梨胶锈菌性孢子和锈孢子阶段吸器的超微结构研究

本文对梨胶锈菌性子期和锈子期菌丝吸器的形成方式、吸器及其与寄主细胞界面的超微结构进行了研究。观察结果表明：梨胶锈菌性子期和锈子期寄主胞间菌丝吸器的形成方式有两种：一种是由寄主胞间菌丝直接形成吸器;另一种是由寄主胞间菌丝先形成吸器母细胞,然后由吸器母细胞形成吸器。吸器在开始形成时只是一个乳头状的侵入楔,以后逐渐形成囊状、镰刀状、指状及其它不规则形状的吸器。多数吸器分化为颈和吸器主体两部分,在颈部及部分吸器主体外有一个由类似寄主细胞壁物质形成的领圈。吸器内部的超微结构与寄主胞间菌丝基本相同,但吸器壁比胞间菌丝或吸器母细胞的壁薄。吸器鞘的厚度随着吸器伸长膨大 而逐渐增厚。     

Ultrastructural characterisation of the host–pathogen interface in white blister-infected Arabidopsis leaves

In this study transmission electron microscopy (TEM) was used to examine details of the host–pathogen interface in Arabidopsis thaliana cotyledons infected by Albugo candida, causal agent of white blister. After successful entry through stomatal pores, the pathogen developed a substomatal vesicle and subsequently produced intercellular hyphae. TEM observations revealed that coenocytic intercellular hyphae ramified and spread intercellularly throughout the host tissue forming several haustoria in host mesophyll cells. Intracellular haustoria were spherical and 4.5 μm in diameter. Each haustorium was connected to intercellular hyphae by a narrow, slender haustorium neck. The cytoplasm of the haustorium included the organelles characteristic of the pathogen. No obvious response was observed in host cells following formation of haustoria. Most of the mesophyll cells contained normal haustoria and the host cytoplasm displayed a high degree of structural integrity. Absence of host cell wall alteration and cell death in penetrated host cells suggest that the pathogen exerts considerable control over basic cellular processes and in this respect, response to this biotrophic Oomycete differs considerably from responses to other pathogens such as necrotrophs. Modification of the host plasma membrane (PM) along the cell wall and around the haustoria, was detected by applying the periodic acid-chromic acid-phosphotungstic acid (PACP) staining technique. After staining with PACP, the host PM was found to be intensely electron dense where it was adjacent to the host cell wall and the distal region of the haustorial neck. By contrast, the extrahaustorial membrane, where the host PM surrounded the haustorium, was consistently very lightly stained.     

Ultrastructural Studies of the Intercellular Hypha aud Haustorium of Puccinia recondita f.sp. tritici

The ultrastructure of intercellular hyphae and D-hati-storia of P. recondita f.sp. tritici, and the host response to haustorial invasion, was investigated. The intercellular hyphae share common characteristics with those of other uredial stage rust fungi. Anastomosis was observed between intercellular hyphae. Two nucleoli were frequently observed in a single nucleus in the haustorium, indicating possible nuclear fusion between the two nuclei in D-haustoria of this fungus. The close association of host organelles, such as the nucleus, Golgi bodies, endo-plasmic reticulum, vesicles and mitochondria, with the developing haustorium, is described.     

THE HOST-PARASITE INTERFACE OF ALBUGO CANDIDA ON RAPHANUS SATIVUS

The fine structure of the intercellular hyphae of the obligate parasite Albugo candida infecting radish does not differ markedly from that described previously for cells of Peronospora manshurica. The stalked, capitate haustoria do not contain nuclei and are packed with mitochondria and lomasomes. The fungal plasma membrane and cell wall are continuous from the intercellular hypha throughout the haustorium except that there is no evidence of fungal cell wall around a portion of the haustorial stalk proximal to the haustorial head. Within the vacuolate host mesophyll cell, the haustorium is always surrounded by host plasma membrane and with at least a thin layer of host cytoplasm. The host cell wall invaginates at the point of haustorial penetration to form a short sheath around the region of penetration, but normally there is no host cell wall around the balance of the haustorium. About 1% of the haustoria observed were necrotic, and these were invariably walled-off completely from host cytoplasm by host cell wall. An amorphous, moderately electron-dense encapsulation lies between the haustorium proper and the host plasma membrane and extends into the penetration region between the sheath and the fungal cell wall. Invaded host cells contain more ribosomal-rich ground cytoplasm than uninfected cells. Glandular-like systems of tubules and connecting vesicles are often numerous in host cytoplasm in the vicinity of haustorial heads. These tubules open into the encapsulation, their limiting unit membranes being continuous with the host plasma membrane. We suggest that these represent a secretory mechanism of the host specifically induced by the parasite.     

