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1.
The extent to which uranyl ions and peroxidase permeated haustorial complexes isolated from Pisum sativum infected with Erysiphe pisi was determined by transmission electron microscopy (TEM).Freshly isolated complexes were treated with uranyl acetate, either directly, or after treatment with cell wall degrading enzymes, or with Triton X-100 and the uranyl ion, precipitated with phosphate. The complexes were then fixed with glutaraldehyde and examined by TEM to determine the distribution of uranyl phosphate crystals.Two independent experiments, each involving the examination of 80 complexes, gave similar results. After direct uranyl treatment, crystals were excluded from 38% of the complexes, were present in the extrahaustorial matrix only in 19% and occurred throughout in 43%. Breaks were observed in the extrahaustorial membrane of the last two categories. Uranyl crystals bound to the outer (host cytoplasmic) surface of the extrahaustorial membrane and also to the matrical surface, where this was accessible. In addition, the few necrotic haustorial complexes observed were completely permeated.Following pre-treatments with pectinase and cellulase, or Triton X-100, uranyl crystals were present throughout the complexes in all or 96%, of the complexes respectively.In similar experiments involving treatment with horseradish peroxidase (instead of uranyl acetate) followed by the addition of hydrogen peroxide and 3,3-diaminobenzidene, electron opaque deposit occurred around the complexes but never internally in any part of them. Even where breaks in the extrahaustorial membrane were visible the extrahaustorial matrix was not permeated.It is concluded that the extrahaustorial membrane and haustorial plasma membrane are semipermeable in many of the isolated haustorial complexes but that some are damaged during isolation and purification procedures; that a barrier to diffusion exists where the extrahaustorial membrane is joined to the wall of the haustorial neck and in other parts of the neck wall so that the whole boundary of the extrahaustorial matrix restricts diffusion of solutes; and that the extrahaustorial matrix is a gel which precludes the passage of large molecules through it. The physiological implications of the results are discussed. 相似文献
2.
小麦新抗源一粒葡抗条锈病的组织学和超微结构研究 总被引：1，自引：0，他引：1
采用荧光显微镜、微分干涉显微镜和电子显微镜技术,系统研究了小麦新抗源一粒葡抗小麦条锈病的组织学和超微结构特征。结果表明:相对于感病品种铭贤169,一粒葡对条锈菌的侵染,在组织学和超微结构上均表现出明显的抗性特征。在组织学水平,表现为菌丝生长受抑,菌落发育延迟或败育,吸器母细胞和吸器数目明显减少;同时,侵染点的寄主细胞表现出不同程度的过敏性坏死症状。电镜观察发现,在一粒葡和感病品种中,条锈菌均可由芽管顶端直接进入或通过形成附着胞进入小麦气孔。其后,在一粒葡上,病菌胞间菌丝、吸器母细胞、吸器在细胞和亚细胞水平均发生了一系列异常变化,表现为原生质染色逐渐加深,液泡增多变大,逐渐消解原生质;胞间菌丝、吸器母细胞细胞壁不规则增厚;胞间菌丝线粒体肿胀,数目增多,逐渐解体;吸器母细胞细胞质逐渐空泡化后丧失其生理功能;吸器外质膜皱褶;吸器外间质加宽并有丝状或颗粒状物质形成,吸器体壁逐渐消解出现孔洞,吸器体最终畸形坏死。同时,寄主细胞产生一系列显著的结构防卫反应:形成胞壁沉积物、乳突、吸器鞘等结构,以及发生坏死,阻碍并抑制病菌的发育及扩展。 相似文献
3.
小麦与条锈病菌不亲和互作的超微结构 总被引：9，自引：1，他引：9
采用条锈菌同一小种的野生型菌系和弱毒突变菌系,分别接种同一小麦品种的方法,研究了不亲和互作的超微结构特征。在不亲和互作中,条锈菌的胞间菌丝、吸器母细胞和吸器明显受抑。吸器可以在发育早期受抑坏死,也可迟滞至吸器体形成之后坏死。吸器外质膜严重皱褶,并出现孔洞,吸器外间质加宽,沉积大量电子致密物质。侵染位点的小麦叶肉细胞表现与过敏性坏死反应相关联的一系列变化。细胞壁内侧还出现乳突状或颗粒状沉积物等防御结构或物质。 相似文献
4.
