scholarly journals Differentiation of aecidiospore- and uredospore-derived infection structures on cowpea leaves and on artificial surfaces by Uromyces vignae

1993 ◽  
Vol 71 (9) ◽  
pp. 1236-1242 ◽  
Author(s):  
M. Stark-Urnau ◽  
K. Mendgen
Keyword(s):  
Key Words ◽  
Mother Cell ◽  
Host Plants ◽  
Rust Fungus ◽  
Host Cells ◽  
In Planta ◽  
Infection Structures ◽  
Artificial Surfaces ◽  
Uromyces Vignae ◽  
Mother Cells

Aecidiospores and uredospores are the two dikaryotic spore forms of the cowpea rust fungus Uromyces vignae. After germination they can be induced to develop a series of infection structures including appressoria, infection hyphae, and haustorial mother cells. Haustoria are then formed within host cells. The differentiation of infection structures was compared on polystyrene membranes with defined topographies, on scratched polyethylene membranes, and in planta. On polystyrene membranes with defined topographies both sporelings showed highest rates of differentiation on ridges 0.3 μm high but aecidiosporelings responded less efficiently to this stimulus than uredosporelings. On scratched polyethylene membranes, almost 90% of both sporelings differentiated appressoria, but only 10% formed haustorial mother cells; haustoria were not observed. On the host plant, by contrast, only 50% of the sporelings differentiated appressoria, but most of these formed haustorial mother cells and haustoria. In planta haustorial mother cell development occurred approximately 6 h earlier than on inductive membranes. Infection structures formed on artificial membranes and on host plants were similar in morphology and nuclear condition. Key words: cowpea rust fungus, nucleus, appressorium.

Haustorial mother cell development by Uromyces vignae on collodion membranes

1988 ◽  
Vol 66 (4) ◽  
pp. 736-741 ◽  
Author(s):  
Michèle C. Heath ◽  
C. J. Perumalla
Keyword(s):  
Cell Wall ◽  
Mother Cell ◽  
Rust Fungus ◽  
Potential Binding ◽  
Disulphonic Acid ◽  
Uromyces Vignae ◽  
Mother Cells ◽  
Chloroform Methanol ◽  
Infection Hypha ◽  
Mother Cell Wall

The development of infection structures by the rust fungus Uromyces vignae was observed on oil-containing collodion membranes. About 40% of infection hyphae formed a haustorial mother cell, but this structure commonly senesced and died more rapidly than the infection hypha to which it was attached. These data suggest that the continued development of the haustorial mother cell requires some component normally provided by the host plant. Before they died, many haustorial mother cells apparently formed the thickened region of the wall which normally is traversed by the penetration peg during haustorium formation. Such a peg was observed in the centre of up to 40% of these thickened regions. However, no pegs protruded beyond the haustorial mother cell far enough to be called a haustorial neck. The thickened region of the haustorial mother cell wall could be differentiated from the rest of the wall by its lack of fluorescence under ultraviolet irradiation when mounted in Calcofluor or SITS (4-acetomido-4′-iso-thiocyanatostilbene-2,2′-disulphonic acid). Treatment with alkali, acid, chloroform–methanol, protease, and laminarinase did not affect this differential fluorescence, and the haustorial mother cell wall stained uniformly for proteins, carbohydrates, and chitin. Since Calcofluor normally binds to chitin, these data suggest that the thickened region of the haustorial mother cell wall may physically exclude the dye or may contain potential binding sites that are masked by other wall components.

scholarly journals Candidate Effector Proteins of the Rust Pathogen Melampsora larici-populina Target Diverse Plant Cell Compartments

2015 ◽  
Vol 28 (6) ◽  
pp. 689-700 ◽  
Author(s):  
Benjamin Petre ◽  
Diane G. O. Saunders ◽  
Jan Sklenar ◽  
Cécile Lorrain ◽  
Joe Win ◽  
...  
Keyword(s):  
Rust Fungus ◽  
Effector Proteins ◽  
Host Cells ◽  
Plant Proteins ◽  
In Planta ◽  
Biologically Relevant ◽  
Heterologous System ◽  
Biotrophic Pathogens ◽  
Small Set ◽  
Clone And Express

