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Two chloroplast-localized proteins: AtNHR2A and AtNHR2B, contribute to callose deposition during nonhost disease resistance in Arabidopsis

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Title Two chloroplast-localized proteins: AtNHR2A and AtNHR2B, contribute to callose deposition during nonhost disease resistance in Arabidopsis
 
Creator Singh, Raksha
Lee, Seonghee
Ortega, Laura
Ramu, Vemanna S.
Senthil-Kumar, Muthappa
Blancaflor, Elison B.
Rojas, Clemencia M.
Mysore, Kirankumar S.
 
Subject Arabidopsis
AtNHR2A and AtNHR2B
chloroplast-localized proteins
 
Description Accepted date: 6 June 2018
Plants are naturally resistant to most pathogens through a broad and durable defense response called nonhost disease resistance. Nonhost disease resistance is a complex process that includes preformed physical and chemical barriers and induced responses. In spite of its importance, many components of nonhost disease resistance remain to be identified and characterized. Using virus-induced gene silencing in Nicotiana benthamiana, we discovered a novel gene that we named NbNHR2 (N. benthamiana nonhost resistance 2). NbNHR2-silenced plants were susceptible to the non-adapted pathogen Pseudomonas syringae pv. tomato T1 that does not cause disease in wild-type or non-silenced N. benthamiana plants. We found two orthologous genes in Arabidopsis thaliana: AtNHR2A and AtNHR2B. Similar to the results obtained in N. benthamiana, Atnhr2a and Atnhr2b mutants were susceptible to the non-adapted bacterial pathogen of A. thaliana, P. syringae pv. tabaci. We further found that these mutants were also defective in callose deposition. AtNHR2A and AtNHR2B fluorescent protein fusions transiently expressed in N. benthamiana localized predominantly to chloroplasts and a few unidentified dynamic puncta. RFP-AtNHR2A and AtNHR2B-GFP displayed overlapping signals in chloroplasts indicating that the two proteins could interact; a notion supported by co-immunoprecipitation studies. We propose that AtNHR2A and AtNHR2B are new components of a chloroplast-signaling pathway that activates callose deposition to the cell wall in response to bacterial pathogens.
We thank Scott Winter and Maria Angélica Parra-Galindo for assistance with statistical analysis and Janie Gallaway for plant care. We also thank Dr. Ioannis Tzanetakis for helpful advice regarding the phylogenetic analysis, Dr. Ramegowda Venkategowda for critical reading of the manuscript and all members of the Rojas lab for productive discussions. This work was supported by Noble Research Institute, LLC.(KSM) and by the start-up support from the University of Arkansas (CMR).
 
Date 2018-06-13T10:24:14Z
2018-06-13T10:24:14Z
2018
 
Type Article
 
Identifier Molecular Plant-Microbe Interactions, 31(12): 1280-1290
1943-7706
http://223.31.159.10:8080/jspui/handle/123456789/860
https://apsjournals.apsnet.org/doi/10.1094/MPMI-04-18-0094-R
https://doi.org/10.1094/MPMI-04-18-0094-R
 
Language en_US
 
Format application/pdf
 
Publisher American Phytopathological Society