Light and Electron Microscopy of the Compatible Interaction Between Arabidopsis and the Downy Mildew Pathogen Peronospora parasitica

In this study, we focused on compatible interactions between Peronospora parasitica isolate Emoy‐2 and wild‐type (Oy‐0) and mutant (Ws‐eds1) Arabidopsis thaliana accessions by using light and transmission electron microscopy (TEM). Light microscopy of compatible interactions revealed that conidia germinated and penetrated through the anticlinal cell walls of two epidermal cells. Rapid spreading of the hyphal growth with formation of numerous haustoria within the mesophyll cells was subsequently followed by profuse sporulation in the absence of host cell necrosis on both wild‐type and mutant accessions. TEM observations revealed that coenocytic intercellular hyphae ramified and spread intercellularly throughout the host tissue forming several haustoria in host mesophyll cells. Intracellular haustoria were lobed with the diameter of 6–7 μm. Each haustorium was connected to intercellular hyphae in the absence of apparent haustorial neck. The cytoplasm of the haustorium included the organelles characteristic of the pathogen. Callose‐like deposits were frequently observed at sites of penetration around the proximal region of the haustorial neck. Apart from a few callose ensheatments, no obvious response was observed in host cells following formation of haustoria. Most of mesophyll cells contained normal haustoria and the host cytoplasm displayed a high degree of structural integrity. Absence of host cell wall alteration and cell death in penetrated host cell of both accessions suggest that the pathogen exerts considerable control over basic cellular processes and in this respect, response to this biotroph oomycete differs considerably from responses to other pathogens such as necrotrophs.     

小麦条锈菌吸器母细胞超微结构的研究

本文利唱电镜技术研究了小麦条锈菌吸器母细胞的超微特征。观察发现,小麦条锈菌吸器母细胞大部位于胞间菌丝的顶部,但也可形成于两菌丝细胞间,同一菌丝细胞上可着生多个吸器母细胞,吸器母细胞的多核现象较为普遍。吸器母细胞壁由6层组成,而其隔膜可分辩为4层。细泡化学染色结果表明隔膜突中含有多糖类物质,吸器母细胞隔膜突的出现和消失与吸器的发育密切相关。本文结果表明小麦条锈菌吸器母细胞的一些超微特征明显不同于其它锈菌。     

小麦条锈菌吸器母细胞入侵菌丝现象的进一步研究

应用电镜技术对小麦条锈菌吸器母细胞入侵自身菌丝的现象进行了研究,观察发现,在吸器母细胞与寄主细胞和菌丝细胞同时相接触的情况下,入侵栓可在与寄主细胞接触处形成,也可在与菌丝接触处形成;在菌落中心部位,吸器母细胞虽然未与寄主细胞接触,但同样可在与菌丝细胞接触处产生入侵栓;吸器母细胞在与菌丝接触处形成的人侵栓,其超微结构正常,并且可侵入到菌丝细胞壁内,但是未能穿透菌丝细胞壁。本文观察结果表明,小麦条锈菌吸器母细胞和人侵栓形成所需诱导因子可能是物理接触作用,而不涉及到化学作用,并且该病菌与寄主间的识别作用可能发生在入侵栓形成之后。     

Ultrastructure of the Host-Pathogen Relationship in Entomosporium Leaf Spot Disease of Photinia

Entomosporium mespili appears to be a hemibiotroph on infected Photinia leaves. This fungal pathogen produced distinctive haustoria in living host cells in young lesions. Each haustorium possessed a long slender neck with a single septum and an enlarged distal body that contained a single nucleus. A collar of host cell wall material was associated with the haustorial neck. Intact haustoria also were found in necrotic cells of older lesions. However, by this stage of disease development, the pathogen also possessed an extensive system of branched, septate hyphae that grew indiscriminately between and through dead and dying host cells. These hyphae eventually gave rise to a subcutaneous layer of sporogenous cells that formed conidia.     

