About

Clare Casteel is an Associate Professor in the School of Integrative Plant Science, specializing in plant-microbe interactions, virology, and plant-virus-vector interactions. Her primary research goal is to identify the functions of microbes in plant-insect interactions and elucidate the key molecular mechanisms responsible for these relationships. Her lab focuses on pathogenic microbes and understanding how they counter plant defenses within complex communities involving insects, as well as leveraging beneficial microbes and microbiomes to mitigate the negative impacts of climate change through healthy agroecosystems and microbe engineering. Her work emphasizes viruses, aphids, diversified vegetables, organic agriculture, and climate resilience. Dr. Casteel has contributed significantly to understanding how microbes influence plant health and pest interactions, with recent research exploring the molecular mechanisms of plant-insect-virus interactions and the role of microbes in climate resilience. She has received numerous awards, including the 2023 Mid-Career Award from the Plant Genome Research Program and the 2018 Early Career Award from the same program. Her academic background includes a PhD in Plant Biology from the University of Illinois, a Master of Science from the University of California, Riverside, and a Bachelor of Science from the University of Missouri. She has taught courses on molecular biology of plant-microbe interactions and plant interactions seminar, and her research has been published in various scientific journals.

Research topics

• Biology
• Genetics
• Botany
• Ecology
• Microbiology
• Cell biology
• Computational biology
• Virology
• Agronomy

Selected publications

• Cereal rye ( <scp> <i>Secale cereale</i> </scp> ) and canola ( <scp> <i>Brassica napus</i> </scp> ) cover crops reduce dry bean ( <scp> <i>Phaseolus vulgaris</i> </scp> ) herbivore damage

  Pest Management Science · 2026-04-18

  articleSenior author

  BACKGROUND: Cover crops can support soil health and increase habitats for beneficial insects in diverse cropping systems. The aim of this study was to evaluate the impact of cover crop-conditioned soil on plant defense responses and insect pest damage using dry bean (Phaseolus vulgaris L.) as a model. RESULTS: In a 2-year, multi-location field experiment comparing four cover crop treatments and a tilled control, we found that dry beans no-till planted into mechanically terminated cereal rye (Secale cereale L.) and canola (Brassica napus L.) experienced less insect damage than controls. In the laboratory, microbiome extracts from canola-enriched field soil increased dry bean jasmonic acid levels and reduced cowpea aphid (Aphis craccivora Koch) survival compared with other soil microbiome extracts. No differences in defense hormones were detected for dry bean grown in cereal rye soil microbiome extracts, however aphid survival was reduced on these plants compared to the controls. CONCLUSIONS: Cereal rye and canola cover crops reduced insect damage in dry bean fields. Soil microbiomes associated with canola enhanced defense-related compounds in dry bean, suggesting a potential mechanism for pest suppression in the field. However, the impacts of canola varied across microbiome sources, highlighting the need for additional studies. © 2026 Society of Chemical Industry.

  PublisherDOI

• Insights Into Virus‐Encoded <scp>RNA</scp> Silencing Suppressors Across Viral Families: A Focus on Viruses Infecting Solanaceae Crops

  Physiologia Plantarum · 2026-03-01

  articleOpen access

  Viral suppressors of RNA silencing (VSRs) are proteins that interfere with antiviral defense mechanisms and enhance infection. For plant viruses, VSRs can be encoded in viral genomes and satellite molecules and play an important role in the virus's life cycle and in overcoming host defenses. However, a comprehensive review on the multifunctionality of VSRs and their role in the worldwide spread of plant viral diseases has not been performed. Here, we aim to synthesize the current understanding of the role of VSRs in the pathogenesis of Solanaceous plants, a family that includes many crops and medicinal plants. We focus on three key areas: (1) the diversity of VSRs and the mechanisms used to suppress antiviral defense, (2) the role of VSRs in viral pathogenesis beyond interfering with host RNA-silencing, and (3) the coevolution between VSRs and plant host proteins. Additionally, we describe how VSRs promote the development of diseases by altering various steps in viral pathogenicity via induction of counter-defense mechanisms. Specifically, a substantial body of evidence suggests that VSRs induce the suppression of antiviral silencing, abrogation of phytohormone signaling, and downregulation of R-gene-mediated host defense. Furthermore, we discuss how identifying and characterizing novel interactions between VSRs and Solanaceous host factors may be leveraged for developing sustainable pathogen and pest management strategies.