Rust fungi are devastating crop pathogens that deliver effector proteins into infected tissues to modulate plant functions and promote parasitic growth. The genome of the poplar leaf rust fungus Melampsora larici-populina revealed a large catalog of secreted proteins, some of which have been considered candidate effectors. Unraveling how these proteins function in host cells is a key to understanding pathogenicity mechanisms and developing resistant plants. In this study, we used an effectoromics pipeline to select, clone, and express 20 candidate effectors in Nicotiana benthamiana leaf cells to determine their subcellular localization and identify the plant proteins they interact with. Confocal microscopy revealed that six candidate effectors target the nucleus, nucleoli, chloroplasts, mitochondria, and discrete cellular bodies. We also used coimmunoprecipitation (coIP) and mass spectrometry to identify 606 N. benthamiana proteins that associate with the candidate effectors. Five candidate effectors specifically associated with a small set of plant proteins that may represent biologically relevant interactors. We confirmed the interaction between the candidate effector MLP124017 and TOPLESS-related protein 4 from poplar by in planta coIP. Altogether, our data enable us to validate effector proteins from M. larici-populina and reveal that these proteins may target multiple compartments and processes in plant cells. It also shows that N. benthamiana can be a powerful heterologous system to study effectors of obligate biotrophic pathogens.

The temporal relationship between the development of intracellular hyphae and haustoria by Physopella zeae in Zea mays

1988 ◽  
Vol 66 (4) ◽  
pp. 742-744 ◽  
Author(s):  
Michèle C. Heath ◽  
M. R. Bonde
Keyword(s):  
Plant Cell ◽  
Mother Cell ◽  
Plant Cell Wall ◽  
Rust Fungus ◽  
Morphological Differentiation ◽  
Adjacent Cell ◽  
Previous Suggestion ◽  
Epidermal Tissue ◽  
Developmental Relationship ◽  
Mother Cells

To investigate the developmental relationship between haustoria and intracellular hyphae, fixed and cleared whole mounts of com leaves infected with the tropical corn rust fungus Physopella zeae (Mains) Cumm. & Ramachar were examined by interference contrast light microscopy. Haustoria were clearly distinguished from intracellular hyphae by their morphological differentiation into a filamentous body and a narrow neck. The latter was encircled by a thin neckband, which appeared to develop in young haustoria at the time when the haustorial body started to expand. Observations made at the colony margins suggested that the fungus grew into uninvaded epidermal tissue in the following sequence: (i) formation of a haustorium from a haustorial mother cell in an adjacent cell, (ii) formation of an intracellular hypha next to the haustorium by the same intracellular hypha that had formed the haustorial mother cell, (iii) growth of the intracellular hypha within the newly invaded plant cell, (iv) formation by the intracellular hyphae of haustorial mother cells against the plant cell wall adjacent to an uninvaded cell, and (v) formation of haustoria in the uninvaded cell. These results support the previous suggestion that the haustorium may induce a state of susceptibility in the plant cell, "paving the way" for invasion by the intracellular hyphae.

Ultrastructure of the early stages of infection of peanut leaves by the rust fungus Puccinia arachidis

1989 ◽  
Vol 67 (12) ◽  
pp. 3570-3579 ◽  
Author(s):  
C. W. Mims ◽  
J. Taylor ◽  
E. A. Richardson
Keyword(s):  
Host Cell ◽  
Mother Cell ◽  
Primary Infection ◽  
Rust Fungus ◽  
Mitotic Division ◽  
Infection Process ◽  
Rust Disease ◽  
Puccinia Arachidis ◽  
Mother Cells ◽  
Infection Hypha

