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1.
The infectious structures for the development and differentiation of Erysiphe graminis DC. f. sp. tritici March., the pathogen of wheat powdery mildew, under the effects of exogenous zeatin was studied by methods of light and electron
scanning microscopy. It was shown for the first time that physiologically active substances, specifically phytohormones of
the cytokinin type, can affect dimensions of the halo revealed in the pathogen penetration site at cytochemical staining.
Treatment with zeatin affected conidia germination and pathogen growth in the ectophytic stage. The concentration curve of
the action of zeatin for the number of mature pathogen colonies (6 days after infection) was represented by a multiphase curve
with two maxima (1 and 3 μM) and one minimum (1.5 μM). Similar curves have been obtained for the number of normal appressoria
and for large halo diameters, which possibly indicates the existence of the factors affecting these both parameters, as well
as the final number of pathogen colonies. The obtained data indicate that the origin of the multiphase dose response curve
for effect of cytokinins on the development of powdery mildew pathogen is connected with factors that are active at the early
stages of pathogenesis. 相似文献
2.
Defense Reactions in Host and Nonhost Plants Against the Soybean Rust Fungus (Phakopsora pachyrhizi Syd.) 总被引:1,自引:0,他引:1
Growth and development of two races of the soybean rust fungus (Phakopsora pachyrhizi Syd.) were compared on host and nonhost plants. Both groups had several lines of defense, each of which could stop a part of attacking uredospores. Germ tubes and appressoria were produced equally well on hosts and nonhosts. A reduced formation of penetration hyphae contributed to the resistance of nonhosts and resistant host genotypes. In the epidermal cells of wheat and barley leaves, lower frequencies of penetration hyphae coincided with the production of papillae-like structures which were not penetrated. The last line of defense of all nonhosts was localized in the epidermal cell where the growth of the penetration hyphae was arrested definitively. The colony development in these species was suppressed completely. In highly resistant host genotypes the last defense reaction occurred later as a hypersensitive cell collapse which interrupted the growth of the rust colony. 相似文献
3.
Rice (Oryza sativa) cv. Nipponbare expresses non-host resistance (NHR) to the wheat leaf rust fungus, Puccinia triticina f. sp. tritici (Ptt). When the leaves of cv. Nipponbare were inoculated with Ptt, approx 93% of the urediniospores germinated on the leaf surface, but only 10% of the germinated spores formed appressoria
over the stomata at one day post inoculation (1 dpi). Hydrogen peroxide (H2O2) accumulated in host cells around the appressoria at 3 dpi. Approx. 3% of the appressoria produced short hyphae inside the
leaf, and fluorescence was observed in tissue invaded by the hyphae by 7 dpi. At 22 dpi, 0.2% of the sites with appressoria
formed branching infection hypha in mesophyll cells, but no substomatal vesicles, haustorial mother cells or haustoria were
observed. Proteins were extracted from leaves 3 dpi and analyzed by two-dimensional gel electrophoresis (2-DE). A total 33
spots were reproducibly up-regulated and 9 were down-regulated by infection compared to the water inoculated control. Of these,
30 were identified by MALDI-TOF Mass Spectrometry. The identified proteins participate in defense/stress responses, energy/carbohydrate
metabolism, oxidation–reduction processes, protein folding/turnover/cleavage/degradation, signal transduction and cell death
regulation. The results indicates that NHR of rice to Ptt is consistent with a shift in protein and energy metabolism, increased antimicrobial activities, possibly including phytoalexin
accumulation and cell wall reinforcement, increased cell repair, antioxidive and detoxification reactions, and enhanced prevention
of plant cell death. Nearly half of the up-regulated identified proteins were associated with chloroplast and mitochondrial
physiology suggesting important roles for these organelles during NHR. 相似文献
4.
