- Author: Kathy Keatley Garvey
Today, during the 62nd annual international conference of the Society of Nematologists, being held July 9-14 in Columbus, Ohio, The Proceedings of the National Academy of Sciences (PNAS) published a UC Davis research team's important--and exciting--research paper on root-knot nematodes.
It's online at “Root-Knot Nematodes Produce Functional Mimics of Tyrosine-Sulfated Plant Peptides."
Basically, the researchers discovered that “both a harmful plant bacterium and a parasitic worm can mimic a plant peptide hormone to enhance their ability to infect plants.”
It's a joint project of nematologist Shahid Siddique, an associate professor in the Davis Department of Entomology and Nematology, and Siddique and UC Davis distinguished professor Pamela Ronald, a plant pathologist and geneticist in the Department of Plant Pathology and the Genome Center. They are the corresponding authors. Joint first-authors are Henok Zemene Yemer, formerly of the Siddique lab and now with Gingko Bioworks, Emeryville, and Dee Dee Lu of the Ronald lab.
It's like hijacking plant development to facilitate parasitism, according to Siddique. “This finding showcases an amazing case of convergent evolution across three different types of organisms, revealing how diverse life forms can develop similar strategies for survival.”
“Root-knot nematodes are a major threat to various crops, including fruit trees and vegetables,” Siddique said. “In California, tomatoes, almonds, and walnuts are among the major hosts susceptible to root-knot nematode infection.”
Siddique and UC Davis distinguished professor Pamela Ronald, a plant pathologist and geneticist in the Department of Plant Pathology and the Genome Center, are the joint corresponding authors. Joint first-authors are Henok Zemene Yemer, formerly of the Siddique lab and now with Gingko Bioworks, Emeryville, and Dee Dee Lu of the Ronald lab.
Plant-parasitic nematodes (PPNs) are among the most destructive plant pathogens, causing an annual economic loss of $8 billion to U.S. growers and more than $100 billion worldwide, the authors said.
The team also included emerita professor Valerie Williamson of the former Department of Nematology; Maria Florencia Ercoli, postdoctoral fellow in the Ronald lab; Alison Coomer Blundell, a doctoral candidate in the Siddique lab; and Paulo Vieira of the USDA's Mycology and Nematology Genetic Diversity and Biology Laboratory, Beltsville, Md.
“Plant peptides containing sulfated tyrosine (PSY)-family peptides are peptide hormones that promote root growth via cell expansion and proliferation,” the authors explained. “A PSY-like peptide produced by a bacterial pathogen has been shown to contribute to bacterial virulence. Here, we discovered that PSY-like peptides are encoded by a group of plant-parasitic nematodes known as root-knot nematodes. These nematode-encoded PSY mimics facilitate the establishment of parasitism in the host plant. Our findings are an example of a functional plant peptide mimic encoded by a phytopathogenic bacterium (prokaryote) and a plant-parasitic nematode (an animal).”
The project drew financial support from a collaborative grant awarded to Siddique and Ronald from the National Science Foundation's Division of Integrative Organismal Systems.
Siddique, a member of the UC Davis faculty since 2019, focuses his research on basic as well as applied aspects of interaction between parasitic nematodes and their host plants. “The long-term object of our research is not only to enhance our understanding of molecular aspects of plant–nematode interaction but also to use this knowledge to provide new resources for reducing the impact of nematodes on crop plants in California.”
Ronald, noted for her innovative work in crop genetics, especially rice, is recognized for her research in infectious disease biology and environmental stress tolerance. Thomson Reuters named her one of the world's most influential scientific minds and Scientfic American recognized her as among the world's 100 most influential people in biotechnology. In 2022 Ronald received the Wolf Prize in Agriculture.
The next steps? “Currently, we are working to understand the mechanism by which these peptides contribute to the nematode infection,” Siddique said. “This entails the characterization of receptors involved and gaining insights into transcriptional changes.”