ELECTRON MICROSCOPY OF THE HOST-PARASITE RELATIONSHIPS IN STEM RUST OF WHEAT

Ehrlich , H. G., and Mary A. Ehrlich . (Duquesne U., Pittsburgh, Pa.) Electron microscopy of the host-parasite relationships in stem rust of wheat.—Amer. Jour. Bot. 50(2): 123–130. Illus. 1963.—A series of micrographs showing intercellular dikaryotic mycelium, haustorial mother cells, stages in haustorial formation, and haustoria within host cells are presented in the present report. Of special interest and potential significance in a study of obligate parasitism is an encapsulation ranging from 800 to 3400 A in thickness which surrounds the haustorium, but which is not present around the intercellular hyphae. The encapsulation completely encases the haustorium proper; it is bounded on the inside by the cell wall of the haustorium, and its thin membranous outer margin abuts directly on the protoplast of the host cell. The nature of the material composing the encapsulation is uncertain, but it appears to originate from the haustorial protoplast, and at least a portion of it may be fungal cytoplasm. This newly described structure represents the actual interface between the host and pathogen. Small vesicles which seem to originate from the outer margin of the encapsulation are sometimes found in the host cytoplasm surrounding apparently vigorous haustoria. The vesicles are bounded by a membrane and contain particulate material.     

THE HOST-PARASITE INTERFACE OF PERONOSPORA MANSHURICA ON GLYCINE MAX

Peyton , G. A., and c. c . Bowen . (Iowa State U., Ames.) The host-parasite interface of Peronospora manshurica on Glycine max. Amer. Jour. Bot. 50(8): 787-797. Illus. 1983.—The fine structure of the vegetative intercellular hyphae, intracellular haustoria, and invaded host cells is described. Perinuclear Golgi apparatus and extensive lomasomes are characteristic of the hyphae and haustoria of this fungus. The invading haustoria do not penetrate the plasma membrane of the host. Except for a sheath near the point of penetration, there is no evidence of true host wall around the haustorium. However, a “zone of apposition,” with staining properties different from those of normal host cell wall, forms around the haustorial wall between the host and parasite plasma membranes. Special modifications of the host cytoplasm in the vicinity of haustoria are described, including formation of “secretory bodies” and their apparent discharge through the host plasma membrane into the zone of apposition. This phenomenon, together with an apparent increase in the number of ribosomes in the host, suggests highly specific reactions of the host cytoplasm to the invading haustorium.     

Ultrastructural specialization at the host-pathogen interface in rust-infected flax

Summary Ultrastructure of the association between the rust fungus, Melampsora lini, and a compatible variety of flax, Linum usitatissimum, was studied to clarify the structural relationships and interactions at the site of host penetration and at the host-parasite interface. Results of freeze-etching as well as a special section-staining procedure consisting of periodate-chromate-phosphotungstate (PACP) are shown with a host-parasite combination for the first time. The host plasma membrane is invaginated by the fungus and forms a continuous boundary around the fungal haustoria which penetrate the host cells. No morphological continuities are observed linking the protoplasts of host and fungus. With both freeze-etching and the PACP stain, the invaginated portion of the host plasma membrane at the host-parasite interface shows distinctive features that are not characteristic of the non-invaginated portion of the membrane. This localized specialization of host plasma membrane in response to the fungus appears as a significant and consistent feature of the host-parasite interaction. The host plasma membrane is separated from the haustorial wall by an amorphous layer of sheath material which covers the body but not the neck of the haustorium. This sheath provides the environment in which the haustorium exists and functions during the course of the host-parasite association. Occasionally, a collar of wall-like material derived from the host cell forms around the haustorial neck. The collar is continuous with the host wall and is distinct and discontinuous from the haustorial sheath. In fewer than 5% of the infected cells this wall material encases entire haustoria. The fungal wall is structurally specialized around the site of host penetration, and it becomes intimately associated with the host wall where the fungus penetrates into the lumen of the host cell. During penetration, the host and fungal walls appear to be fused so that the interface between them is not clearly delineated. The haustorial wall is continuous, via the haustorial neck, with the wall of the haustorial mother cell which lies outside the host cell. Different staining properties reveal this wall continuum to consist of several well-defined regions having different structure or composition. A ring of fungal wall material midway along the haustorial neck stains densely with lead citrate, but is preferentially etched away by periodic acid. The neck ring denotes a transition in the staining reaction of the fungal wall, from that present in the region of host penetration to that of the wall surrounding the haustorium. The findings demonstrate specialization of the fungal wall in the area of host penetration as well as specialization of the host plasma membrane at the host-parasite interface to a degree not previously realized from ultrastructural information.     