Effects of soil water level on the development of adult plant resistance to powdery mildew in barley 总被引:4,自引:0,他引:4
Barley grown in dry soil developed greater adult plant resistance (APR) to powdery mildew (Erysiphe graminis DC. f. sp. hordei Mérat) than barley grown in wet soil. Conidial germination and appressorium formation were less, and fungal development between formation of appressoria and elongating secondary hyphae on upper leaves was inhibited, when adult plants were grown in dry soil. Mildew colonies expanded more slowly on leaves of adult plants than on leaves of seedlings, especially if adult plants had grown in dry soil. APR was reduced if plants, previously grown in dry soil, were well watered more than 32 h before inoculation. Conidia originating from plants grown in dry soil had a lower solute potential and greater ability to infect plants grown in dry but not wet soil than conidia originating from plants grown in wet soil. APR could not be attributed simply to increased cell wall or cuticle thickness, nor to lowered leaf solute potentials, as has sometimes been suggested for powdery mildew diseases. Increasing plant age and water stress induced increases in cell wall and cuticle thickness, but these changes did not always coincide with changes in disease resistance. Increasing plant age and water stress also lowered leaf solute potentials but fungal solute potentials were lower than leaf solute potentials and, more importantly, were lower than leaf water potentials. Thus, fungal growth was not limited by the availability of water from the host during penetration and hyphal establishment. It is suggested that resistance levels may be determined not by the thickness of epidermal structures, nor by lowering of solute potential per se, but by specific substances harmful to the fungus which accumulate in either cell wall, cuticle or sap, and whose concentration is dependent on the age and water stress of leaves. 相似文献
5.
Emma W. Gachomo Manfredo J. Seufferheld Simeon O. Kotchoni 《Molecular biology reports》2010,37(7):3583-3591
Previous studies have shown the role of melanized appressoria in the pathogenicity of various fungi. Diplocarpon rosae is a worldwide outdoor fungal pathogen of rose plants causing black spot disease of rose leaves. To fully understand how
this fungus colonizes its host, which is critical for the development of an efficient and sustainable disease management program,
we studied the fungal (especially the appressoria) structures of D. rosae in detail at an early stage of infection. Using both microscopic and biochemical analyses, we observed strong melanized appressoria
formation localized at the point of D. rosae penetration, which forms the pathogen–plant interface. Treatment of infected plants with melanin biosynthesis inhibitors
(MBIs) prevented melanization of D. rosae appressoria and positively correlated with significant reductions in black spot disease symptoms, suggesting that melanization
of appressoria might be a critical factor for the pathogenicity of D. rosae. Our findings were confirmed and validated by the lack of melanized appressorial ring formation on an artificial surface
and on a D. rosae-non host plant system, Arabidopsis thaliana. Our findings suggest that localized melanization of appressoria is a crucial factor for the pathogenicity of D. rosae and treatment of the fungus with MBIs seems to be a promising disease management alternative for black spot disease of roses. 相似文献
6.
Wanying Zhang Haiyang Li Limin Wang Shunpei Xie Yuan Zhang Ruijiao Kang Mengjuan Zhang Panpan Zhang Yonghui Li Yanfeng Hu Min Wang Linlin Chen Hongxia Yuan Shengli Ding Honglian Li 《Molecular Plant Pathology》2022,23(2):218-236
The hemibiotrophic pathogen Bipolaris sorokiniana causes root rot, leaf blotching, and black embryos in wheat and barley worldwide, resulting in significant yield and quality reductions. However, the mechanism underlying the host–pathogen interactions between B. sorokiniana and wheat or barley remains unknown. The B. sorokiniana genome encodes a large number of uncharacterized putative effector proteins. In this study, we identified a putative secreted protein, CsSp1, with a classic N-terminal signal peptide, that is induced during early infection. A split-marker approach was used to knock out CsSP1 in the Lankao 9-3 strain. Compared with the wild type, the deletion mutant ∆Cssp1 displayed less radial growth on potato dextrose agar plates and produced fewer spores, and complementary transformation completely restored the phenotype of the deletion mutant to that of the wild type. The pathogenicity of the deletion mutant in wheat was attenuated even though appressoria still penetrated the host. Additionally, the infectious hyphae in the deletion mutant became swollen and exhibited reduced growth in plant cells. The signal peptide of CsSp1 was functionally verified through a yeast YTK12 secretion system. Transient expression of CsSp1 in Nicotiana benthamiana inhibited lesion formation caused by Phytophthora capsici. Moreover, CsSp1 localized in the nucleus and cytoplasm of plant cells. In B. sorokiniana-infected wheat leaves, the salicylic acid-regulated genes TaPAL, TaPR1, and TaPR2 were down-regulated in the ∆Cssp1 strain compared with the wild-type strain under the same conditions. Therefore, CsSp1 is a virulence effector and is involved in triggering host immunity. 相似文献
7.