Peanut rust disease proved to be an excellent system for ultrastructural study of development of infection structures by the fungus Puccinia arachidis. Fungal structures were clearly visible by light microscopy in fixed and embedded samples and could be located either on leaf surfaces or within the large substomatal chambers of peanut leaves. Samples could easily be oriented for thin sectioning. The infection process was a highly orchestrated process involving precisely timed events and highly specialized structures. Infection pegs developed from appressoria over stomata and entered the leaf by growing into the openings between guard cells. Once past the rim formed by the guard cell walls, the infection peg expanded to form a substomatal vesicle in which a synchronous mitotic division of the four nuclei occurred. A primary infection hypha then developed from the vesicle and grew into the mesophyll of the leaf until its tip or side contacted a host cell. A septum then delimited a binucleate or trinucleate terminal haustorial mother cell from the remainder of the infection hypha. The wall of the haustorial mother cell became closely appressed to that of the host cell. Following differentiation of the haustorial mother cell, a penetration peg arose from it and penetrated the host cell wall. The peg invaginated the host cell plasma membrane as it elongated and then expanded at its tip to form the haustorium body into which most of the contents of the haustorial mother cell moved. Meanwhile, the primary infection hypha formed secondary hyphae that gave rise to additional haustorial mother cells and haustoria. Key words: Puccinia arachidis, peanut rust, infection process, ultrastructure.

scholarly journals Characterization of In Planta—Induced Rust Genes Isolated from a Haustorium-Specific cDNA Library

1997 ◽  
Vol 10 (4) ◽  
pp. 427-437 ◽  
Author(s):  
Matthias Hahn ◽  
Kurt Mendgen
Keyword(s):  
Cdna Library ◽  
Expression Patterns ◽  
Host Cells ◽  
In Planta ◽  
Developmentally Regulated ◽  
Uromyces Fabae ◽  
Infection Structures ◽  
Genes Encoding ◽  
Peptidyl Prolyl Isomerases

Rust fungi are plant parasites that depend on living host tissue for growth. For invasion of leaves, dikaryotic urediospores differentiate germ tubes and infection structures that penetrate through stomata. Biotrophic growth occurs by intercellular mycelia that form haustoria within host cells. A cDNA library was constructed from haustoria isolated from broad bean leaves infected by Uromyces fabae. Differential screening revealed that a high proportion (19%) of the haustorial cDNAs are specifically expressed in planta but are not expressed, or are much weaker, in germlings or infection structures produced in vitro. A total of 31 different in planta-induced genes (PIGs) were identified. Some of the PIGs are highly expressed in haustoria. The PIGs are single or low copy number genes in the rust genome. A variety of developmentally regulated expression patterns of PIG mRNAs were observed. Sequence analysis of PIG cDNAs revealed similarities to genes encoding proteins involved in amino acid transport, thiamine biosynthesis, short-chain dehy-drogenases, metallothioneins, cytochrome P-450 monooxy-genases, and peptidyl-prolyl isomerases.

Structural studies of the development of infection structures of cowpea rust, Uromyces phaseoli var. vignae. I. Nucleoli and nuclei

1978 ◽  
Vol 56 (6) ◽  
pp. 648-661 ◽  
Author(s):  
Michèle C. Heath ◽  
I. Brent Heath
Keyword(s):  
Mother Cell ◽  
Cell Formation ◽  
Structural Studies ◽  
Nucleolar Activity ◽  
Infection Structures ◽  
Uromyces Phaseoli ◽  
Living Material ◽  
Mother Cells ◽  
Germ Tubes ◽  
Infection Hypha