Yeon Kyeong Lee Jeum Kyu Hong Sigrun Hippe-Sanwald Byung Kook Hwang 《Physiological and Molecular Plant Pathology》2000,57(6)
The compatible interaction of pepper stems with Phytophthora capsici showed more rapid and severe disease development than did the incompatible interaction, although pathogen penetration styles of host cells in compatible and incompatible interactions were similar to each other. Treatment with
-β-amino- n -butyric acid (BABA) protected the pepper plants against P. capsici infection. Reduced hyphal growth and sporangial formation were found after P. capsici infection in BABA-induced resistant and incompatible reactions. One of the most noticeable ultrastructural features of the BABA-induced resistant reaction was the formation of electron-dense wall appositions. The thick and dense wall appositions that encased the haustoria restricted haustorial development, thus leading to limitation of further pathogen penetration into inner plant tissues. A main host response in the incompatible interaction was the occlusion of cortical cells with an amorphous material. Plugging of the intercellular spaces in the cortical cells with electron opaque material was frequently observed in the incompatible interaction, but not in the compatible interaction. Another common feature of the BABA-induced resistant and incompatible reactions was degeneration of mitochondrial structure within penetrating hyphal cytoplasm. The mitochondrial structure in the BABA-induced resistant or incompatible reactions had no distinct double membrane layer and well-shaped cristae. 相似文献
5.
寡聚糖诱导黄瓜对白粉病抗病反应的超微结构研究 总被引：13，自引：0，他引：13
中科6号(2%氨基寡糖素)处理黄瓜植株叶片,5 d后接种白粉菌Sphaerotheca fuliginea(Schlecht.) Poll.,可诱导黄瓜Cucumis sativus产生对白粉病的抗病性,寄主细胞对病原菌的侵入产生了防卫反应结构和物质以及过敏性坏死反应。表现为寄主细胞壁加厚,染色加深,寄主细胞壁下产生多层次结构的乳突,在寄主细胞壁与质膜之间有黑色物质沉积;吸器外质膜皱褶,染色加深,吸器外基质中出现染色加深的颗粒状电子沉积物;寄主细胞质紊乱,细胞器解体,整个寄主细胞解体、坏死。 相似文献
6.
Byung Kook Hwang Firous Ebrahim-Nesbat Wolf-Dieter Ibenthal Rudolf Heitefuss 《Pest management science》1990,29(2):151-162
Stems of pepper seedlings were inoculated with zoospores of Phytophthora capsici 18 h after a soil-drench with metalaxyl solution (5 μg ml?1) or water. Infected stem tissues were examined by electron microscopy 24 h after inoculation. Compared with untreated controls, in which the fungal cells were generally normal in shape and ultrastructure, the most conspicuous effects of metalaxyl treatment on the fungal ultrastructure in the stem tissue were an abnormal shrinking of the fungal cell, a separation of the plasma membrane from the hyphal wall, a peculiar invagination and breakdown of the plasma membrane, the presence of vesicles in the invaginated spaces and within the damaged fungal cells, and an indistinct structure of cell organelles. In metalaxyl-treated stems, an electron-dense material was apposed in those sites of the host cell wall in most intimate contact with the fungal cell wall, indicating that the deposition of these substances from the host cell walls may function as a plant defence reaction to the fungus, whereas in untreated controls, the dark-stained host cytoplasm did not aggregate around the sites of fungal contact. The haustorium was encased by the extra-haustorial matrix in treated stems. These results suggest that metalaxyl treatment not only changes the fine structure of P. capsici, but may also induce the plant defence reaction. 相似文献
7.
