Research & Projects

An in-depth look at Solanaceae recognition and response to bacterial-derived MAMPs.

Plants must recognize and respond to microbes. There are two main models that describe these interactions: effector-triggered immunity (ETI) and pattern-triggered immunity (PTI). In PTI, plants use pattern recognition receptors (PRRs) to recognize specific pathogen molecular structures. Often, these are protein sequences such as those in bacterial flagellin or chitin, and are known as Pathogen-Associated Molecular Patterns (PAMPs) or Microbe-Associated Molecular Patterns (MAMPs)

Subsequent induction of PTI results in an increase of cellular responses aimed at preventing further pathogen attack. Integral components of the PTI response are known to include seedling growth inhibition, mitogen-activated protein kinases (MAPKs), callose deposition, the production of reactive oxygen species (ROS), lignification, and calcium influxes.

In Arabidopsis, all of these responses are present in response to flg22 and elf18, but tomato species exhibit additional PRRs not found in Arabidopsis species. The focus of my dissertation is to look at the responses of tomato roots using various PAMP/PRR combinations, including that of both foliar and soil-borne bacterial pathogens.

Dissertation Objectives

Categorizing the pattern triggered immunity responses of tomato roots to various bacteria-derived peptides; elucidating how intracellular signaling cascades of bacteria-derived peptides in tomato roots elicit distinct pattern-triggered immune responses.
Investigating development-specific responses of tomato roots to various bacterial-derived peptides, including immediate and long-term defense regulation.
Understanding how exopolysaccharides of Ralstonia solanacearum function as virulence factor at the face of the Tomato-Ralstonia pathosystem.

Research Publications

Leuschen-Kohl R, Roberts R, Stevens D, Zhang N, Pilkey B, Buchanan S, Coaker G, and Iyer-Pascuzzi A. (2025). Tomato Roots Exhibit Development-Specific Responses to Bacterial-Derived Peptides. Plant, Cell, & Environment. https://doi.org/10.1111/pce.70164

Murff M, Leuschen-Kohl R, Pilkey B, and Iyer-Pascuzzi A. (2025). Below-ground tissues of Capsicum annuum respond to conserved bacterial peptides with pattern-triggered immunity. microPublication Biology. https://doi.org/10.17912/micropub.biology.001726

Rivera-Zuluaga K, Choudhary P, Mohammad S, Leuschen-Kohl R, Trejos-Ramirez S, Pascuzzi P, and Iyer-Pascuzzi A. (2024). Pleiotropic phenotypes of a tomato auxin pathway mutant enable resistance to multiple species of Ralstonia. MPMI. https://apsjournals.apsnet.org/doi/10.1094/MPMI-10-24-0123-R

Meline V, Hendrich CG, Truchon AN, Caldwell D, Hiles R, Leuschen-Kohl R, Tran T, Mitra RM, Allen C, and Iyer-Pascuzzi A. (2022) Tomato deploys defense and growth simultaneously to resist bacterial wilt disease. Plant, Cell, & Environment. doi: 10.1111/pce.14456.

Leuschen RL* and Downing BL* (2020) Gene Editing of Arabidopsis thaliana RNA Dependent RNA Polymerases Using CRISPR/Cas9. The FASEB Journal, 34: 1-1.

Ghimire G, Moore MM, Leuschen R, Nagasaka S, Kameta N, Masuda M, Higgins DA, and Ito T. (2020) Influences of hydrogen bonding-based stabilization of bolaamphiphile layers on molecular diffusion within organic nanotubes having inner carboxyl groups. Langmuir, 36(22). doi: 10.1021/acs.langmuir.0c00556.

In Review

Leuschen-Kohl R.*, Pilkey B*, Baruah R, Buchanan S, Joshy S, Lindemann S, and Iyer-Pascuzzi A. [in prep] Ralstonia EPS serves a dual role as an antioxidant and immune elicitor in tomato.

Leuschen-Kohl R and Iyer-Pascuzzi A. [in prep] Current understanding of pattern-recognition receptors and extracellular immunity in the Solanaceae.

Research Presentations

Invited Talks *presenting author

Leuschen-Kohl, R.* “From Roots to Research: An Indigenous Woman’s Path in Plant Biology”, Session: Fostering Inclusion in Plant Biology, American Society for Plant Biology 2025 Extended Virtual Session, August 2025.

Leuschen-Kohl, R.* and Iyer-Pascuzzi, A. “Plant resilience through pattern-recognition receptors in Solanaceae.” Montana University System Sloan Indigenous Graduate Partnership Retreat, Butte, MT, April 2025.

Leuschen-Kohl, R.* Roberts, R., Stevens, D., Buchanan, S., Pilkey, B., Coaker, G., and Iyer-Pascuzzi, A. “At the Interface of Invasion: Deciphering the Tomato Root Response to Flagellin-Derived Peptides.” Botany and Plant Pathology Department Showcase, Purdue University, West Lafayette, IN, November 2024.

Leuschen-Kohl, R.* Roberts, R., Stevens, D., Buchanan, S., Pilkey, B., Coaker, G., and Iyer-Pascuzzi, A. “At the Interface of Invasion: Deciphering the Tomato Root Response to Flagellin-Derived Peptides.” Center for Plant Biology Symposium, Purdue University, West Lafayette, IN, September 2024.

Leuschen-Kohl, R.* and Brandon, T. “Preparing and Presenting Research Posters for an Undergraduate Audience.” SCARF, Purdue University, West Lafayette, IN. June 2024.