Light microscopical observations of living germ tubes and infection structures of cowpea rust were combined with an ultrastructural study to show that a nucleolus was present in the interphase nucleus at all stages of development from uredospore germination through to new uredospore formation. Vacuolate nucleoli were common in germ tubes but only nonvacuolate nucleoli were observed at other stages of fungal development. When grown on oil-containing collodion membranes, germinating uredospores, germ tubes, appressoria, and infection hyphae without haustorial mother cells all contained nucleoli composed primarily of nongranular material. Predominantly granular nucleoli were observed in developing uredospores and all parasitic stages in the leaf after the formation of the first haustorial mother cell. However, the fact that granular nucleoli were also seen in a membrane-grown infection hypha after haustorial mother cell formation suggested that the host was not required to stimulate the resumption of nucleolar activity. Electron-opaque patches, presumed to be condensed chromatin, were most prominent in the nucleoplasm of haustorial mother cells and virtually absent in germinating uredospores and germ tubes. The significance of this observation is discussed. A reduction in nuclear volume was observed in living material prior to cytokinesis in the appressorium and the substomatal vesicle. Evidence suggested that this reduction was produced by the expulsion of part of the nucleoplasm, plus the nucleolus, during mitosis rather than before as suggested for other rusts. Nuclei of haustorial mother cells and haustoria were also smaller than those in intercellular hyphae but the mechanism by which this was achieved could not be determined.

Fungal development and host cell responses to the rust fungus Puccinia substriata var. indica in seedling and mature leaves of susceptible and resistant pearl millet

1991 ◽  
Vol 69 (6) ◽  
pp. 1207-1219 ◽  
Author(s):  
J. Taylor ◽  
C. W. Mims
Keyword(s):  
Host Cell ◽  
Pearl Millet ◽  
Rust Fungus ◽  
Plant Cells ◽  
Host Cells ◽  
Resistant Cultivar ◽  
Fungal Colonization ◽  
Mature Leaves ◽  
Before And After ◽  
Mother Cells

The rust fungus Puccinia substriata var. indica established a compatible relationship with host cells, characterized by large numbers of haustoria and an extensive system of intercellular hyphae, in seedling leaves of the susceptible pearl millet cultivar Tift 23DB. At some infection sites, however, necrotic host cells and papillae formed by plant cells adjacent to infection hyphae or haustorial mother cells were noted. In seedling leaves of the moderately resistant cultivar 86-8770, the initial interaction between host cells and the pathogen was quite variable and included successful haustorium formation as well as papilla deposition. Necrosis of host cells apparently developed as a gradual disorganization of the cytoplasm of invaded and surrounding host cells and occurred at all infection sites by 2 days postinoculation. In seedling leaves of the highly resistant cultivar Tift 85DB, haustoria were established at early stages of development, followed by a rapid necrosis response at 1 day postinoculation. Host cell disintegration was noted both before and after abnormalities in haustoria were observed. In mature leaves of all three cultivars, wall deposits were quite extensive at 12 h postinoculation. In addition, necrotic plant cells appeared rapidly in both susceptible and resistant cultivars. Both of these factors may have contributed to the increased resistance to fungal colonization observed in mature leaves. Key words: Puccinia substriata var. indica, pearl millet rust, host resistance, ultrastructure.

scholarly journals Early events in living epidermal cells of cowpea and broad bean during infection with basidiospores of the cowpea rust fungus

1991 ◽  
Vol 69 (10) ◽  
pp. 2279-2285 ◽  
Author(s):  
Haixin Xu ◽  
Kurt Mendgen
Keyword(s):  
Vicia Faba ◽  
Broad Bean ◽  
Rust Fungus ◽  
Infection Process ◽  
Host Cells ◽  
Appressorium Formation ◽  
Vigna Sinensis ◽  
Infected Cells ◽  
Uromyces Vignae ◽  
Defence Reactions