Preventive application of bromuconazole caused reduction in size and increased encasement rate of haustoria of Erysiphe graminis DC. For example, seven days after inoculation, 60 and 70% of haustoria had been encased in leaves treated with 8 mg litre−1 and 16 mg litre−1 respectively; the average length of the digitations was 8–10 μm in treated cells compared to 24 μm in untreated cells. The encasement process extended from the neck region to the whole haustorium. Haustorial bodies from treated plants had electron-dense cytoplasm and their organelles were more difficult to identify than in control plants. Extrahaustorial matrix was reduced to an unusually thin, osmiophilic pellicle, surrounded by abundant heterogeneous encasement material. Curative treatment induced similar changes, especially in the margin of the colonies. In the centre of the colony, haustoria were less affected by the fungicide; deposition of collar-like material, modification of extrahaustorial matrix and membrane and accumulation of plant cytoplasm around the digitations resulted in an intermediate, ‘swollen’ state of digitate haustoria. The possible pathway of encasement events is discussed. 相似文献
8.
9.
David J. McNally Kirstin V. Wurms Caroline Labb Richard R. Blanger 《Physiological and Molecular Plant Pathology》2003,63(6):293-303
Leaf tissue harvested from cucumber plants (Cucumis sativus L.) expressing induced resistance against the powdery mildew fungus Podosphaera xanthii (syn. Sphaerotheca fuliginea, Castagne; Braun and Shishkoff) was extracted and analyzed for phytoalexin compounds. Fluorescence microscopy was then used to observe the production of these compounds in planta, and laser scanning confocal microscopy observations were made to locate the subcellular sites of phytoalexin accumulation. Phytochemical analyses and fluorescence microscopy observations revealed the production of autofluorescent C-glycosyl flavonoid phytoalexins within the epidermal tissues of disease-resistant plants undergoing fungal ingress. Phytoalexin production was triggered by the combination of an eliciting/inoculation treatment, and tissue autofluorescence of color characteristic of the phytoalexins reached a maximum 48 h after elicitation prior to subsiding following the collapse of the pathogen. After a second eliciting treatment, disease-resistant plants produced phytoalexins more rapidly in response to fungal challenge. At the cellular level, autofluorescent C-glycosyl flavonoid phytoalexins were observed associated with the plasma membrane of infected epidermal cells immediately following elicitation. In the hours that preceded the collapse of conidial chains, phytoalexins accumulated inside the haustorial complexes of the pathogen within the epidermal cells of disease-resistant plants. Taken together, the results of this study show the timely synthesis of C-glycosyl flavonoid phytoalexins at precise subcellular locations as a key defense reaction used by cucumber to create incompatible interactions with powdery mildew. 相似文献
10.
No correlation was found between the chitosan or Fusarium solani-induced disease resistance responses in pea pod tissue and fluctuations in [Ca2+], inhibition of calmodulin, blockage of Ca2+ channels or host membrane leakage. Addition of exogenous Ca2+ 3 h before or after chitosan or F. solani treatments of pea pod tissue failed to alter the host response within 6 h, the time when the host actively resists both the compatible (F. solani f. sp. pisi) and incompatible (F. solani f. sp. phaseoli) macroconidia. Additionally, Ca2+ applied exogenously 3 h before or after chitosan significantly altered the level of UV-absorbing material released from the host tissue; however, it failed to affect the chitosan's ability to elicit phytoalexin formation by 24 h. Addition of exogenous Ca2+ 3 h before or after inoculation with either the compatible (f. sp. pisi) or incompatible (f. sp. phaseoli) fungi did not significantly change the host response by 24 h. The addition of EGTA or Ca2+ channel antagonists with the chitosan treatments also failed to significantly alter the chitosan-induced host response, thereby suggesting that chitosan probably does not function in the pea system by causing a Ca2+ influx into the host tissue which might then activate the host's resistance response. Inhibition of calmodulin related activities by calmidazolium failed to inhibit the chitosan or fungal induced host response. These results suggest that the response(s) induced in pea pod tissue by chitosan treatment or fungal inoculation may not be mediated by Ca2+, calmodulin or membrane leakage. 相似文献
11.
