- Author: Kathy Keatley Garvey
Well, how about nematodes? They can do "tricks," too.
Professor and plant pathology researcher Melissa Mitchum of the Department of Pathology, University of Georgia, willpresent the next UC Davis Department of Entomology and Nematology seminar.on "The Tricks Phytonematodes Use to Modulate Plant Development."
Her virtual seminar begins at 4:10 p.m., Pacific Time, on Wednesday, March 9, announced seminar coordinator and nematologist Shahid Siddique, assstant professor, UC Davis Department of Entomology and Nematology.
"Phytonematodes secrete a suite of effectors to modulate developmental programs of their hosts to cause disease," Mitchum says in her abstract. 'In this talk, I will highlight what we are learning about these effectors and the tricks they use to accomplish their goals."
Along with colleague Lisa Beamer of the University of Missouri, Mitchum is co-directing a four-year $1.2 million grant from the joint National Science Foundation and the U.S. Department of Agriculture National Institute of Food and Agriculture Plant-Biotic Interactions Program "to help combat a devastating soybean pathogen," according to a January 2022 news article in the Johnson City Press, Tenn. "The soybean cyst nematode, a microscopic roundworm, is responsible for annual crop losses of $1 billion in the U.S. alone," the news story relates.
Mitchum's research focuses "on molecular plant-nematode interactions with an emphasis on the sedentary endoparasitic cyst and root-knot nematodes," Mitchum says on her website. "Pathosystems include cyst (Heterodera glycines) nematode on soybean, cyst (Vittitadera zeaphila) nematode on corn, and root-knot (Meloidogyne spp.) nematodes on soybean, cotton, and peanut. We utilize the model plant Arabidopsis to accelerate our studies to dissect the molecular basis of parasitism by cyst (Heterodera schachtii) and root-knot nematodes. Our work addresses plant responses during compatible and incompatible plant-nematode interactions, the identification and functional analysis of nematode stylet-secreted effector proteins, and developmental reprogramming of host root cells via peptide mimicry and phytohormone manipulation. I work closely with plant breeders to develop high yielding, nematode resistant varieties. Current efforts are also focused on translating basic discoveries to develop novel approaches for nematode resistance in crop plant."
Mitchum received her bachelor's degree in biology in 1993 from the University of Puget Sound, Tacoma, Wash., and her master's degree in plant pathology from the University of Nebraska, Lincoln, in 1995. She obtained her doctorate in plant pathology, with a minor in biotechnology, from North Carolina State University, Raleigh, in 2001. Mitchum served as a postdoctoral fellow with the Developmental, Cell and Molecular Biology Group at Duke University in 2003.
For any seminar technical issues, Siddique may be reached at ssiddique@ucdavis.edu.
Want to learn the basics of nematodes, aka roundworms? Be sure to watch nematologist Steve Nadler, professor and chair of the UC Davis Department of Entomology and Nematology in this YouTube video. He delivered this presentation virtually at the 2021 UC Davis Biodiversity Museum Day. He discusses what they are and why they're important to the ecosystem.
- Author: Kathy Keatley Garvey
But newly published research by UC Davis agricultural entomologist Christian Nansen and insect physiologist Michael Strand of the University of Georgia reveals a new, non-destructive and quite accurate method to characterize physiological responses to parasitism: proximal remote sensing or body reflectance response data.
They published their research, “Proximal Remote Sensing to Non-Destructive Detect and Diagnose Physiological Response by Host Insect Larvae to Parasitism,” Dec. 4 in the journal Frontiers in Physiology.
Nansen, first author of the paper and an associate professor in the UC Davis Department of Entomology and Nematology, specializes in insect ecology, integrated pest management and remote sensing. Strand, a professor of entomology at the University of Georgia, is an international authority on the physiology of insect parasitism.
The scientists studied two common parasitic wasps or parasitoids, Microplitis demolitor, and Copidosoma floridanum, which lay their eggs in the larval stages of the soybean looper moth, Chrysodeixis includens. The pest, found throughout much of North and South America and elsewhere, feeds on soybeans.
“Based on reflectance data acquired three to five days post-parasitism, all three treatments (control larvae, and those parasitized by either M. demolitor or C. floridanum) could be classified with more than 85 percent accuracy,” they wrote.
Due to parasitism-induced inhibition of growth, “it's easy to differentiate soybean loopers parasitized by M. demolitor from non-parasitized larvae as long as the developmental stage of the host larva is known,” they said. In addition, a single M. demolitoroffspring emerges from the host larva 7-9 days post-parasitism to pupate, while non-parasitized larvae continue to increase in size to the final instar.
Copidosoma floridanum minimally alters host growth until late in the final instar, when thousands of wasp progeny complete their development. This wasp is known for having the largest recorded brood—3,055 individuals--of any parasitoidal insect.
The researchers said that the accuracy rate of more than 85 percent holds promise. “The hyperspectral proximal imaging technologies represent an important frontier in insect physiology, as these technologies can be used non-invasively to characterize physiological response across a range of time scale factors, such as minutes of exposure or acclimation to abiotic factors, circadian rhythms, and seasonal effects. Although this study is based on data from a host-parasitoid system, results may be of broad relevance to insect physiologists.”
Both of the wasps they studied are idiobionts and endoparasitoids.
Nansen noted that “many species of minute wasps are parasitoids of eggs and larvae of other insects, and parasitism represents one of the most extreme life strategies among animals”
“Living inside the body of another animal,” he said, “poses a series of non-trivial challenges, including how to overcome/suppress the defense response by the host; how to obtain oxygen; how to feed on the host without killing it--because once the host is dead, then microbial organisms and general decomposition will make the host body unsuitable--and how to manage waste.”
Nansen likened the developing parasitoids to astronauts flying in a space capsule. “A developing parasitoid faces a long list of serious practical challenges, so the evolutionary selection pressure has been immense and lead to some of the most extreme cases of co-evolution.”
And those soybean loopers? Those major pests of soybeans? Thanks to this research, we now know more about physiological responses to parasitism--and there's more to come. (We're also admiring the amazing photography of Jena Johnson!)
As the researchers said: "The hyperspectral proximal imaging technologies represent an important frontier in insect physiology."