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Title: HAM-5 functions as a MAP kinase scaffold during cell fusion in Neurospora crassa

Journal Article · · PLoS Genetics
 [1];  [1];  [2];  [2];  [3];  [1];  [2];  [2];  [1];  [4]
  1. Univ. of California, Berkeley, CA (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Genentech, South San Francisco, CA (United States)
  4. Duke Univ. Medical Center, Durham, NC (United States)

© 2014. Cell fusion in genetically identical Neurospora crassa germlings and in hyphae is a highly regulated process involving the activation of a conserved MAP kinase cascade that includes NRC-1, MEK-2 and MAK-2. During chemotrophic growth in germlings, the MAP kinase cascade members localize to conidial anastomosis tube (CAT) tips every ~8 minutes, perfectly out of phase with another protein that is recruited to the tip: SOFT, a recently identified scaffold for the MAK-1 MAP kinase pathway in Sordaria macrospora. How the MAK-2 oscillation process is initiated, maintained and what proteins regulate the MAP kinase cascade is currently unclear. A global phosphoproteomics approach using an allele of mak-2 (mak-2 Q100G ) that can be specifically inhibited by the ATP analog 1NM-PP1 was utilized to identify MAK-2 kinase targets in germlings that were potentially involved in this process. One such putative target was HAM-5, a protein of unknown biochemical function. Previously, Δham-5 mutants were shown to be deficient for hyphal fusion. Here we show that HAM-5-GFP co-localized with NRC-1, MEK-2 and MAK-2 and oscillated with identical dynamics from the cytoplasm to CAT tips during chemotropic interactions. In the Δmak-2 strain, HAM-5-GFP localized to punctate complexes that did not oscillate, but still localized to the germling tip, suggesting that MAK-2 activity influences HAM-5 function/localization. However, MAK-2-GFP showed cytoplasmic and nuclear localization in a Δham-5 strain and did not localize to puncta. Via co-immunoprecipitation experiments, HAM-5 was shown to physically interact with NRC-1, MEK-2 and MAK-2, suggesting that it functions as a scaffold/transport hub for the MAP kinase cascade members for oscillation and chemotropic interactions during germling and hyphal fusion in N. crassa. The identification of HAM-5 as a scaffold-like protein will help to link the activation of MAK-2 cascade to upstream factors and proteins involved in this intriguing process of fungal communication.

Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
Grant/Contract Number:
AC05-76RL01830; AC02-05CH11231
OSTI ID:
1166844
Alternate ID(s):
OSTI ID: 1407220
Report Number(s):
PNNL-SA-103955; 48135; 400412000
Journal Information:
PLoS Genetics, Vol. 10, Issue 11; ISSN 1553-7404
Publisher:
Public Library of ScienceCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 55 works
Citation information provided by
Web of Science

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New insights from an old mutant: SPADIX4 governs fruiting body development but not hyphal fusion in Sordaria macrospora journal October 2016
The HamE scaffold positively regulates MpkB phosphorylation to promote development and secondary metabolism in Aspergillus nidulans journal November 2018
NLR surveillance of essential SEC-9 SNARE proteins induces programmed cell death upon allorecognition in filamentous fungi journal February 2018
Involvement of MAK-1 and MAK-2 MAP kinases in cell wall integrity in Neurospora crassa journal June 2016
Identification of Allorecognition Loci in Neurospora crassa by Genomics and Evolutionary Approaches journal May 2015
Transcription factor PRO1 targets genes encoding conserved components of fungal developmental signaling pathways journal September 2016
Cellulases and beyond: the first 70 years of the enzyme producer Trichoderma reesei journal June 2016
Restoration of female fertility in Trichoderma reesei QM6a provides the basis for inbreeding in this industrial cellulase producing fungus journal September 2015
Gene regulation associated with sexual development and female fertility in different isolates of Trichoderma reesei journal May 2018
Spatio-temporal MAPK dynamics mediate cell behavior coordination during fungal somatic cell fusion journal March 2018
Molecular mechanisms of chemotropism and cell fusion in unicellular fungi journal May 2019
Characterization of Greenbeard Genes Involved in Long-Distance Kind Discrimination in a Microbial Eukaryote journal April 2016
Fungal Communication Requires the MAK-2 Pathway Elements STE-20 and RAS-2, the NRC-1 Adapter STE-50 and the MAP Kinase Scaffold HAM-5 journal November 2014
Regulation of Cell-to-Cell Communication and Cell Wall Integrity by a Network of MAP Kinase Pathways and Transcription Factors in Neurospora crassa journal April 2018
Integration of Self and Non-self Recognition Modulates Asexual Cell-to-Cell Communication in Neurospora crassa journal February 2019
PaPro1 and IDC4, Two Genes Controlling Stationary Phase, Sexual Development and Cell Degeneration in Podospora anserina journal July 2018
The HamE scaffold positively regulates MpkB phosphorylation to promote development and secondary metabolism in Aspergillus nidulans journal March 2019
The Neurospora Transcription Factor ADV-1 Transduces Light Signals and Temporal Information to Control Rhythmic Expression of Genes Involved in Cell Fusion journal November 2016
Communicate and Fuse: How Filamentous Fungi Establish and Maintain an Interconnected Mycelial Network journal March 2019
WHI-2 Regulates Intercellular Communication via a MAP Kinase Signaling Complex journal January 2020