The interface between Erysiphe pisi and pea cv. JI 1049 was studied at the ultrastructural and cytochemical levels and compared with those in two susceptible cultivars. Haustorial efficiencies, as indexed by the length of mycelium associated with each haustorium, and growth rates on the resistant and one susceptible cultivar were also compared.The interaction in the resistant cultivar differed from those in the susceptible cultivars in the following ways: (i) there was no contact between the host plasmalemma and the A neckband region; (ii) papillae were contiguous with the surface of the neck and thus were probably formed before haustoria and (iii) there appeared to be less polysaccharide in the extrahaustorial membrane. The extrahaustorial membrane in the resistant cultivar lacked ATPase activity, whereas the rest of the host plasmamembrane had normal activity.Each haustorium supported a significantly greater total hyphal length in the resistant than in the susceptible cultivars. Growth rates of superficial hyphae were very similar on the susceptible and resistant cultivars but there was a delay in the onset on hyphal growth on the resistant cultivar which correlated with the previously reported delay in formation of the first haustorium. In contrast to hyphal growth rates, the rate of haustorium production was significantly less in the resistant cultivar. It is proposed that resistance in cv. JI 1049 operates at the stages prior to haustorium formation, similarly to that in some non-host and partial resistance systems. Once formed, however, the function of the haustorium seems to be unimpaired, despite the observed interfacial differences. 相似文献
12.
The distribution of N-acetylglucosamine residues in the cell wall of the white-rot pathogenic fungus, Rigidoporus lignosus, was studied by using gold labelled wheatgerm agglutinin bound to ovomucoid-colloidal gold. Ultrastructural investigation of R. lignosus-infected root tissues of Hevea brasiliensis showed a modification of the fungal cell wall throughout the infection process. Gold particles were found to occur on both thick- and thin-walled hyphae of R. lignosus rhizomorphs at the root surface. Walls of hyphae that had penetrated the roots were only labelled when they were out of the host cell, suggesting that modification of chitin molecules may be related to the excretion of host cell wall degrading enzymes. Variation in the distribution of gold particles was observed over hyphal walls of both colonized phellem and xylem cells. The observation that N-acetylglucosamine residues were released in the host cell cytoplasm suggests that lytic enzymes alter the fungal cell walls. Released chitin oligosaccharides may play a role in the induction of the root's defence system against fungal attack. 相似文献
13.
Fusarium species are soil-borne fungal pathogens that produce a variety of disease symptoms when attacking crop plants. The mode of root colonization of Eucalyptus viminalis seedlings by a pathogenic F. oxyporum strain (Foeu1) at the ultrastructural level and changes in cell wall pectin during host pathogen interactions are described. Root systems of E. viminalis plants were inoculated with F. oxysporum in an in vitro model system. Hyphae of F. oxysporum adhered to the outer epidermal cell walls through fibrillar material, and after penetration they spread into the internal tissues. They developed intercellularly and intracellularly in the root cortex and invaded vascular tissues. Papillae were induced, and the host plasma membrane ruptured in colonized cells, causing rapid host tissue and cell damage. Changes in distribution and occurrence of nonesterified and methyl-esterified pectins were evaluated after root colonization by F. oxysporum using two monoclonal antibodies, JIM 5 and JIM 7, respectively. Nonesterified pectin in control roots was mainly localized in the epidermal cell walls and middle lamellae in parenchymal cortex, whereas methyl-esterified pectin accumulated more in primary cell walls of the cortex and phloem. Decreases in immunodetected nonesterified and methyl-esterified pectins were associated with extensive plant tissue degradation after root colonization by the pathogenic fungus. 相似文献
14.
