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Moroz N, Tanaka K. FlgII-28 Is a Major Flagellin-Derived Defense Elicitor in Potato. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2020; 33:247-255. [PMID: 31644369 DOI: 10.1094/mpmi-06-19-0164-r] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The first layer of plant immunity is deployed by recognition of pathogen-associated molecule patterns (PAMPs) and induction of early stress responses. Flagellin is the major protein component of the flagellum. Flagellin-derived peptide fragments such as Flg22, a short active peptide derived from the highly conserved part of the N-terminal region, are recognized as PAMPs by a specific perception system present in most higher plants. Some bacteria evade the plant recognition system by altering the Flg22 region in the flagellin. Instead, a small subset of plants (i.e., solanaceous plants) can sense these bacteria by recognizing a second region, termed FlgII-28. The function of FlgII-28 has been well-documented in tomato but not in potato plants. Here, we investigated the effect of FlgII-28 on several defense responses in potato. Cytosolic calcium (Ca2+) elevation is an early defense response upon pathogenic infection. We generated transgenic potato plants expressing aequorin, a nontoxic Ca2+-activated photoprotein. The results showed that FlgII-28 induced strong cytosolic Ca2+ elevation in a dose-dependent manner, whereas the response was attenuated when a Ca2+ channel blocker was added. In addition, the FlgII-28-triggered cytosolic Ca2+ elevation was shown to subsequently promote extracellular alkalinization, reactive oxygen species production, mitogen-activated protein kinase phosphorylation, and transcriptional reprogramming of defense-related genes in potato. Interestingly, all tested defense responses caused by FlgII-28 were significantly stronger than those caused by Flg22, suggesting that FlgII-28 acts as a primary flagellar PAMP to elicit multiple defense responses in potato.
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Affiliation(s)
- Natalia Moroz
- Department of Plant Pathology, Washington State University, Pullman, WA 99164-6430, U.S.A
| | - Kiwamu Tanaka
- Department of Plant Pathology, Washington State University, Pullman, WA 99164-6430, U.S.A
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Doblas-Ibáñez P, Deng K, Vasquez MF, Giese L, Cobine PA, Kolkman JM, King H, Jamann TM, Balint-Kurti P, De La Fuente L, Nelson RJ, Mackey D, Smith LG. Dominant, Heritable Resistance to Stewart's Wilt in Maize Is Associated with an Enhanced Vascular Defense Response to Infection with Pantoea stewartii. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2019; 32:1581-1597. [PMID: 31657672 DOI: 10.1094/mpmi-05-19-0129-r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Vascular wilt bacteria such as Pantoea stewartii, the causal agent of Stewart's bacterial wilt of maize (SW), are destructive pathogens that are difficult to control. These bacteria colonize the xylem, where they form biofilms that block sap flow leading to characteristic wilting symptoms. Heritable forms of SW resistance exist and are used in maize breeding programs but the underlying genes and mechanisms are mostly unknown. Here, we show that seedlings of maize inbred lines with pan1 mutations are highly resistant to SW. However, current evidence suggests that other genes introgressed along with pan1 are responsible for resistance. Genomic analyses of pan1 lines were used to identify candidate resistance genes. In-depth comparison of P. stewartii interaction with susceptible and resistant maize lines revealed an enhanced vascular defense response in pan1 lines characterized by accumulation of electron-dense materials in xylem conduits visible by electron microscopy. We propose that this vascular defense response restricts P. stewartii spread through the vasculature, reducing both systemic bacterial colonization of the xylem network and consequent wilting. Though apparently unrelated to the resistance phenotype of pan1 lines, we also demonstrate that the effector WtsE is essential for P. stewartii xylem dissemination, show evidence for a nutritional immunity response to P. stewartii that alters xylem sap composition, and present the first analysis of maize transcriptional responses to P. stewartii infection.
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Affiliation(s)
- Paula Doblas-Ibáñez
- Section of Cell and Developmental Biology, University of California at San Diego, La Jolla, CA 92093, U.S.A
| | - Kaiyue Deng
- Section of Cell and Developmental Biology, University of California at San Diego, La Jolla, CA 92093, U.S.A
| | - Miguel F Vasquez
- Section of Cell and Developmental Biology, University of California at San Diego, La Jolla, CA 92093, U.S.A
| | - Laura Giese
- Department of Horticulture and Crop Sciences, The Ohio State University, Columbus, OH 43210, U.S.A
| | - Paul A Cobine
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, U.S.A
| | - Judith M Kolkman
- School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, U.S.A
| | - Helen King
- Section of Cell and Developmental Biology, University of California at San Diego, La Jolla, CA 92093, U.S.A
| | - Tiffany M Jamann
- Department of Crop Sciences, University of Illinois Urbana-Champaign, Urbana, IL 61801, U.S.A
| | - Peter Balint-Kurti
- United States Department of Agriculture-Agricultural Research Service, Plant Science Research Unit, Raleigh, NC 27695, U.S.A. and Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC 27695, U.S.A
| | | | - Rebecca J Nelson
- School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, U.S.A
| | - David Mackey
- Department of Horticulture and Crop Sciences, The Ohio State University, Columbus, OH 43210, U.S.A
| | - Laurie G Smith
- Section of Cell and Developmental Biology, University of California at San Diego, La Jolla, CA 92093, U.S.A
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Mensi I, Vernerey MS, Gargani D, Nicole M, Rott P. Breaking dogmas: the plant vascular pathogen Xanthomonas albilineans is able to invade non-vascular tissues despite its reduced genome. Open Biol 2014; 4:130116. [PMID: 24522883 PMCID: PMC3938051 DOI: 10.1098/rsob.130116] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 01/20/2014] [Indexed: 12/13/2022] Open
Abstract
Xanthomonas albilineans, the causal agent of sugarcane leaf scald, is missing the Hrp type III secretion system that is used by many Gram-negative bacteria to colonize their host. Until now, this pathogen was considered as strictly limited to the xylem of sugarcane. We used confocal laser scanning microscopy, immunocytochemistry and transmission electron microscopy (TEM) to investigate the localization of X. albilineans in diseased sugarcane. Sugarcane plants were inoculated with strains of the pathogen labelled with a green fluorescent protein. Confocal microscopy observations of symptomatic leaves confirmed the presence of the pathogen in the protoxylem and metaxylem; however, X. albilineans was also observed in phloem, parenchyma and bulliform cells of the infected leaves. Similarly, vascular bundles of infected sugarcane stalks were invaded by X. albilineans. Surprisingly, the pathogen was also observed in apparently intact storage cells of the stalk and in intercellular spaces between these cells. Most of these observations made by confocal microscopy were confirmed by TEM. The pathogen exits the xylem following cell wall and middle lamellae degradation, thus creating openings to reach parenchyma cells. This is the first description of a plant pathogenic vascular bacterium invading apparently intact non-vascular plant tissues and multiplying in parenchyma cells.
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Affiliation(s)
- Imène Mensi
- CIRAD, UMR BGPI, TA A-54/K, Montpellier Cedex 5 34398, France
| | | | - Daniel Gargani
- CIRAD, UMR BGPI, TA A-54/K, Montpellier Cedex 5 34398, France
| | - Michel Nicole
- IRD, UMR RPB, BP 64501, Montpellier Cedex 5 34394, France
| | - Philippe Rott
- CIRAD, UMR BGPI, TA A-54/K, Montpellier Cedex 5 34398, France
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