The infection process of basidiospores of the cowpea rust fungus (Uromyces vignae) was studied on living host (Vigna sinensis) and nonhost (Vicia faba) leaves using light microscopy with differential interference contrast optics. During the first 8 h, fungal development was similar on host and on nonhost leaves. Penetration and production of intraepidermal vesicles occurred in nonhost cells 4 h earlier than in host cells. Penetration frequency was also higher in nonhost leaves. These results suggest that the cuticle of the cowpea plant delays basidiospore infection. Both host and nonhost cells produced cytoplasmic aggregates during appressorium formation and again, a few hours later, during penetration of the epidermal cell wall. Cytoplasmic aggregates were also observed in cells adjacent to a collapsing cell. Papillae were observed at most infection sites in both host and nonhost cells. The nuclei of infected cells migrated towards the penetration site in both plant–pathogen combinations. Nuclear size increased considerably only in the nonhost epidermis and decreased again markedly after cell collapse. In the nonhost cells, three types of defence reactions occurred during or after formation of the intraepidermal vesicle. First, following the halt of cytoplasmic streaming, the cytoplasm of the invaded cell either contracted or disintegrated into granules. Alternatively, the cytoplasm continued streaming but darkly pigmented material encased the fungal infection structure. Key words: basidiospore, broad bean (Vicia faba), cowpea (Vigna sinensis), cowpea rust fungus (Uromyces vignae), hypersensitivity, nonhost resistance.

Effects of the Srl5 allele for resistance on development of the stem rust fungus and cellular responses in wheat

1986 ◽  
Vol 64 (3) ◽  
pp. 626-631 ◽  
Author(s):  
H. D. M. Gousseau ◽  
B. J. Deverall
Keyword(s):  
Stem Rust ◽  
Rust Fungus ◽  
Cell Formation ◽  
Cellular Responses ◽  
Host Cells ◽  
Puccinia Graminis ◽  
Wheat Line ◽  
Cell Necrosis ◽  
Virulent Strains ◽  
Mother Cells

The development of avirulent and virulent strains of stem rust (Puccinia graminis Pers. f.sp. tritici Eriks. & Henn.) in a susceptible wheat line and two cultivars bearing the Sr15 allele for resistance was studied, mainly by fluorescence microscopy. Formation of appressoria, substomatal vesicles, infection hyphae, and the first haustorium was unaffected by resistance. The first effect of Sr15 expression was a slower rate of haustorial mother cell formation and was first seen 48 h after inoculation. Effects on hyphal branching and colony radii followed. Necrosis of host cells was first seen at 42 h, but inspection of individual infection sites showed that necrosis did not coincide with effects on haustorial mother cells. It is possible that deterioration of host cells leading to visible host cell necrosis may be related to effects on rust development. Sr15 expression gave a mesothetic reaction, first seen microscopically 60 h after inoculation. Differences between individual infection sites in this reaction may be related to the timing of the onset of necrosis.

In vitro formation of haustoria of the cowpea rust fungus Uromyces vignae in the absence of a living plant cell. II. Electron microscopy

1990 ◽  
Vol 68 (2) ◽  
pp. 278-287 ◽  
Author(s):  
Michèle C. Heath
Keyword(s):  
Plant Cell ◽  
Rust Fungus ◽  
Periodic Acid ◽  
Outer Wall ◽  
Wall Layer ◽  
Living Plant ◽  
Uromyces Vignae ◽  
Mother Cells ◽  
Extrahaustorial Matrix

The ultrastructure of infection hyphae, haustorial mother cells, and haustoria of Uromyces vignae formed on collodion membranes is described after conventional preparation and after treatment with periodic acid – thiocarbonhydrazide – silver proteinate or periodic acid – chromic acid – phosphotungstic acid treatments. Infection hyphae and haustorial mother cells developed normally in vitro but lacked an outer wall layer present in older infections in the host plant. Haustorium formation in vitro was accompanied by the development of elaborations of the plasmalemma along the infection hypha side of the haustorial mother cell septum, but their contents did not show identical staining responses to the haustorial neck wall as reported for other rust fungus species. Haustorial necks, and to a lesser extent haustorial bodies, were coated with a fibrillar material, the staining characteristics of which were similar to material normally considered part of the extrahaustorial matrix in infected plants. The restriction of this material to the haustorium suggests that it may play an important role in the interaction between the haustorium and the plant cell.

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