![An illustration from the PNAS paper: Rice infected by root-knot nematodes (stained in red). (Illustration by Shahid Siddique) An illustration from the PNAS paper: Rice infected by root-knot nematodes (stained in red). (Illustration by Shahid Siddique)](/blogs/blogcore/blogfiles/100611.jpg)
- Author: Kathy Keatley Garvey
The research, “Root-Knot Nematodes Produce Functional Mimics of Tyrosine-Sulfated Plant Peptides,” is published in the current edition of the Proceedings of the National Academy of Sciences (PNAS).
It's like hijacking plant development to facilitate parasitism, according to nematologist Shahid Siddique, an associate professor in the Davis Department of Entomology and Nematology and one of the corresponding authors of this study. “This finding showcases an amazing case of convergent evolution across three different types of organisms, revealing how diverse life forms can develop similar strategies for survival.”
The root-knot nematode, which threatens global food security, is a small worm-like organism that is a highly evolved obligate parasite, or an organism that cannot survive without its host. It is known to infest some 2000 crops worldwide. “These parasites have a remarkable ability to establish elaborate feeding sites in roots, which are their only source of nutrients throughout their life cycle,” the authors wrote.
“Root-knot nematodes are a major threat to various crops, including fruit trees and vegetables,” Siddique said. “In California, tomatoes, almonds, and walnuts are among the major hosts susceptible to root-knot nematode infection.”
Siddique and UC Davis distinguished professor Pamela Ronald, a plant pathologist and geneticist in the Department of Plant Pathology and the Genome Center, are the joint corresponding authors. Joint first-authors are Henok Zemene Yemer, formerly of the Siddique lab and now with Gingko Bioworks, Emeryville, and Dee Dee Lu of the Ronald lab.
The team also included emerita professor Valerie Williamson of the former Department of Nematology; Maria Florencia Ercoli, postdoctoral fellow in the Ronald lab; Alison Coomer Blundell, a doctoral candidate in the Siddique lab; and Paulo Vieira of the USDA's Mycology and Nematology Genetic Diversity and Biology Laboratory, Beltsville, Md.
“Plant peptides containing sulfated tyrosine (PSY)-family peptides are peptide hormones that promote root growth via cell expansion and proliferation,” the authors explained. “A PSY-like peptide produced by a bacterial pathogen has been shown to contribute to bacterial virulence. Here, we discovered that PSY-like peptides are encoded by a group of plant-parasitic nematodes known as root-knot nematodes. These nematode-encoded PSY mimics facilitate the establishment of parasitism in the host plant. Our findings are an example of a functional plant peptide mimic encoded by a phytopathogenic bacterium (prokaryote) and a plant-parasitic nematode (an animal).”
The research involved gene expression analysis and parasitism of tomato and rice plants.
The project drew financial support from a collaborative grant awarded to Siddique and Ronald from the National Science Foundation's Division of Integrative Organismal Systems.
Siddique, a member of the UC Davis faculty since 2019, focuses his research on basic as well as applied aspects of interaction between parasitic nematodes and their host plants. “The long-term object of our research is not only to enhance our understanding of molecular aspects of plant–nematode interaction but also to use this knowledge to provide new resources for reducing the impact of nematodes on crop plants in California.”
Ronald, noted for her innovative work in crop genetics, especially rice, is recognized for her research in infectious disease biology and environmental stress tolerance. Thomson Reuters named her one of the world's most influential scientific minds and Scientfic American recognized her as among the world's 100 most influential people in biotechnology. In 2022 Ronald received the Wolf Prize in Agriculture.
The next steps? “Currently, we are working to understand the mechanism by which these peptides contribute to the nematode infection,” Siddique said. “This entails the characterization of receptors involved and gaining insights into transcriptional changes.”