The development of the leaves of 8 mutants ofOenothera hookeri is compared with that of the normal type. All mutants show differences from the controls in many characters, which are interconnected by developmental processes in the sense of a relational pleiotropy (Hadorn). In this paper, quantitative observations on growth characteristics are described. Differences between the mutants and the control do not only exist in the size of mature leaves, but also in the changes of size and form of the leaves during the period of growth.Size and form of leaves are described by arithmetic mean and variance for length and width, and by the length to width ratio. Comparison of growth curves and regression-coefficients as a measure of growth rate of the mutants showed significant differences from wild type. The growth in length and width differs not always in the same direction from the normal.In the mutantsSp-1, gi-2 andb differences in growth curves were found even for leaves, which did not show a deviation in size or form from normal ones.In normal leaves the epidermal cells near the tip of the leaves are smaller than those in the middle part. The cells are smaller in the stemleaves compared with the rosettes. All mutants,gi-2 excepted, show differences in cell size compared with the normal form.The relation of cell size to length and width of the leaves showed that growth by cell division is, in all eight mutants investigated, different from normal. 相似文献
8.
Detection of an elicitor on infection structures of Puccinia graminis using monoclonal antibodies 总被引:1,自引:0,他引:1
R Tiburzy U C Rogner R Fischer B Beissmann F M Kreuzaler H J Reisener 《European journal of cell biology》1991,55(1):174-178
The basidiomycetous fungus Puccinia graminis f. sp. tritici causes the stem rust disease of wheat. Resistance of wheat to the fungus is often associated with the hypersensitive reaction of infected host cells. A glycoprotein isolated from germ tube cell walls of the pathogen elicits a hypersensitive-like response when injected into wheat leaves. Infection structures morphologically identical to those grown on wheat were induced in the absence of the host plant, and indirect immunofluorescence together with specific monoclonal antibodies to the elicitor was employed to locate the antigen at fungal infection structures. No binding occurred to germ tubes or appressoria. The antibodies located the antigen only at that part of the fungal infection structure that develops endophytically in nature and, moreover, only at the youngest part of this structure. In rust-infected wheat leaves, the immunolabel appeared only at haustoria, the structures thought to be involved in specific recognition between host and parasite. 相似文献
9.
Colletotrichum truncatum isolate NRRL 13737 (ARS patent culture No. 18434) is being evaluated for development as a mycoherbicide against the problematic weed Sesbania exaltata. Studies were conducted to determine whether selected phylloplane microorganisms, used as coinoculants, could increase the severity of disease incited by C. truncatum in S. exaltata. Hemp Sesbania seedlings were grown in a variety of soils and environments, sprayed with conidia of C. truncatum, and the formation of appressoria was examined on leaves using epifluorescence microscopy. From hemp sesbania plants that supported high levels of appressoria formation, over 200 phyllosphere microorganisms were isolated. Fifteen of 73 microbial isolates assayed stimulated appressoria formation in vitro on cellophane membranes. Five of 8 superior isolates from the in vitro assay also enhanced disease symptoms induced by C. truncatum on S. exaltata compared to seedlings treated with conidia only. Populations of three selected superior isolates remained high on leaves during plant exposure to dew. The superior isolates initiated no apparent symptoms and rarely decreased seedling growth parameters in the absence of C. truncatum. This is the first instance of utilizing phylloplane microorganisms to increase the level of disease incited by a mycoherbicide agent. Microbial facilitators may provide a means of improving the weed control efficacy of mycoherbicides. 相似文献
10.
Background
In order to initiate plant infection, fungal spores must germinate and penetrate into the host plant. Many fungal species differentiate specialized infection structures called appressoria on the host surface, which are essential for successful pathogenic development. In the model plant pathogen Magnaporthe grisea completion of mitosis and autophagy cell death of the spore are necessary for appressoria-mediated plant infection; blocking of mitosis prevents appressoria formation, and prevention of autophagy cell death results in non-functional appressoria. 相似文献11.