种衣剂17号包衣对小麦条锈菌发育影响的超微结构研究

本研究采用电镜技术研究了种衣剂17号对小麦条锈菌发育的影响。观察结果表明,该种衣剂引起病菌和寄主细胞内发生了一系列变化。病菌菌丝和吸器内脂肪粒和液泡明显增加;菌丝壁和吸器壁呈不规则加厚;菌丝分枝处无隔膜产生或隔膜畸形;有的吸器母细胞产生的畸形入侵栓,大都不能穿透寄主细胞壁,初生吸器外间质内沉积有染色较深的物质,次生吸器可产生多个不规则分枝,但不能扩张膨大;菌丝外渗的物质可能引起寄主细胞的坏死;大多数受侵寄主细胞可分泌形成较大的胼胝质,有时寄主细胞分泌的物质可将吸器体完全包围起来。上述结果表明,种衣剂17号不仅可直接作用于条锈菌,而且也可通过影响寄主而间接地影响病菌。     

Ultrastructure of the haustoria or intracellular hyphae in four different fungi

Summary An examination was made of the ultrastructure of haustoria or intracellular hyphae in four fungi: an obligate parasite (Puccinia hordei), a facultative parasite (Exobasidium japonicum) and two facultative saprophytes (Phytophthora palmivora and Sclerotinia fructigena). P. hordei haustoria showed the typical ultrastructure and host-parasite interface of most of the obligate parasites already studied. Connections between the host endoplasmic reticulum and host plasmalemma were observed at the encapsulation site. Tubules connecting the haustorial cytoplasm with the encapsulation, through the haustorial wall were occasionally seen. The host cell remained alive in the presence of the parasite. E. japonicum haustoria lacked a neck and encapsulation and were irregularly shaped, with branches which appeared to be partly surrounded by a sheath. Some of these branches showed cytoplasmic connections between the parasite and the host through the sheath. All the observed haustoria of E. japonicum were anucleate and contained only a few mitochondria and sparse membranes. The host cell was dead and its organelles disorganized. P. palmivora haustoria were simple with nucleus, endoplasmic reticulum, mitochondria and Golgi bodies. Neither sheath nor encapsulation was observed, and the host cell was also dead and disorganized. S. fructigena did not produce haustoria of any kind, the intercellular hyphae became intracellular by the degradation of the host cell walls, and the host cells were killed in advance of the growing hyphae.It is suggested that a new definition of haustorium is required to include all these intermediate haustorial bodies which cannot be included within the present concept of haustorium.     

马铃薯对晚疫病水平抗性的组织细胞学观察

以马铃薯晚疫病水平抗性品种LBr-12和感病品种费乌瑞它为材料,采用普通光学和电子显微镜技术,系统研究了马铃薯与晚疫病菌(致病疫霉)互作的组织细胞学反应特征。观察结果显示:(1)接种后,水平抗性材料LBr-12出现过敏反应,病菌被限制在侵染点的几个细胞中,菌丝产生较少的分支和吸器。(2)感病品种费乌瑞它被侵染细胞呈蔓延趋势,菌丝产生较多的分支和吸器。(3)电镜观察发现,抗病品种上病菌的胞间菌丝、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,包括原生质的电子致密度加深、液泡增多变大、菌丝细胞壁不规则增厚、细胞器排列紊乱及解体、吸器母细胞及吸器形态异常、病菌最终畸形坏死,同时发现抗病品种受病菌侵染时可迅速产生结构防卫反应,形成的细胞壁沉积物使胞壁极度增厚或细胞膜上产生乳突状结构。     

Observations on the ultrastructure of the uredinial stage ofPuccinia polypogonis onPolypogon monspeliensis

The ultrastructure of the uredinial stage of the rust fungus,Puccinia polypogonis onPolypogon monspeliensis is described, using scanning and transmission electron microscopy. This study examined the urediniospores, intercellular hyphae, and haustoria of the fungus. The formation and structure of urediniospores is similar to those of otherPuccinia species. The ultrastructure of intercellular hyphae and haustoria is similar to those of other rust fungi, but with some differences. No modifications are observed in the wall of the haustorial mother cells during penetration. A collar is found only around old haustoria. In most cases, one nucleus is detected inside the haustorial body and no nucleoli are seen in the nuclei of intercellular hyphae and haustoria. The host-parasite interface, including extrahaustorial matrix and extrahaustorial membrane, is also discussed and compared with those of other rust fungi.     