  PublisherDOI

• Comprehensive transcriptomic analysis reveals turnip mosaic virus infection and its aphid vector Myzus persicae cause large changes in gene regulatory networks and co-transcription of alternative spliced mRNAs in Arabidopsis thaliana

  BMC Plant Biology · 2025-01-30 · 4 citations

  articleOpen access

  BACKGROUND: Virus infection and herbivory can alter the expression of stress-responsive genes in plants. This study employed high-throughput transcriptomic and alternative splicing analysis to understand the separate and combined impacts on host gene expression in Arabidopsis thaliana by Myzus persicae (green peach aphid), and turnip mosaic virus (TuMV). RESULTS: By investigating changes in transcript abundance, the data shows that aphids feeding on virus infected plants intensify the number of differentially expressed stress responsive genes compared to challenge by individual stressors. This study presents evidence that the combination of virus-vector-host interactions induces significant changes in hormone and secondary metabolite biosynthesis, as well as downstream factors involved in feedback loops within hormone signaling pathways. This study also shows that gene expressions are regulated through alternative pre-mRNA splicing and the use of alternative transcription start and termination sites. CONCLUSIONS: These combined data suggest that complex genetic changes occur as plants adapt to the combined challenges posed by aphids and the viruses they vector. This study also provides more advanced analyses that could be used in the future to dissect the genetic mechanisms mediating tripartite interactions and inform future breeding programs.

  PublisherOA PDFDOI

• Sustainable soil management practices are associated with increases in crop defense through soil microbiome changes

  npj Sustainable Agriculture · 2025-12-22

  articleOpen accessSenior author

  Abstract Soil microbiomes regulate critical ecosystem functions, yet their relationship with agronomic practices and farmer beliefs remains unclear. Through surveying 85 organic farms, we identified five practices that reshaped soil microbiomes and linked these changes to plant defense functions. Compost and organic pesticide use were associated with decreased levels of two plant defense compounds, jasmonic and salicylic acid, while targeted irrigation, grass cover crops, and no tillage were linked to increased jasmonic acid, through changes in three microbial taxa ( Fusarium chlamydosporum ; Paenibacillus senegalensis ; Microtrichales spp.) and two beta diversity metrics. Structural equation modeling suggested no tillage, pesticide, and compost use were influenced by farmers’ beliefs in the microbiome, while adoption of targeted irrigation and grass cover crops was shaped by abiotic and economic factors. Our work indicates that soil microbiomes and their ecosystem services can be managed through farming practices and highlights sustainable pest management strategies to prioritize for outreach programs.

  PublisherOA PDFDOI

• Transcriptomic analysis reveals vector attraction to potato virus Y is mediated through temporal regulation of TERPENE SYNTHASE 1 (TPS1)

  Plant Stress · 2025-04-28 · 2 citations

  articleOpen accessSenior authorCorresponding

  • Virus-plant dynamics change over time, influencing plant-vector interactions. • Aphid vectors prefer potato virus Y (PVY) infected plants early in infection but not at later timepoints. • PVY temporally regulates transcriptional pathways related to plant defense responses and volatile organic compounds. • PVY induction of TERPENE SYNTHASE 1 early in infection is required for increased aphid preference. Viruses alter plant traits over time, which can further influence interactions between plants and insect vectors that transmit those viruses. However, the signaling pathways and regulators that control these temporal responses remain largely unknown. In this study, we used insect performance and preference bioassays, RNA-seq, and genetic tools to identify underlying mechanisms mediating temporal variation in plant-virus-vector interactions. We show that settlement and fecundity of the aphid vector, Myzus persicae , is increased on potato virus Y (PVY)-infected Nicotiana benthamiana plants two weeks post inoculation but not after six weeks. RNA-seq analysis revealed that transcripts related to plant defense and amino acid biosynthesis are upregulated in response to PVY infection and down regulated in response to aphid herbivory, and these patterns changed over time. Based on this analysis we identified a sesquiterpene synthase gene, terpene synthase 1 ( NbTPS1 ), that is upregulated early in PVY infection, but not later in infection. Using virus-induced gene silencing and transient overexpression in N. benthamiana , we demonstrate that PVY induction of NbTPS1 is required for increased aphid attraction to PVY-infected plants in the early stages of infection. These findings reveal that PVY temporally modulates transcriptional pathways associated with plant defense responses and volatile organic compounds that influence the behavior of aphid vectors.