![An illustration from the PNAS paper: Rice infected by root-knot nematodes (stained in red). (Illustration by Shahid Siddique) An illustration from the PNAS paper: Rice infected by root-knot nematodes (stained in red). (Illustration by Shahid Siddique)](/blogs/blogcore/blogfiles/100579.jpg)
- Author: Kathy Keatley Garvey
Kaloshian will speak on "Root-Knot Nematode Perception and Immune Signaling in Arabidopsis" at a hybrid seminar, both in-person and virtual, at 4:10 p.m., Wednesday, June 1 in 122 Briggs Hall. The Zoom link is https://ucdavis.zoom.us/j/99515291076.
Kaloshian will discuss her recent research, "A G-lectin Receptor Kinase is a Negative Regulator of Arabidopsis Immunity Against Root-Knot Nematode Meloidogyne incognita," published in bioRxiv in October 2021. She and her colleagues found that "A plasma membrane localized G-lectin receptor kinase acts as a negative immune regulator by interfering with defense responses activated by nematode and microbial elicitors."
"Root-knot nematodes (Meloidogyne spp., RKN) are responsible for extensive crop losses worldwide," she and her colleagues wrote in their abstract. "For infection, they penetrate plant roots, migrate between plant cells, and establish feeding sites, known as giant cells, in the root pericycle. Previously, we found that nematode perception and early plant responses were similar to those for microbial pathogens and require the BAK1 co-receptor in Arabidopsis thaliana and tomato. To identify additional receptors involved in this process, we implemented a reverse genetic screen for resistance or sensitivity to RKN using Arabidopsis T-DNA alleles of genes encoding transmembrane receptor-like kinases. This screen identified a pair of allelic mutations with enhanced resistance to RKN in a gene we named ENHANCED RESISTANCE TO NEMATODES 1 (ERN1). ERN1 encodes a G-type lectin receptor kinase (G-LecRK) with a single pass transmembrane domain. Further characterization showed that ern1 mutants displayed stronger activation of MAP kinases, elevated levels of the defense marker MYB51, and enhanced H202 accumulation in roots upon RKN elicitor treatments. Elevated MYB51expression and ROS burst were also observed in leaves of ern1 mutants upon flg22 treatment. Complementation of ern1.1 with 35S- or native promotor-driven ERN1 rescued the RKN infection and enhanced defense phenotypes. Taken together, our results indicate that ERN1 is an important negative regulator of immunity."
Kaloshian, who joined the UC Riverside faculty in 1997 and chaired the Department of Nematology from 2017-2021, was named divisional dean on July 1, 2021. During her three-year term, she is overseeing four departments: Botany and Plant Sciences, Entomology, Environmental Sciences, and Nematology.
As a molecular geneticist, Kaloshian studies the interactions between plants and nematodes, and insect pests. Her grants have been funded by the National Institute of Food and Agriculture and the National Science Foundation. She has served as a senior editor of journals in her field of research. (See UC Riverside news story)
Kaloshian is a fellow of the American Association for the Advancement of Science and a recipient of the Syngenta Award for Excellence in Research from the Society of Nematologists. Her other honors include the Chancellor's Award for Excellence in Undergraduate Research and Creative Achievement, and the UC Riverside Distinguished Service Award for her development of the COVID-19 campus testing lab.
Kaloshian holds a bachelor of science degree in agricultural engineering and master's degree in plant protection from American University of Beirut. She obtained her doctorate in plant pathology from UC Riverside and completed her postdoctoral training at UC Davis.
Hosting the seminar is coordinator Shahid Siddique, assistant professor, UC Davis Department of Entomology and Nematology. For any technical issues, contact him at ssiddique@
- Author: Kathy Keatley Garvey
The nematode collection featured mostly root-knot nematodes and Ascaris (roundworm) nematodes. The display included:
- What's in the jar?
- Celery infected with root-knot nematodes
- Tree swallow infected with Diplotriaena
- White-tailed deer eye infected with a Thelazia species
- Peach root infected with root-knot nematodes
- Mormon crickets infected with Gordius robustus
- Lettuce infected with root-knot nematodes
- Garlic damaged by Ditylenchus dipsaci
- Horse stomach infected with three parasites: Parascaris (roundworms), tapeworms, and botfly larvae.