G. N. Mishina M. N. Talieva A. V. Babosha G. V. Serezhkina L. N. Andreev 《Biology Bulletin》2002,29(1):46-52
We studied the role of phytohormones: zeatin, kinetin, and abscisic acid, in the regulation of development of the conidial inoculum of Erysiphe cichoracearumDC. f. phlogisJacz. and E. graminisDC. f. hordeiMarchal. When the pathogen conidia were in direct contact with phytohormones, the intensity of their germination significantly increased. In the presence of cytokinins, the amount of normal appressoria decreased and that of abnormal growth tubes increased. On the phlox leaves treated with cytokinins, the intensity of germination of the conidia increased, as compared to the control, while abscisic acid exerted the opposite effect. The treatment of barley leaves with cytokinins did not affect markedly the development of conidial inoculum, as compared to the control, while abscisic acid significantly decreased the intensity of germination of the conidia. On the leaves of different Phloxspecies, the degree of germination of the conidial negative correlated with their resistance against the powdery mildew. The role of cytokinins in pathogenesis of biotrophic fungi is discussed. 相似文献
12.
Christine Tayeh Béatrice RandouxNatacha Bourdon Philippe Reignault 《Journal of plant physiology》2013
Heptanoyl salicylic acid (HSA) is a salicylic acid (SA) derivative obtained by esterification of 2-OH benzoic acid with heptanoic acid. In wheat, the protection levels obtained against Blumeria graminis f. sp. tritici (Bgt) increased from 50% with SA to 95% with HSA. Using molecular, biochemical and cytological approaches, we investigated here how wheat lipid metabolism is differentially activated by SA and HSA in both infectious and non-infectious conditions, and how Bgt infectious process is altered by both inducers. First, in the absence of Bgt, continuous lipoxygenase (LOX)-encoding gene expression and corresponding activity were specifically induced by HSA. Moreover, compared to SA, HSA treatment resulted in earlier up-regulations of the phospholipase C2-encoding gene expression and it specifically affected the expression of a lipid transfer protein-encoding gene. In infectious context, both HSA and SA sprayings impaired penetration events and therefore haustorium formation, leading to less frequent fungal colonies. While this alteration only slowed down the evolution of Bgt infectious process in SA-sprayed leaves, it completely impaired the establishment of successful infectious events in HSA-sprayed leaves. In addition, HSA induced continuous increases of a LOX-encoding gene expression and of the corresponding LOX activity when compared to SA-sprayed leaves. Lipid metabolism is therefore overall highly responsive to HSA spraying and could represent effective defence mechanism triggered during the induction of resistance in wheat toward Bgt. The concepts of priming and energy costs of the defences induced by SA and HSA are also discussed. 相似文献
13.
Ascospores of Sclerotinia sclerotiorum infected fully expanded sunflower leaves in the absence of added nutrients, wounds or senescent tissue. The site of infection was confined to a specific region around the junction of the leaf blade and the petiole and was associated with sites of sucrose secretion by the host. In these areas ascospores germinated and formed extensive colonies on the leaf surface. Simple appressoria were visible at 24 h, and complex appressoria at 48 h, after inoculation. Ascospores that germinated in areas where sucrose was not secreted produced germtubes that were shorter (less than 50 μm at 48 h after inoculation) than those produced at sites where sucrose was secreted (greater than 5 mm in length). Infections also developed on severely wounded main leaf veins. Leaf wetness was required for infection, with maximal infection occurring after a 72 h dew period. 相似文献
14.
Jinrong Yin Chaofeng Hao Gang Niu Wei Wang Guanghui Wang Ping Xiang Jin-Rong Xu Xue Zhang 《Environmental microbiology》2020,22(12):5373-5386
Ascospores are the primary inoculum in Fusarium graminearum, a causal agent of wheat head blight. In a previous study, FgPAL1 was found to be upregulated in the Fgama1 mutant and important for ascosporogenesis. However, the biological function of this well-conserved gene in filamentous ascomycetes is not clear. In this study, we characterized its functions in growth, differentiation and pathogenesis. The Fgpal1 mutant had severe growth defects and often displayed abnormal hyphal tips. It was defective in infectious growth in rachis tissues and spreading in wheat heads. The Fgpal1 mutant produced conidia with fewer septa and more nuclei per compartment than the wild type. In actively growing hyphal tips, FgPal1-GFP mainly localized to the subapical collar and septa. The FgPal1 and LifeAct partially co-localized at the subapical region in an interdependent manner. The Fgpal1 mutant was normal in meiosis with eight nuclei in developing asci but most asci were aborted. Taken together, our results showed that FgPal1 plays a role in maintaining polarized tip growth and coordination between nuclear division and cytokinesis, and it is also important for infectious growth and developments of ascospores by the free cell formation process. 相似文献
15.
