid Honeydew and its Effects on Colonies of Aphid-Tending Ants,” published in November 2014 in the journal Ecology and Evolution.
- Lead author of “Genetic Variation in Plant Below-Ground Response to Elevated CO2 and Two Herbivore Species,” published in July 2014 in Plant Soil.
- Co-author of “Honey Bees Avoid Nectar Colonized by Three Bacterial Species, but not by a Yeast Species, Isolated from the Bee Gut,” published in a January 2014 edition of PLOS ONE.
- Lead author of “Historical Contingency in Species Interactions: Towards Niche-Based Predictions,” published November 2013 in Ecology Letters. (Recommended by the Faculty of 1000)