- Grape roots infected with root-knot nematodes
- Sweet potato infected with root-knot nematodes
- Sugar beet infected with cyst nematodes
- Peach root infected with cyst nematodes
- Sugar beet infected with root-knot nematodes
- Ascaris lumbricoides (roundworm)
- Minke whale infected infected with ascaridoid nematodes
- Heartworm of dog
"Plant-parasitic nematodes are destructive pests causing losses of billions of dollars annually," Siddique says on his website. "Economic, health, and environmental considerations make natural host plant resistance a preferred strategy for nematode control, but there are limitations to this approach. In many cases, the resistance conferred by resistance genes is partial, and some of the nematodes are able to survive. Similarly, nematode resistance genes are often effective against only one or a few species, whereas plants are exposed to several pathogens in the field. Another concern is the emergence of pathotypes that can overcome resistance. In view of all these limitations, it is important to identify additional mechanisms and tools that can be used to develop novel and sustainable approaches to the management of nematodes."
Research in the Siddique lab focuses on basic as well as applied aspects of interaction between parasitic nematodes and their host plants, he says. "The long-term object of our research is not only to enhance our understanding of molecular aspects of plant–nematode interaction but also to use this knowledge to provide new resources for reducing the impact of nematodes on crop plants in California."
Nematologist Steve Nadler, professor and chair of the UC Davis Department of Entomology and Nematology, explains what a nematode is on this YouTube video that he presented at last year's UC Davis Biodiversity Museum Day. Due to COVID-19 precautions, the 2021 event was virtual, instead of in-person.
Visitors to the 2022 UC Davis Biodiversity Museum Day adhered to the Campus Ready guidelines, with masks required. Eleven museums or collections participated:
- Arboretum and Public Garden
- UC Davis Bee Haven
- Bohart Museum of Entomology
- Botanical Conservatory
- California Raptor Center
- Center for Plant Diversity
- Department of Anthropology Museum
- Museum of Wildlife and Fish Biology
- Nematode Collection
- Paleontology Collection
- Phaff Yeast Culture Collection
In addition, visitors could register for side trips to the Arboretum and Public Garden, Bee Haven and Phaff Yeast Culture Collection. The Botanical Conservatory opened its doors to visitors throughout the day.
Traditionally, the UC Davis Biodiversity Museum Day takes place the Saturday of Presidents' Weekend, and at the individual locations, noted organizer Tabatha Yang, education and outreach coordinator. This year it occurred at one site, exposition-style.
The campus is now gearing up for the 108th annual UC Davis Picnic Day, set April 23 and themed "Rediscovering Tomorrow." The free public event is the first, in-person Picnic Day in two years.
![Three nematologists kept busy at their booth at the UC Davis Biodiversity Museum Day. In front is coordinator Shahid Siddique, assistant professor, and his doctoral students Pallavi Shakya (nearest him) and Alison Coomer. In the back (far right) is Rob Blundell, not part of the lab, but who assisted. (Photo by Kathy Keatley Garvey) Three nematologists kept busy at their booth at the UC Davis Biodiversity Museum Day. In front is coordinator Shahid Siddique, assistant professor, and his doctoral students Pallavi Shakya (nearest him) and Alison Coomer. In the back (far right) is Rob Blundell, not part of the lab, but who assisted. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/89473.jpg)
![Nematologist Shahid Siddique, assistant professor, UC Davis Department of Entomology and Nematology, shows nematodes to curious visitors. (Photo by Kathy Keatley Garvey) Nematologist Shahid Siddique, assistant professor, UC Davis Department of Entomology and Nematology, shows nematodes to curious visitors. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/89474.jpg)
![UC Davis doctoral student and nematologist Pallavi Shakya answers questions about nematodes. (Photo by Kathy Keatley Garvey) UC Davis doctoral student and nematologist Pallavi Shakya answers questions about nematodes. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/89475.jpg)
![Doctoral student and nematologist Alison Coomer fields questions from the crowd. At far right is scientist Rob Blundell, who assisted. (Photo by Kathy Keatley Garvey) Doctoral student and nematologist Alison Coomer fields questions from the crowd. At far right is scientist Rob Blundell, who assisted. (Photo by Kathy Keatley Garvey)](/blogs/blogcore/blogfiles/89476.jpg)
- Author: Kathy Keatley Garvey
The display will include:
- What's in the jar?