Yoshihiro Takikawa Koji Kakutani Teruo Nonomura Yoshinori Matsuda Hideyoshi Toyoda 《Mycoscience》2011,52(3):204-209
In the present study, using a high-fidelity digital microscope, we observed the sequence of appressorial development on the
germ tubes of a powdery mildew fungus isolated from red clover leaves. Based on its morphological characteristics and rDNA
internal transcribed spacer (ITS) sequences, the fungus was identified as Erysiphe trifoliorum, and one of its isolates, designated as KRCP-4N, was used in this work. The conidial germination of isolate KRCP-4N was studied
on host (red clover) and non-host (barley) leaves, as well as on an artificial hydrophobic membrane (Parafilm). More than
90% of conidia germinated synchronously and developed dichotomous appressoria (symmetrical double-headed appressoria) on all
substrata used. On host leaves, all appressorium-forming conidia developed hyphae (colony-forming hyphae) from conidial bodies
without extending germ tubes from the tips of the appressoria. On non-host leaves and on Parafilm-covered glass slides, however,
all conidia extended germ tubes from one side of dichotomous appressoria (two-step germination). In addition to the dichotomous
appressoria, we detected a few conidia that produced hooked appressoria and extended germ tubes from the tip of the appressorium.
Penetration attempts by KRCP-4N conidia on barley leaves were impeded by papillae formed at penetration sites beneath these
two types of appressorium. From these results, we conclude that the “two-step germination” of E. trifoliorum KRCP-4N conidia is the result of an unsuccessful penetration attempt, causing diversity in appressorial shape. 相似文献
16.
Modes of branching of appressoria on conidial germ tubes of 36 Erysiphe spp. were studied. Only unlobed appressoria, termed alobatus pattern, were seen in E. lonicerae, E. magnifica and E. symphoricarpi. Viewed from above with light or scanning electron microscopes, other species had ± irregular lobing, but from below in the
plane of contact with the substrate successive dichotomous branchings at 120° were seen to produce a five-lobed appressorium
within 6 h. Each division produced a temporarily dormant outward-facing lobe and an inward limb that continued growth and
division to form the axis of curved, hooked, single- or double-headed symmetrical or asymmetrical structures in a helicoid
cyme-like pattern. Outlines of extracellular material after removal of germinated conidia confirmed this manner of branching.
After 36 h some lobes re-divided forming botryose or jigsaw patterns even extending with extra appressoria to form candelabra-like
structures. Conidia developed only one true germ tube; rarely secondary unswollen tubes emerged from spare shoulders or ends.
The same true germ tubes developed initially on host surfaces, where secondary tubes and/or extensions from appressorial lobes
grew into colony-forming hyphae. Lobed appressoria of Neoerysphe and Phyllactinia also branched at 120°. Podosphaera xanthii exhibited a simpler branching pattern. 相似文献
17.
Plotnikova LIa 《Tsitologiia》2008,50(5):439-446
Parasitic rust fungi Puccinia triticina and P. coronata specialized to cereals are not able to form functionally completed cellular structures (germ tubes and appressoria) on the surface of plant species that do not belong to Poaceae. Fungus structures are induced by the surface features of grains leaves (millet, maize, oat, common wheat) to a different extent. Nuclear division and activity of parasites are partially suppressed on the non-host leaves. Fungi intrusions into sub-stomal cavities of the oat and wheat leaves are predominantly prevented by oxidative burst and to the less extent by defense proteins. 相似文献
18.
