Skip to main page content (VSports)
U.S. flag

An official website of the United States government

Dot gov

The . gov means it’s official VSports app下载. Federal government websites often end in . gov or . mil. Before sharing sensitive information, make sure you’re on a federal government site. .

Https

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely V体育官网. .

. 2009 Oct;151(2):820-9.
doi: 10.1104/pp.109.142067. Epub 2009 Aug 21.

Extracellular DNA is required for root tip resistance to fungal infection

Fushi Wen  1 , Gerard J White, Hans D VanEtten, Zhongguo Xiong, Martha C Hawes
Affiliations

V体育ios版 - Extracellular DNA is required for root tip resistance to fungal infection

Fushi Wen (VSports) et al. Plant Physiol. 2009 Oct.

Abstract

Plant defense involves a complex array of biochemical interactions, many of which occur in the extracellular environment. The apical 1- to 2-mm root tip housing apical and root cap meristems is resistant to infection by most pathogens, so growth and gravity sensing often proceed normally even when other sites on the root are invaded VSports手机版. The mechanism of this resistance is unknown but appears to involve a mucilaginous matrix or "slime" composed of proteins, polysaccharides, and detached living cells called "border cells. " Here, we report that extracellular DNA (exDNA) is a component of root cap slime and that exDNA degradation during inoculation by a fungal pathogen results in loss of root tip resistance to infection. Most root tips (>95%) escape infection even when immersed in inoculum from the root-rotting pathogen Nectria haematococca. By contrast, 100% of inoculated root tips treated with DNase I developed necrosis. Treatment with BAL31, an exonuclease that digests DNA more slowly than DNase I, also resulted in increased root tip infection, but the onset of infection was delayed. Control root tips or fungal spores treated with nuclease alone exhibited normal morphology and growth. Pea (Pisum sativum) root tips incubated with [(32)P]dCTP during a 1-h period when no cell death occurs yielded root cap slime containing (32)P-labeled exDNA. Our results suggest that exDNA is a previously unrecognized component of plant defense, an observation that is in accordance with the recent discovery that exDNA from white blood cells plays a key role in the vertebrate immune response against microbial pathogens. .

PubMed Disclaimer

Figures

Figure 1.
Figure 1.
Light microscopic visualization of the fibrillar nature of root cap slime. A, Staining of cell-free material with DAPI reveals strands of DAPI-positive material. B, Similar structures were visible in response to staining with SYTOX green (Jones and Singer, 2001). Bars = 0.1 mm.
Figure 2.
Figure 2.
Loss of root tip resistance to infection in pea roots treated with DNase I at the time of inoculation with N. haematococca (N. h.). A, Most inoculated root tips resist infection, as described (Gunawardena and Hawes, 2002; Gunawardena et al., 2005; Wen et al., 2007): no lesions form at the root tip, which remains white and continues to grow in a manner indistinguishable from that of uninoculated controls. B, When coinoculated with DNase I (1.2 units) and fungal spores, 100% of inoculated root tips developed necrosis within 48 to 72 h. Root growth ceased, and fungal growth proliferated (arrowheads). C, Control roots treated with DNase I alone did not develop necrosis, and there was no significant difference in mean growth of control roots, with or without DNase I treatment.
Figure 3.
Figure 3.
Early changes in N. haematococca (green)-root tip (red) interactions in response to DNase I treatment using a GFP reporter strain and viewed by confocal laser scanning microscopy. A, Limited growth of fungal hyphae (double white arrow) is evident at a distance from root tips (red). Detached border cells (red) are indicated with the white arrow. B, In DNase I-treated roots, proliferating fungal hyphae (double white arrow) can be seen among border cells (white arrow) and penetrating the root tip epidermis (black arrows). Photographs were taken at 36 h after inoculation, before visible necrosis had developed. GFP green fungal hyphae and red root autofluorescence images were obtained by dual excitation at 490 and 568 nm, respectively. Bar = 20 μm.
Figure 4.
Figure 4.
Delayed degradation of DNA by the exonuclease BAL31 compared with DNase I. Electrophoresis of pea genomic DNA treated with BAL31 (B) or DNase I (D), respectively, for 2, 24, or 72 h.
Figure 5.
Figure 5.
Delayed onset of symptoms in inoculated root tips treated with BAL31 compared with DNase I. A, Root tips 72 h after inoculation with N. haematococca (N. h.) are free of necrosis despite being surrounded by hyphal growth on surrounding border cells, as described (Gunawardena and Hawes, 2002; Gunawardena et al., 2005; Wen et al. 2007). B, Root tips 72 h after inoculation with N. haematococca in the presence of BAL31 exhibit tan discoloration at the root tips, but roots continue to grow. C, Root tips 72 h after inoculation with N. haematococca in the presence of DNase I exhibit dark brown to blackened necrosis. Root tips were treated with 1.2 units of BAL31 or DNase I.
Figure 6.
Figure 6.
exDNA in root cap slime. A, exDNA isolated from root cap slime (lane 1) and after digestion by treatment with DNase I (lane 2). B, Autoradiograph of exDNA collected from root tips fed with [32P]dCTP for 1 h (lane 1) and cell-free root mucilage collected, mixed with [32P]dCTP for 1 h, and subjected to electrophoresis (lane 2).
See this image and copyright information in PMC

References

    1. Allesen-Holm M, Barken KB, Yang L, Klausen M, Webb JS, Kjelleberg S, Molin S, Givskov M, Tolker-Nielsen T (2006) A characterization of the DNA release in Pseudomonas aeruginosa cultures and biofilms. Mol Microbiol 59: 1114–1128 - PubMed
    1. Balestrazzi A, Bonadei M, Carbonepa D (2007) Nuclease-producing bacteria in soil cultivated with herbicide resistant transgenic white poplars. Ann Microbiol 57: 531–536
    1. Barlow PW (2003) The root cap: cell dynamics, cell differentiation and cap function. J Plant Growth Regul 21: 261–286
    1. Braun W, Whallon J (1954) The effects of DNA and enzyme-treated DNA on bacterial population changes. Proc Natl Acad Sci USA 40: 162–164 - PMC - PubMed
    1. Brigham LA, Woo HH, Hawes MC (1995) Differential expression of proteins and mRNAs from border cells and root tips of pea. Plant Physiol 109: 457–460 - PMC (VSports注册入口) - PubMed

V体育2025版 - Publication types

"VSports在线直播" MeSH terms