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. 2010 Sep;156(Pt 9):2621-2629.
doi: 10.1099/mic.0.040147-0. Epub 2010 Jun 3.

The ham-5, rcm-1 and rco-1 genes regulate hyphal fusion in Neurospora crassa

Mash'el Salman Aldabbous  1 , M Gabriela Roca  2 , Angela Stout  1 , I-Ching Huang  2 , Nick D Read  2 , Stephen J Free  1
Affiliations

The ham-5, rcm-1 and rco-1 genes regulate hyphal fusion in Neurospora crassa

Mash'el Salman Aldabbous et al. Microbiology (Reading). 2010 Sep.

Abstract

Mutants of Neurospora crassa unable to participate in vegetative hyphal fusion (anastomosis) were isolated and characterized. From this analysis, three genes, rcm-1, rco-1 and ham-5, were identified and shown to be required for hyphal fusion. The rcm-1 and rco-1 genes are homologues of the Saccharomyces cerevisiae SSN6 and TUP1 genes, which encode a dimeric transcription factor in yeast. We demonstrate that in N. crassa the rcm-1 and rco-1 genes are required for hyphal fusion and normal hyphal morphology, and influence both asexual and sexual development. The ham-5 gene encodes a 1686 amino acid protein with two putative WD40 domains, which might participate in protein-protein interactions. ham-5 deletion mutants had a reduced rate of hyphal extension and altered hyphal morphology, and were unable to produce the conidial anastomosis tubes that are required for hyphal fusion during colony initiation.

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Figures

Fig. 1.
Fig. 1.
DIC image of two connected fusion hyphae through which cytoplasm is flowing. These fused hyphae were imaged while sandwiched between two layers of cellophane. Bar, 10 μm.
Fig. 2.
Fig. 2.
Low-temperature scanning electron microscopy of germinating conidia of the wild-type (WT) and ham-5 mutant (MSA-128), showing that the mutant is unable to produce conidial anastomosis tubes (indicated by arrows for the wild-type). Bars, 10 μm.
Fig. 3.
Fig. 3.
Morphology of the wild-type (WT) and hyphal fusion mutants showing growing hyphal tips at the colony periphery, growth on agar plates, and growth on agar slants. Photographs from the MSA-128 (ham-5), PB-S8 (rcm-1), and rco-1rip mutants are shown. Note that the mutant isolates produce conidia over the entire slant while the wild-type produces conidia in abundance at the top of the slant.
Fig. 4.
Fig. 4.
Western blot analysis of MAK-1 and MAK-2 phosphorylated activation sites in the ham-5 knockout mutant. A single blot is shown in which a mak-2 mutant (lane 1), the wild-type (lane 2), and ham-5 knockout mutant (lane 3) were tested for the presence of activated MAK-1 and MAK-2. A positive control containing phosphorylated p42 MAP kinase (Erk2) is shown in lane 4. The arrows show the positions of MAK-2 (41 080 Da) and MAK-1 (51 580 Da).
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References

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