  PublisherDOI

• Turnip mosaic virus infection cleaves MEDIATOR SUBUNIT16 in plants increasing plant susceptibility to the virus and its aphid vector Myzus persicae

  BMC Plant Biology · 2025-04-02 · 3 citations

  articleOpen accessSenior author

  Plant viruses both trigger and inhibit host plant defense responses, including defenses that target their insect vectors, such as aphids. Turnip mosaic viru (TuMV) infection and its protein, NIa-Pro (nuclear inclusion protease a), suppress aphid-induced plant defenses, however the mechanisms of this suppression are still largely unknown. In this study, we determined that NIa-Pro's protease activity is required to increase aphid performance on host plants and that 40 transcripts with predicted NIa-Pro cleavage sequences are regulated in Arabidopsis plants challenged with aphids and/or virus compared to healthy controls. One of the candidates, MEDIATOR 16 (MED16), regulates the transcription of ethylene (ET)/jasmonic acid (JA)-dependent defense responses against necrotrophic pathogens. We show that a nuclear localization signal is removed from MED16 by specific proteolytic cleavage in virus-infected plants and in plants overexpressing NIa-Pro in the presence of aphids. Although some cleavage was occasionally detected in the absence of virus infection, it occurred at a much higher rate in plants that were virus-infected or overexpressing NIa-Pro, especially when aphids were also present. This suggests MED16 functions in the nucleus may be impacted in virus infected plants. Consistent with this, induction of the MED16-dependent transcript of PLANT DEFENSIN 1.2 (PDF1.2), was reduced in virus-infected plants and in plants expressing NIa-Pro compared to controls, but not in plants expressing NIa-Pro C151A that lacks its protease activity. Finally, we show the performance of both the virus and the aphid vector was enhanced on med16 mutant Arabidopsis compared to controls. Overall, this study demonstrates MED16 regulates defense responses against both the virus and the aphid and provides insights into the mechanism by which TuMV suppresses anti-virus and anti-herbivore defenses.

  PublisherOA PDFDOI

• Insight on evolution of virus-encoded RNA silencing suppressor proteins from different viral families with an emphasis on viruses that infect Solanaceae crops

  2025-03-25

  preprintOpen access

  Viral suppressors of RNA silencing (VSRs) are proteins that interfere with antiviral defense mechanisms and enhance infection. For plant viruses, VSRs can be encoded in viral genomes and satellite molecules and play an important role in the virus life cycle and in overcoming host defenses. However, a comprehensive review on multifunctionality of VSRs and their role in the spread of plant diseases worldwide has not been performed. Here, we aim to synthesize the current understanding of the role of VSRs in the pathogenesis of Solanaceous plants, a family that includes many crop and medicinal plants. We focus on three key areas: (1) the diversity of VSRs and the mechanisms used to suppress anti-viral defense, (2) the role of VSRs in viral pathogenesis beyond interfering with host RNA-silencing, and (3) the co-evolution between VSRs and plant host proteins. Additionally, we describe how VSRs promote the development of diseases by altering various steps in the process of viral pathogenicity by inducing counter-defense mechanisms. Specifically, a substantial body of evidence suggests that VSRs induce suppression of antiviral silencing, abrogation of phytohormone signaling, and R-gene-mediated host defense. Furthermore, we discuss how identifying and characterizing novel interactions between VSRs and Solanaceous host factors may be leveraged for developing sustainable pathogen and pest management strategies.

  PublisherOA PDFDOI

• Motivating organic farmers to adopt practices that support the pest-suppressive microbiome relies on understanding their beliefs