- Celery infected with root-knot nematodes
- Tree swallow infected with Diplotriaena
- White-tailed deer eye infected with a Thelazia species
- Peach root infected with root-knot nematodes
- Mormon crickets infected with Gordius robustus
- Lettuce infected with root-knot nematodes
- Garlic damaged by Ditylenchus dipsaci
- Horse stomach infected with three parasites: Parascaris (roundworms), tapeworms, and botfly larvae.
- Grape roots infected with root-knot nematodes
- Sweet potato infected with root-knot nematodes
- Sugar beet infected with cyst nematodes
- Peach root infected with cyst nematodes
- Sugar beet infected with root-knot nematodes
- Ascaris lumbricoides (roundworm)
- Minke whale infected infected with ascaridoid nematodes
- Heartworm of dog
The event is set for 11 a.m. to 3 p.m. in the UC Davis Conference Center, 555 Alumni Lane. Admission and parking are free, but visitors must adhere to the COVID-19 Campus Ready guidelines. Masks will be required in accordance with campus policies, organizers said. Visitors can also sign up at the Conference Center for limited tours. Several museums or collections will be offering tours. (See news story)
"Plant-parasitic nematodes are destructive pests causing losses of billions of dollars annually," Siddique says on his website. "Economic, health, and environmental considerations make natural host plant resistance a preferred strategy for nematode control, but there are limitations to this approach. In many cases, the resistance conferred by resistance genes is partial, and some of the nematodes are able to survive. Similarly, nematode resistance genes are often effective against only one or a few species, whereas plants are exposed to several pathogens in the field. Another concern is the emergence of pathotypes that can overcome resistance. In view of all these limitations, it is important to identify additional mechanisms and tools that can be used to develop novel and sustainable approaches to the management of nematodes."
"Research in the Siddique lab focuses on basic as well as applied aspects of interaction between parasitic nematodes and their host plants," Siddique points out on his website. "The long-term object of our research is not only to enhance our understanding of molecular aspects of plant–nematode interaction but also to use this knowledge to provide new resources for reducing the impact of nematodes on crop plants in California."
Coomer, a second-year doctorate student, recently won a worldwide competition competition sponsored by the International Federation of Nematology Societies (IFNS) for her three-minute thesis on root-knot nematodes. She delivered her video presentation virtually on “Trade-Offs Between Virulence and Breaking Resistance in Root-Knot Nematodes.” She will be awarded a busary and plaque at the 7th International Congress of Nematology (ICN), set May 1-6 in Antibes, France.
Coomer earlier was selected one of the nine finalists in the 22-participant competition, vying against eight other graduate students from the University of Idaho, Moscow; and universities in England, Australia, Brazil, Ireland, Kenya, Belgium and South Africa.
The UC Davis Biodiversity Museum Day is traditionally held on the Saturday of Presidents' Day weekend. However, last year's event was virtual, and this year's event is centrally located in an exposition. For more information, access the UC Davis Biodiversity Museum Day website and/or connect with Instagram,Twitter, and Facebook.
![A juvenile root-knot nematode (Meloidogyne incognita) penetrates a tomato root. (USDA Photo) A juvenile root-knot nematode (Meloidogyne incognita) penetrates a tomato root. (USDA Photo)](/blogs/blogcore/blogfiles/89357.jpg)
![Nematologist Steve Nadler, professor and chair of the UC Davis Department of Entomology and Nematology, talks about nematodes in this YouTube video. Nematologist Steve Nadler, professor and chair of the UC Davis Department of Entomology and Nematology, talks about nematodes in this YouTube video.](/blogs/blogcore/blogfiles/89361.jpg)