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Topic1_Plant cytoskeleton

作者:   发布时间:2014-11-18 00:43:33   浏览次数:370


Plant innate immunity is composed of two layers. Basal immunity is triggered by pathogen-associated molecular patterns (PAMPs) such as the flagellin-peptide flg22 and is termed PAMP-triggered immunity (PTI) (Jones & Dangl, 2006). In addition, effector-triggered immunity (ETI) linked with programmed cell death and cytoskeletal reorganization can be induced by pathogen-derived factors, such as the Harpin proteins originating from phytopathogenic bacteria. To get insight into the link between cytoskeleton and PTI or ETI, this study followed the responses of actin filaments and microtubules to flg22 and HrpZ in vivo by spinning-disc confocal microscopy in GFP-tagged marker lines of tobacco BY-2. At a concentration that clearly impairs mitosis, flg22 can induce only subtle cytoskeletal responses. In contrast, HrpZ causes a rapid and massive bundling of actin microfilaments (completed in ~20 min, i.e. almost simultaneously with extracellular alkalinization), which is followed by progressive disintegration of actin cables and cytoplasmic microtubules, a loss of cytoplasmic structure, and vacuolar disintegration. Cytoskeletal disruption is proposed as an early event that discriminates HrpZ-triggered ETI-like defence from flg22-triggered PTI.


Resistance to abiotic and biotic stress is a central topic for sustainable agriculture, especially in grapevine, one of the field crops with the highest economic output per acreage. As early cellular factors for plant defense, actin microfilaments (AF) are of high relevance. We therefore generated a transgenic actin marker line for grapevine by expressing a fusion protein between green fluorescent protein and the second actin-binding domain of Arabidopsis (Arabidopsis thaliana) fimbrin, AtFIM1. Based on this first cytoskeletal-marker line in grapevine, the response of AFs to phytopathogenic microorganisms could be followed in vivo. Upon inoculation with fluorescently labeled strains of phytopathogenic bacteria, actin responses were confined to the guard cells. In contrast, upon contact with zoospores of Plasmopara viticola, not only the guard cells, but also epidermal pavement cells, where no zoospores had attached responded with the formation of a perinuclear actin basket. Our data support the hypothesis that guard cells act as pacemakers of defense, dominating the responses of the remaining epidermal cells.


Plant microtubules (MTs), in addition to their role in cell division and cell expansion respond to various stress signals. To understand the biological function of this early response requires non-destructive strategies for visualisation in cellular models that are highly responsive to stress signals. We have therefore generated a transgenic tubulin marker line for a cell line from the grapevine Vitis rupestris which readily responds to stress factors of defence-related and abiotic stresses based on a fusion of the green fluorescent protein with Arabidopsis ß-tubulin 6. By a combination of spinning-disk confocal microscopy with quantitative image analysis we can detect early and specific responses of MTs to defence-related and abiotic stress factors in vivo. We observe that HrpZ, a bacterial elicitor that can trigger programmed cell death, rapidly eliminates radial MTs, followed by a slower depletion of the cortical array. Jasmonic acid, in contrast, induces bundling of cortical MTs. Auxin reduces the thickness of cortical MTs. This effect follows a characteristic bell-shaped dose-dependency and can revert jasmonic acid-induced bundling. Impeded cell expansion in consequence of stress treatment or superoptimal auxin is linked with the appearance of intranuclear tubulin speckles. The early and stimulus-specific responses of MTs are discussed with respect to a function in processing or decoding of stress signals.

Jones & Dangl, The plant immune system. 2006, Nature 444, 323-329


Xin Guan, Günther Buchholz, Peter Nick. 2014. Tubulin marker line of grapevine suspension cells as a tool to follow early stress responses. Journal of Plant Physiology. in press


Xin Guan, Günther Buchholz, Peter Nick. 2014. Actin marker lines in grapevine reveal a gatekeeper function of guard cells. Journal of Plant Physiology, 171: 1164-1173 


Xin Guan, Günther Buchholz, Peter Nick. 2013. The cytoskeleton is disrupted by the bacterial effector HrpZ, but not by the bacterial PAMP flg22 in tobacco BY-2 cells. Journal of Experimental Botany, 64: 1805-1816. 






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