Conidial anastomosis tubes in Colletotrichum

Roca, M. Gabriela; Davide, Lisete Chamma; Mendes-Costa, Maria Cristina; Wheals, Alan E.

doi:10.1016/s1087-1845(03)00088-4

Cited by 87 publications

(107 citation statements)

References 24 publications

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“…Conidial anastomosis tubes were previously reported in leaf pathogens such as Colletotrichum spp. (41). Here we observed frequent anastomosis events during the growth of F. oxysporum on tomato roots and found that strains impaired in VHF were reduced in root adhesion and colonization efficiency.…”

mentioning

confidence: 67%

Vegetative Hyphal Fusion Is Not Essential for Plant Infection by Fusarium oxysporum

Prados-Rosales

Pietro

2008

Eukaryot Cell

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Vegetative hyphal fusion (VHF) is a ubiquitous phenomenon in filamentous fungi whose biological role is poorly understood. In Neurospora crassa, the mitogen-activated protein kinase (MAPK) Mak-2 and the WW domain protein So are required for efficient VHF. A MAPK orthologous to Mak-2, Fmk1, was previously shown to be essential for root penetration and pathogenicity of the vascular wilt fungus Fusarium oxysporum. Here we took a genetic approach to test two hypotheses, that (i) VHF and plant infection have signaling mechanisms in common and (ii) VHF is required for efficient plant infection. F. oxysporum mutants lacking either Fmk1 or Fso1, an orthologue of N. crassa So, were impaired in the fusion of vegetative hyphae and microconidial germ tubes. ⌬fmk1 ⌬fso1 double mutants exhibited a more severe fusion phenotype than either single mutant, indicating that the two components function in distinct pathways. Both ⌬fso1 and ⌬fmk1 strains were impaired in the formation of hyphal networks on the root surface, a process associated with extensive VHF. The ⌬fso1 mutants exhibited slightly reduced virulence in tomato fruit infection assays but, in contrast to ⌬fmk1 strains, were still able to perform functions associated with invasive growth, such as secretion of pectinolytic enzymes or penetration of cellophane sheets, and to infect tomato plants. Thus, although VHF per se is not essential for plant infection, both processes have some signaling components in common, suggesting an evolutionary relationship between the underlying cellular mechanisms.The ability of filamentous fungi to form multicellular colonies can be regarded as the result of two distinct morphogenetic processes, (i) growth of individual hyphae by tip extension and branching, which requires maintenance of cell polarity and redirection of the growth axis in response to environmental cues (30), and (ii) establishment of an interconnected hyphal network or mycelium through fusion of individual hyphae. The latter process is known as vegetative hyphal fusion (VHF) or anastomosis (2) and appears to be ubiquitous in filamentous fungi, yet its biological function is unknown. Suggested roles which remain to be tested experimentally include general homeostasis, translocation of nutrients and water, and intrahyphal communication within the fungal colony (17, 37).Evidence from genetic studies in the model ascomycete Neurospora crassa support the notion that VHF is a highly complex and regulated developmental process (14-16). A number of genes required for VHF have recently been identified in N. crassa, including ham-2, which encodes a putative transmembrane protein (47), and so, which encodes a polypeptide with a WW protein-protein interaction domain (12). Besides these genes with hitherto unknown functions, components of a highly conserved mitogen-activated protein kinase (MAPK) cascade, orthologous to the Saccharomyces cerevisiae Fus3 mating pathway, are also required for VHF (16). Mutants of N. crassa lacking the MAPK Mak-2 or the MAPK kinase kinase Nrc-1 (33), as ...

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confidence: 67%

Vegetative Hyphal Fusion Is Not Essential for Plant Infection by Fusarium oxysporum

Prados-Rosales

Pietro

2008

Eukaryot Cell

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“…Altogether, these data suggest that different cell fusion regulatory pathways may be involved in vegetative fusion versus trichogyne-conidium and crozier fusion during sexual development. Although the morphology of hyphal and germling fusions in filamentous ascomycete species has been subject to a number of studies (4,20,28,29,39,47,48), the function of the interconnected hyphal colony during fungal developmental processes or growth is only poorly understood. so and the other known fusion mutants of N. crassa exhibit pleiotropic phenotypes (30,39,62).…”

Section: Discussionmentioning

confidence: 99%

“…Germinating conidia can produce specialized hyphae called conidial anastomosis tubes (CATs), which fuse with each other (29,47,48) to establish a hyphal network that rapidly develops into a colony. Fusion events are also required during sexual reproduction in many filamentous ascomycete species.…”