Leuschen-Kohl, R.* and Iyer-Pascuzzi, A. “Uncovering initial defense responses to bacterial invasion in tomato root systems.” Alfred P. Sloan Foundation visit to University of Kansas and Haskell Indian Nations University, Lawrence, KS, April 2024.

Leuschen, R.L.* and Downing, B.L.* “Mutational inactivation of Arabidopsis thaliana RNA polymerases by gene editing” Undergraduate Creative Activities and Research Experience – RED Talk, Lincoln, NE, Fall 2019. (Invited talk)

Research Talks *presenting author

Leuschen-Kohl, R.*, Buchanan, S. and Iyer-Pascuzzi, A. “Uncovering initial defense responses to bacterial invasion in tomato root systems.” Alfred P. Sloan Foundation visit to University of Kansas and Haskell Indian Nations University, Lawrence, KS, April 2024.

Leuschen-Kohl, R.* and Iyer-Pascuzzi, A. “Peptide-driven immune responses defy the growth-defense tradeoff in tomato.” Department of Botany and Plant Pathology Annual Showcase, West Lafayette, IN, November 2023.

Leuschen-Kohl, R.* and Iyer-Pascuzzi, A. “Whole-Root and Developmental Zone Characterization of Pattern-Triggered Immunity in Tomato.” Ralstonia Rooters Annual Meeting, West Lafayette, IN, December 2021.

Leuschen, R.L.*, Ghimire, G., and Higgins, D.A. “Diffusion Study of Rhodamine B in Carboxyl Terminated Nanotubes.” Summer 2018 REU Symposium, Kansas State University, Manhattan, KS, August 2018.

Poster Presentations *presenting author

Leuschen-Kohl, R.*, Buchanan, S., and Iyer-Pascuzzi, A. “Transcriptomic analysis of tomato root reveals developing regions are primary location of pattern triggered immunity response to bacterial-derived peptide.” Plant Health 2024, Memphis, TN, July 2024.

Leuschen-Kohl, R.*, Roberts, R., Buchanan, S., and Iyer-Pascuzzi, A. “Intracellular Signaling Cascades of Bacterial-Derived Peptides in Tomato Roots Elicit Distinct Pattern-Triggered Immune Responses.” Botany and Plant Pathology Departmental Showcase, Purdue University, West Lafayette, IN, Oct 2023.

Leuschen-Kohl, R.* and Iyer-Pascuzzi, A. “Tomato Root Response to Pathogen Associated Molecular Patterns (PAMPs): Challenging the common PTI response.” Center for Plant Biology Plant Science Symposium, Purdue University, College of Agriculture, West Lafayette, IN, September 2023.

Leuschen-Kohl, R.* and Iyer-Pascuzzi, A. “Tomato Root Response to Pathogen Associated Molecular Patterns (PAMPs): Challenging the common PTI response.” Plant Health - American Phytopathological Society Annual Meeting, Denver, CO, August 2023.

Leuschen-Kohl, R.* and Iyer-Pascuzzi, A. “Tomato Root Response to Pathogen Associated Molecular Patterns (PAMPs): Challenging the common PTI response.” International Society for Molecular Plant Microbe Interactions 2023 Congress, Providence, RI, July 2023.

Leuschen-Kohl, R.* and Iyer-Pascuzzi, A. “Characterization of Root PTI Response Among Tomato Cultivars.” Botany and Plant Pathology Departmental Showcase, Beck Agricultural Center, West Lafayette, IN, December 2022.

Leuschen-Kohl, R.* and Iyer-Pascuzzi, A. “Characterization of Root PTI Response Among Tomato Cultivars.” Graduate Student Welcoming and Networking Event, Purdue University College of Agriculture, West Lafayette, IN, September 2022.

Leuschen, R.* and Iyer-Pascuzzi, A. “Characterization of Root PTI Response Among Tomato Cultivars.” Center for Plant Biology Spring Retreat, Beck Agricultural Center, West Lafayette, IN, May 2022.

Leuschen, R.* and Downing, B.L. “Mutational inactivation of Arabidopsis thaliana RNA polymerases by gene editing” 2020 National Meeting of the American Society for Biochemistry and Molecular Biology, virtual, May 2020.

Leuschen, R.* and Downing, B.L. “Mutational inactivation of Arabidopsis thaliana RNA polymerases by gene editing” Nebraska Center for Virology 2019 Symposium, Lincoln, NE, September 2019.

Leuschen, R.* and Downing, B.L.* “Mutational inactivation of Arabidopsis thaliana RNA polymerases by gene editing” Summer Undergraduate Research Symposium, Lincoln, NE, August 2019.

Leuschen, R.L.*, Ghimire, G., and Higgins, D.A. “Diffusion Study of Rhodamine B in Carboxyl Terminated Nanotubes.” 2018 Summer Undergraduate Research Fair, University of Nebraska, Lincoln, NE, August 2018.

Leuschen, R.L.*, Ghimire, G., and Higgins, D.A. “Diffusion Study of Rhodamine B in Carboxyl Terminated Nanotubes.” Summer 2018 REU Symposium, Kansas State University, Manhattan, KS, August 2018.

Mentored Presentations *presenting author

Joshy, S.*, Pilkey, B., Leuschen-Kohl, R., Buchanan, S., Baruah, R., Lindemann, S., and Iyer-Pascuzzi, A. "Title" Summer Undergraduate Research Symposium, Purdue University, West Lafayette, IN, July 2024.

Pilkey, B.*, Joshy, S., Leuschen-Kohl, R., Buchanan, S., Baruah, R., Lindemann, S., and Iyer-Pascuzzi, A. "Title" Summer Undergraduate Research Symposium, Purdue University, West Lafayette, IN, July 2024.

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