Biotic Stress/Applied Plant Bio

Abstract

CS-18-4 - Unraveling the plant endomembrane pathway involved in callose deposition against bacterial pathogens and its interplay with bacterial effectors

Monday, July 16
4:18 PM - 4:38 PM

Plants are constantly exposed to a high diversity of pathogens present in the environment and defend themselves by a complex innate immune system to detect the threat of the pathogen and prevent its proliferation. One of the outputs of defense responses is the fortification of the cell wall through the deposition of callose (a ß-1,3-glucan polymer). In spite of its importance, it is still not fully understood how callose biosynthetic and regulatory pathways are integrated with the cellular processes that mediate its deposition to the cell wall in response to pathogen challenge. Using a fast-forward genetic screen based on virus-induced gene silencing (VIGS) in Nicotiana benthamiana, we identified a novel gene involved in plant immunity that we named nonhost resistant 2 (NHR2). NHR2 is broadly conserved in plants but its function has not been investigated. Arabidopsis thaliana has two NHR2 orthologs: AtNHR2A and AtNHR2B. Atnhr2a and Atnhr2b mutants are compromised in plant immunity and we further found that they are defective in deposition of callose in response to bacterial pathogens. Using live-cell imaging, we showed that fluorescent versions of AtNHR2A and AtNHR2B localize to the cytoplasm and to small and dynamic subcellular structures reminiscent of the endomembrane system. Genetic analysis showed that AtNHR2A and AtNHR2B showed that AtNHR2A and AtNHR2B are components of the PEN2 (Penetration 2)/PEN3 (penetration 3) pathway that operates at the plasma membrane/cell wall interface. Interestingly, AtNHR2A and AtNHR2B localization and stability are affected by the bacterial pathogen Pseudomomas syringae pv. tomato DC3000 through the activities of specific effectors acting redundantly. This work provides fundamental knowledge regarding the cellular mechanisms underlying callose deposition during plant defense responses and how virulent pathogens interfere with this process.


 

Co-Authors

Raksha Singh – University of Arkansas; Laura Ortega – University of Arkansas; Seonghee Lee – University of Florida; Senthil-Kumar Muthappa – National Institute of Plant Genome Research; Kiran Mysore – Noble Research Institute

Clemencia Rojas, PhD

Assistant Professor
University of Arkansas

Clemencia M. Rojas obtained her Bachelor's of Science degree in Microbiology at the Universidad de los Andes in from Bogota, Colombia and joined the International Center for Tropical Agriculture (CIAT) as research assistant to characterize the genetic diversity of Magnaporthe oryzae, the fungus causing the rice blast disease. This collaborative work led her to Purdue University where she obtained a Master's degree in Genetics. She continued investigating plant diseases, specifically the bacterial pathogen Dickeya dadantii, for her PhD dissertation at Cornell University. Her postdoctoral research included investigating mechanisms of pathogenicity in the human pathogen Salmonella typhimurium, at Washington University School of Medicine and, identifying and characterizing genes in plants involved in plant immunity at the Noble Research Institute. Currently, she is an Assistant Professor in the Department of Plant Pathology at the University of Arkansas, investigating the molecular and cellular interactions between plants and plant pathogenic bacteria.

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CS-18-4 - Unraveling the plant endomembrane pathway involved in callose deposition against bacterial pathogens and its interplay with bacterial effectors



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