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confidence: 99%

The so Locus Is Required for Vegetative Cell Fusion and Postfertilization Events in Neurospora crassa

et al. 2005

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The process of cell fusion is a basic developmental feature found in most eukaryotic organisms. In filamentous fungi, cell fusion events play an important role during both vegetative growth and sexual reproduction. We employ the model organism Neurospora crassa to dissect the mechanisms of cell fusion and cell-cell communication involved in fusion processes. In this study, we characterized a mutant with a mutation in the gene so, which exhibits defects in cell fusion. The so mutant has a pleiotropic phenotype, including shortened aerial hyphae, an altered conidiation pattern, and female sterility. Using light microscopy and heterokaryon tests, the so mutant was shown to possess defects in germling and hyphal fusion. Although so produces conidial anastomosis tubes, so germlings did not home toward wild-type germlings nor were wild-type germlings attracted to so germlings. We employed a trichogyne attraction and fusion assay to determine whether the female sterility of the so mutant is caused by impaired communication or fusion failure between mating partners. so showed no defects in attraction or fusion between mating partners, indicating that so is specific for vegetative hyphal fusion and/or associated communication events. The so gene encodes a protein of unknown function, but which contains a WW domain; WW domains are predicted to be involved in protein-protein interactions. Database searches showed that so was conserved in the genomes of filamentous ascomycete fungi but was absent in ascomycete yeast and basidiomycete species.

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“…They showed that the CATs in this species were responsible for fusion between conidia in asexual fruit bodies and that nuclei and organelles moved from one conidium to another through fused CATs. A review of the literature revealed that fusion between spore germlings is common, and over 20 species were found to produce structures similar to CATs (35,36). Köhler (24) first showed fusion between germlings of Neurospora spp.…”

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Cell Biology of Conidial Anastomosis Tubes in Neurospora crassa

Arlt²,

et al. 2005

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Although hyphal fusion has been well documented in mature colonies of filamentous fungi, it has been little studied during colony establishment. Here we show that specialized hyphae, called conidial anastomosis tubes (CATs), are produced by all types of conidia and by conidial germ tubes of Neurospora crassa. The CAT is shown to be a cellular element that is morphologically and physiologically distinct from a germ tube and under separate genetic control. In contrast to germ tubes, CATs are thinner, shorter, lack branches, exhibit determinate growth, and home toward each other. Evidence for an extracellular CAT inducer derived from conidia was obtained because CAT formation was reduced at low conidial concentrations. A cr-1 mutant lacking cyclic AMP (cAMP) produced CATs, indicating that the inducer is not cAMP. Evidence that the transduction of the CAT inducer signal involves a putative transmembrane protein (HAM-2) and the MAK-2 and NRC-1 proteins of a mitogen-activated protein kinase signaling pathway was obtained because ham-2, mak-2, and nrc-1 mutants lacked CATs. Optical tweezers were used in a novel experimental assay to micromanipulate whole conidia and germlings to analyze chemoattraction between CATs during homing. Strains of the same and opposite mating type were shown to home toward each other. The cr-1 mutant also underwent normal homing, indicating that cAMP is not the chemoattractant. ham-2, mak-2, and nrc-1 macroconidia did not attract CATs of the wild type. Fusion between CATs of opposite mating types was partially inhibited, providing evidence of non-self-recognition prior to fusion. Microtubules and nuclei passed through fused CATs.Hyphal fusion (anastomosis) is commonly undergone at two stages during the development of the vegetative colony of a filamentous fungus. It occurs initially between spores or spore germlings during the early stages of colony establishment and subsequently between hyphae located behind leading hyphae of the peripheral growth zone of the mycelium. Among other proposed roles, vegetative hyphal fusion is believed to facilitate communication and the transport of water and nutrients within the colony by producing a complex interconnected hyphal network (14).Neurospora crassa is proving to be an excellent model system in which to analyze vegetative hyphal fusion (12,14). Live-cell analysis of hyphal fusion in mature colonies of N. crassa demonstrated that specialized fusion hyphae exhibit positive tropisms by growing (homing) toward each other, and their close vicinity to other hyphae can induce the formation of further fusion hyphae (15). Different stages in the homing and fusion process were defined, and this has been summarized by Glass et al. (14). The nature of the diffusible chemoattractant molecules responsible for these tropisms is unknown (15). A number of mutants unable to undergo hyphal fusion have been isolated. Mutants disrupted in the mak-2 and nrc-1 genes encode a mitogen-activated protein (MAP) kinase and a MAP kinase kinase kinase, respectively. These prote...

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Conidial anastomosis tubes in Colletotrichum

Cited by 87 publications

References 24 publications

Vegetative Hyphal Fusion Is Not Essential for Plant Infection by Fusarium oxysporum

Vegetative Hyphal Fusion Is Not Essential for Plant Infection by Fusarium oxysporum

The so Locus Is Required for Vegetative Cell Fusion and Postfertilization Events in Neurospora crassa

Cell Biology of Conidial Anastomosis Tubes in Neurospora crassa

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