  Renewable Agriculture and Food Systems · 2024-01-01 · 3 citations

  articleOpen accessSenior author

  Abstract Certified organic farming is a suite of regulated practices that can support social, economic, and ecological sustainability in agriculture. Despite the standardization and regulation of certifying bodies, practices adopted by organic farmers vary with potential heterogeneous effects on environmental outcomes. While it is accepted that beliefs can enable or constrain the adoption of farming practices, it remains unclear if variation in organic farmer beliefs mediates observed heterogeneity in practices and the ecology of farms. Communities of soil microorganisms that induce plant resistance and regulate insect herbivores offer a lens to explore the relationship between beliefs and practice adoption. Variation in insect herbivores across organic farms is common but none have studied the role of farmer beliefs in regulating pests through the soil microbiome. Herein, we hypothesized that variation in adoption of microbiome-supportive practices by organic farmers is driven by heterogeneity in their microbiome beliefs. We also investigate the importance of demographic variables and farm characteristics, compared to farmer beliefs, for adoption of practices that support the microbiome. To test our hypothesis, we surveyed the microbiome beliefs, farming practices, and motivations of 85 organic farmers in New York State, USA. We used affinity propagation to cluster farmers by their beliefs, and statistical models to evaluate variation in farming practice adoption and farmer motivations. Our survey received a 30.5% response rate, most organic farmers (≈96%) believed the soil microbiome was important for supporting plant defenses and reducing pests, and &lt;16% believed their farming practices were unimportant for promoting beneficial microbiomes. Seven clusters of farmers were identified that varied in their microbiome beliefs. Among the clusters ≈42% of farmers believed on-farm management and external factors (e.g., climate change) were important for promoting the microbiome. These farmers used fewer pesticides and synthetic mulches, more pre-planting practices (e.g., solarization), and were more motivated to adopt new practices to support the microbiome than their peers. The most important factors motivating adoption were reductions in pests, increased yields, and biodiversity benefits. Beliefs, demographics, and farm characteristics (e.g., time in organic management) were correlated with similar suites of farming practices, but only beliefs predicted farmer motivations. Our study suggests beliefs are key to understanding farmer motivations and promoting organic farming system sustainability via the pest-suppressive microbiome. More broadly, we suggest the need for socio-ecological approaches that account for farmer beliefs when studying the adoption of conservation practices in agroecosystems.

  PublisherOA PDFDOI

• Transcriptomic analysis reveals vector attraction to potato virus Y is mediated through temporal regulation of <i>TERPENE SYNTHASE 1</i> ( <i>TPS1</i> )

  bioRxiv (Cold Spring Harbor Laboratory) · 2024-12-29

  preprintOpen accessSenior authorCorresponding

  Abstract Virus-plant dynamics change over time, influencing interactions between plants and insect vectors. However, the signaling pathways and regulators that control these temporal responses remain largely unknown. In this study, we used insect performance and preference bioassays, RNA-Seq, and genetic tools to identify underlying mechanisms mediating temporal variation in plant-virus-vector interactions. We show that settlement and fecundity of the aphid vector, Myzus persicae , is increased on potato virus Y (PVY)-infected Nicotiana benthamiana plants two weeks after inoculation but not after six weeks. RNA-Seg analysis revealed transcripts related to plant defense and amino acid biosynthesis are upregulated in response to PVY infection and down regulated in response to aphid herbivory, and these patterns changed over time. Based on this analysis we identified a sesquiterpene synthase gene, terpene synthase 1 ( NbTPS1 ), that is upregulated early in PVY infection, but not at later infection time points. Using virus-induced gene silencing and transient overexpression in N. benthamiana we demonstrate that PVY induction of NbTPS1 is required for increased aphid attraction to PVY-infected plants in the early stages of infection. Taken together, PVY temporally regulates transcriptional pathways related to plant defense responses and volatile organic compounds that influence aphid vector performance and preference.

  PublisherOA PDFDOI

• Comprehensive Transcriptomic analysis reveals turnip mosaic virus infection and its aphid vector Myzus persicae cause large changes in gene regulatory networks and co- transcription of alternative spliced mRNAs in Arabidopsis thaliana

  Research Square · 2024-11-21

  preprintOpen access
  PublisherOA PDFDOI

Recent grants

• ECA-PGR: Transcriptional Regulation and Gene Networks Underlying Viral Recognition of Insect Vectors in Host Plants

  NSF · $1.2M · 2018–2020

Frequent coauthors

• Sayanta Bera

  University of Maryland, College Park

  32 shared

• Georg Jander

  Ithaca College

  27 shared

• Chad T. Nihranz

  Plant (United States)

  22 shared

• Seung Ho Chung

  Bennett Aerospace (United States)

  22 shared

• David W. Crowder

  Washington State University

  21 shared

• Tania Y. Toruño

  University of California, Davis

  18 shared

• Aurélie Bak

  University of California, Davis

  17 shared

• Saumik Basu

  17 shared

Labs

• CALS Research LabPI

Awards & honors

• 2023 Mid-Career Award Plant Genome Research Program (MCA-PGR…
• 2018 Early Career Award Plant Genome Research Program (ECA-P…
• 2017 ASPB Women’s Young Investigator Travel Award
• 2016 Neish Young Investigator Award of the Phytochemical Soc…
• 2014 MPMI Young Investigator Travel Grant