MoCDC14 is important for septation during conidiation and appressorium formation in Magnaporthe oryzae
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Chaohui Li Shulin Cao Chengkang Zhang Yonghui Zhang Qiang Zhang Jin‐Rong Xu Chenfang Wang 《Molecular Plant Pathology》2018,19(2):328-340
As a typical foliar pathogen, appressorium formation and penetration are critical steps in the infection cycle of Magnaporthe oryzae. Because appressorium formation and penetration are closely co‐regulated with the cell cycle, and Cdc14 phosphatases have an antagonistic relationship with cyclin‐dependent kinases (CDKs) on proteins related to mitotic exit and cytokinesis, in this study, we functionally characterized the MoCDC14 gene in M. oryzae. The Mocdc14 deletion mutant showed significantly reduced growth rate and conidiation. It was also defective in septum formation and nuclear distribution. Septation was irregular in Mocdc14 hyphae and hyphal compartments became multi‐nucleate. Mutant conidia often showed incomplete septa or lacked any septum. During appressorium formation, the septum delimiting appressoria from the rest of the germ tubes was often formed far away from the neck of the appressoria or not formed at all. Unlike the wild‐type, some mutant appressoria had more than one nucleus at 24 h. In addition to appressoria, melanization occurred on parts of the germ tubes and conidia, depending on the irregular position of the appressorium‐delimiting septum. The Mocdc14 mutant was also defective in glycogen degradation during appressorium formation and appressorial penetration of intact plant cells. Similar defects in septum formation, melanization and penetration were observed with appressorium‐like structures formed at hyphal tips in the Mocdc14 mutant. Often a long fragment of mutant hyphae was melanized, together with the apical appressorium‐like structures. These results indicate that MoCDC14 plays a critical role in septation, nuclear distribution and pathogenesis in M. oryzae, and correct septum formation during conidiogenesis and appressorium formation requires the MoCdc14 phosphatase. 相似文献
19.
Growth promotion and an increase in cell wall extensibility by silicon in rice and some other Poaceae seedlings 总被引:6,自引:0,他引:6
M. T. Hossain R. Mori K. Soga K. Wakabayashi S. Kamisaka S. Fujii R. Yamamoto T. Hoson 《Journal of plant research》2002,115(1):0023-0027
The effect of silicon on organ growth and its mechanisms of action were studied in rice (Oryza sativa L. cv. Koshihikari), oat (Avena sativa L. cv. Victory), and wheat (Triticum aestivum L. cv. Daichino-Minori) seedlings grown in the dark. Applying silicon in the form of silicic acid to these seedlings via
culture solution resulted in growth promotion of third (rice) or second (oat and wheat) leaves. The optimal concentration
of silicon was 5–10 mM. No growth promotion was observed in early organs, such as coleoptiles or first leaves. In silicon-treated
rice third leaves, the epidermal cell length increased, especially in the basal regions, without any effect on the number
of cells, showing that silicon promoted cell elongation but not cell division. Silicon also increased the cell wall extensibility
significantly in the basal regions of rice third leaves. These results indicate that silicon stimulates growth of rice and
some other Poaceae leaves by increasing cell wall extensibility.
Received: July 31, 2001 / Accepted: September 18, 2001 相似文献
20.
The powdery mildew caused by Oidium lycopersici is one of the most destructive diseases in glass-house-grown tomato and is widespreading all over the world. A high level
of resistance to O. lycopersici was found in an accession of Lycopersicon esculentum var. cerasiforme at the Department of Biology and Plant Pathology, University of Bari. The genetic analysis of F1, F2 and BC plants indicated
that the resistance is conferred by a single recessive gene, designed as ol-2. Studies on the infection process of O. lycopersici on susceptible and ol-2 gene resistant tomatoes were carried out at 24 °C and 90 % relative humidity. Light microscope observations on conidia germination,
formation of primary appressoria, elongation of hyphae and sporulation were made on artificially inoculated basal, intermediate
and apical leaves. Inoculation was made by shaking mildewed tomato leaves over each test plant. Disease development were assessed
by removing the fungal structure from the leaf surface with the ceroidin film technique and by direct observations of stained
inoculated leaves. The rate of conidial germination and the appressoria formation was not affected by host genotype. Mycelia
growth and sporulation on leaf surface of resistant plant was strongly restricted and influenced by the leaf age. The results
indicated that the resistance in ol-2 tomato is postinfectional and is not associated with a hypersensitive response.
This work was supported by the MURST and CNR (Paper no. 331) 相似文献