Angela T. Alleyne Jim R. Steadman Kent M. Eskridge 《European journal of plant pathology / European Foundation for Plant Pathology》2008,122(2):315-319
Corresponding molecular markers associated with avirulence or virulence genes in the bean rust pathogen are currently unknown,
although host resistance genes have been linked to molecular markers in bean. The changing virulence patterns in pathotypes
of Uromyces appendiculatus collected over a 14-year period after the release of the Ur-6 resistance gene on the USA high plains were therefore analyzed using rep-PCR molecular markers. Isolates from two neighbouring
pathotype groups from Colorado and Nebraska were screened using the rep-PCR primer Box-AIR. The PCR fragment Box
475 was cloned and sequenced and a specific primer set ATA-2 was designed. This primer yielded 10 polymorphic products which
allowed separation of these isolates into two distinct groups and will be useful for future analysis of the population genetics
of this organism. 相似文献
15.
在电镜下观察发现,菜豆锈病菌侵染菜豆后,逐步对其超微结构产生影响:寄主细胞发生质壁分离;叶绿体变形;叶绿体的片层结构排列零乱;线粒体脊模糊不清,直至叶绿体解体;线粒体空泡化;少数细胞的细胞壁分解;不同细胞的细胞器堆积在一起。同时,病原菌的侵染激发了寄主抗病性的细胞学表现:供试的抗感菜豆品种都表现为在病原菌侵入位点的寄主细胞壁内侧有高电子致密物质沉积;与吸器母细胞接触的寄主细胞壁加厚以及在吸器颈周围有电子不透明物质形成。只是这3种反应在抗病品种中表现得更加强烈。此外,抗病品种中还有一些特有的抗性特征,如被侵染细胞及其相邻细胞的快速坏死,吸器母细胞侵入位点的寄主细胞壁外侧也有一种高电子致密物质沉积,抗病品种中真菌吸器周围聚集含大量线粒体的寄主细胞的细胞质,且吸器外基质比感病品种中的宽。 相似文献
16.
A-蛋白和羊抗兔血清应用于免疫电镜,检测马铃薯X病毒(PVX)粗汁液,灵敏度比诱捕修饰法高;而且加羊抗兔血清后,病毒粒体比诱捕修饰法明显加粗,在电镜放大2500倍时,就能清晰地观察到。用诱捕双修饰法检测PVX,证实在寄主植物的叶、茎和根中均存在,以叶内含量最高。接种在普通烟上第三天,接种叶就能检测到PVX,接种15天后,寄主体内病毒能达到较高浓度,而且高浓度一直可保持2个月以上;PVX在不同寄主中的含量不同,以普通烟中病毒浓度最高,心叶烟、番茄和黄花烟中次之;昆诺阿藜、千日红和大椒中含毒量极抵。用诱捕双修饰法检测马铃薯薯块休眠芽中的病毒获得成功。 相似文献
17.
Hua Li Xintian Ge Shiue Han Krishnapillai Sivasithamparam Martin John Barbetti 《European journal of plant pathology / European Foundation for Plant Pathology》2011,129(2):221-232
Differences in Hyaloperonospora parasitica development and plant tissue responses were compared for 10 cruciferous hosts (including both resistant and susceptible genotypes),
3 leguminous and 1 graminaceous non-host species. Cotyledons, or true leaves in the case of Triticum aestivum and Pisum sativum, were studied at 2, 8, 24 h and 3, 5, 7 days post inoculation (dpi). The high levels of zoosporangial germination observed
on all species tested, as well as on glass slides, suggested that inhibition of germination did not play a significant role
in distinguishing host versus non-host resistance. During the early stages of infection, at spore germination and host penetration, there was no evidence
of a clear-cut difference between Brassica host species which displayed a hypersensitive, partially resistant or susceptible reaction compared with non-host species.