小麦条锈菌吸器超微结构和细胞化学的研究

本文应用电镜技术和细胞化学方法,对小麦条锈菌吸器和入侵点的超微结构进行了研究。小麦条锈菌吸器由呈管状的颈部和顶端膨大的吸器体组成,颈部壁和吸器体壁相互连贯,均为两层,并且含有多糖物质。在颈部中段存在有一染色较深的颈环结构。观察发现吸器中的多核现象极为普遍。细胞化学染色结果表明:在吸器外间质内分布有多糖物质;经蛋白消酶解处理后,吸器外间质中可观察到染色较深的纤丝状物质。在入侵点部位,吸器母细胞壁因局部增厚而呈凸镜状,入侵栓壁由内、外两层构成,这两层分别与吸器母细胞壁的第六层和第五层相连接。本研究还观察到同一入侵点产生两个入侵栓的现象。     

抗病品种中小麦条锈菌细胞的超微结构变化过程

本文就寄主抗病性表达过程中,小麦条锈菌细胞的超微结构变化进行了系统地观察研究。结果表明:胞间菌丝的细胞壁染色逐渐加深,厚度加宽,结构疏松,形成小空洞,并逐渐解体;细胞质逐渐凝聚、脂肪粒的数量增多、有黑色颗粒状沉积物积累;细胞质中小囊泡数目增多并逐渐融合成大液泡,线粒体数目增多,并逐渐肿胀和解体。次生吸器畸形,初生吸器体呈圆球形。吸器壁加厚,染色加深;在吸器的中央,细胞质逐渐分解而形成空泡;线粒体数目增多,并逐渐肿胀和解体;吸器外质膜呈皱褶状,吸器外间质加宽,其中有大量的丝状或颗粒状内含物形成;吸器形态结构的变化均早于其胞间菌丝。     

Structure and Development of the Mature Secondary Haustorium in Alectra vogelii Benth

Anatomical investigations were carried out on the structureand development of the mature secondary haustorium in Alectravogelii growing on Arachis hypogaea or Vigna unguiculata. Followingthe formation of the young secondary haustorium, both the cambiumand pericycle of the host root directly opposite the young secondaryhaustorium are stimulated to divide and form new tissues andorgans including haustorial roots. Further proliferations ofthe host root pericycle and the haustorial cortex give riseto a large, tuberous and complex mature secondary haustoriumwithin which the tissues of the host and parasite remain inintimate contact forming a perfect graft union with a wide zoneof contact. Apart from the haustorial axial xylcm strand whichnormally connects the xylem of the parasite secondary root withthat of the host, direct xylary connections are also establishedbetween the axial xylem of the haustorium and the xylem of thehaustorial roots. The entire surface of the mature secondaryhaustorium of Alectrais covered with these haustorial rootsas was previously observed in its mature primary haustorium. Alectra vogelii Benth, secondary haustorium, haustorium, haustorial roots, root parasite, hemiparasitism, Arachis hypogaea, Vigna unguiculata     

Comparative ultrastructure of aecial and telial infections of the autoecious rust fungus Puccinia tuyutensis

This study demonstrates morphological differences between aecial and telial stages of the autoecious rust Puccinia tuyutensis. The aeciospores possess verrucose ornamentation while the teliospores have smooth surfaces. The aecial and telial haustoria of this rust produced in the mesophyll of Cressa cretica differ morphologically in the following respects:(1) the haustorial mother cell of telial haustorium is more differentiated than that of aecial haustorium and its wall at the penetration site is composed of 4 layers; (2) the aecial haustorium is filamentous in appearance and slightly constricted at the point of entry into the host cell, while the telial haustorium is clavate and possesses a narrow neck with a densely staining neckband and swollen body; (3) the neck of the telial haustorium is always associated with numerous vesicles while that of the aecial haustorium is not. Vascular tissue of host leaves is heavily invaded by aecial haustoria but not by telial haustoria.     

Structure and development of the upper haustorium in the parasitic flowering plant Cuscuta japonica (Convolvulaceae)

The anatomical and ultrastructural development of the haustorium of the Cuscuta japonica, a holoparasitic angiosperm, growing on the host plant Impatiens balsamina was studied. After the shoot tips of light-grown parasite seedlings contacted the host, the upper haustorium (external to the host organ) developed through three main successive stages of the haustorial initials, the meristem, and the endophyte primoridium (EP) within the middle layer of the cortex of the parasite stem. The haustorial initial cells were characterized by abundant starch-bearing amyloplasts and mitochondria with an expanded intermembrane space. The meristem cells had numerous large chloroplasts with well-developed thylakoids, reflecting the capability for photosynthesis. Commonly, all three stages of haustorial cells contained conspicuous, large nuclei with enlarged nucleoli and dense cytoplasm including many other organelles, indicating a very active metabolism. In the final stage of upper haustorium development, the meristem cells differentiated into the EP, a host-penetrating tissue. The primordium had smaller file cells at the proximal end and elongate digitate cells at the distal end. The file cells divided actively, while the digitate cells contained abundant chloroplasts, dictyosomes, rough endoplasmic reticulum, and other organelles, suggesting that the EP was cytohistologically well organized for penetration into the host tissue.