Haustoria formation was the key infection phase for the establishment of biotrophy. Across all tested species, haustoria were
initiated inside the epidermal cells. However, there were significant differences in the frequency and timing of haustorial
formation and the final size of haustoria among the tested species at early infection stage. Fully developed haustoria were
never observed in Raphanus raphanistrum, Triticum aestivum, Lupinus angustifolius nor Trifolium subterraneum. Instead, the haustorium development appears to abort in the penetrated epidermal cells of these species. Although haustoria
were formed in the epidermal and mesophyll cells of Sinapsis alba and Pisum sativum, subsequent hyphal growth and/or continued haustoria formation were rare or few, respectively. Hypersensitive reaction was
the key resistance response observed among the host and non-host resistant species tested. It is noteworthy that, in the initial
stages of pathogenesis, there was no differentiating point that separated the non-host species from those that were hosts. 相似文献
18.
The infection process of Fusarium avenaceum on wheat spikes and the alteration of cell wall components in the infected host tissue were examined by means of electron microscopy and cytochemical labelling techniques following spray inoculation at growth stage (GS) 65 (mid-flowering). Macroconidia of the pathogen germinated with one to several germ-tubes 6–12 h after inoculation (hai) on host surfaces. The germ-tubes did not penetrate host tissues immediately, but extended and branched on the host surfaces. Hyphal growth on abaxial surfaces of the glume, lemma and palea was scanty 3–4 days after inoculation (dai) and no direct penetration of the outer surfaces of the spikelet was observed. Dense mycelial networks formed on the inner surfaces of the glume, lemma, palea and ovary 36–48 hai. Penetration of the host tissue occurred 36 hai by infection hyphae only on the adaxial surfaces of the glume, lemma, palea and upper part of ovary. The fungus penetrated the cuticle and hyphae extended subcuticularly or between the epidermal wall layers. The subcuticular growth phase was followed by penetration of the epidermal wall, and hyphae spread rapidly inter- and intracellularly in the glume, lemma, palea and ovary. During this necrotrophic colonization phase of the wheat spike, a series of alterations occurred in the host tissues, such as degeneration of cytoplasm and cell organelles, collapse of host cells and disintegration of host cell walls. Immunogold labelling techniques showed that cell walls of spike tissues contained reduced amounts of cellulose, xylan and pectin near intercellular hyphae or infection pegs compared to walls of healthy host tissues. These studies suggest that cell wall degrading enzymes produced by F. avenaceum facilitated rapid colonization of wheat spikes. The different penetration properties of abaxial and adaxial surfaces of the spikelet tissues as well as the two distinct colonization strategies of host tissues by F. avenaceum are discussed. The penetration and colonization behaviour of F. avenaceum in wheat spikelets resembled that of F. culmorum and F. graminearum, although mycotoxins produced by F. avenaceum differed from those of the latter two Fusarium species. 相似文献
19.
20.
Histological studies of the expression of the Lr9, Lr20 and Lr28 alleles for resistance to leaf rust in wheat 总被引：4，自引：1，他引：3
The development of the leaf rust fungus ( Puccinia recondita f.sp. tritici ) in a susceptible cultivar and three other cultivars possessing the Lr9, Lr20 and Lr28 alleles for resistance was studied by light and fluorescence microscopy. Formation of the substomatal vesicle, intercellular hypha and the first haustorial mother cell was unaffected by resistance. Lr9 and Lr28 expression was rapid, first seen as early initiation of hyphal branching at 16 h after inoculation, then reduced haustorial diameters at 19 h. Limited host cell necrosis was seen immediately afterwards. Elongation of intercellular hyphae was reduced between 20 and 24 h, and virtually ceased by about 30 h. Numbers of infection sites with a second haustorial mother cell were briefly higher at 24 h. Reduced hyphal branching and haustorial mother cell numbers were seen at 20–24 h and 36 h respectively. Lr20 expression was not seen until 36 h when reduced hyphal branching was observed, accompanied by extensive host cell necrosis. Reduced haustorial mother cell numbers were detected at 48 h. Findings suggested a secondary role for host cell necrosis in the expression of the Lr9 and Lr28 alleles. Host necrosis may play a determinant role in Lr20- based expression. 相似文献