Signalling process and activation of Slt A, a transcription factor involved in cation /alkalinity stress response

Ref ID: 19534


L Mellado1*, HN Arst2, EA Espeso1

Author address:

1Cellular and Molecular Biology, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain
2Microbiology, Imperial College London, London, United Kingdom

Full conference title:

6th Advances Against Aspergillosis 2014


To sense and adapt to abiotic stress conditions some fungi, such as Aspergillus nidulans, have
developed regulatory mechanisms to control gene expression. Cation and alkaline pH stress
responses are mediated by diverse pathways in A. nidulans. We focus on the signalling process and
the activation of SltA transcription factor involved in both responses.
Isolation of spontaneous extragenic suppresor mutations of the lethal phenotype caused by certain
null vps alleles, made possible to identify new slt- loci, i.e. sltB. Using reverse genetic strategies we
generated and characterized mutant strains carrying null alleles of sltB and/or sltA to understand their
biological function. Fluorescent and epitope tagged proteins allowed visualization and understanding
its molecular phenotype through immunodetection.
Overexpressing sltB, by means of the ethanol-inducible promoter alcA, we determined the
transcriptional relationships between SltA and SltB in their respective null allele genetic backgrounds.
Here we present our latest model concerning the signalling process and the activation of SltA, in
addition to its transcriptional regulatory activity. Signalling of SltA requires its proteolytic processing,
an extreme mechanism of post-translational modification that shares with PacC. Additionally, we
have discovered and characterised SltB, a signalling element of SltA. sltB gene encodes for a protein
of 1272 amino acids, also specific to filamentous fungi, with two putative functional domains. The
SltB-pseudokinase domain is needed to process the native SltA 78 kDa form into a 32 kDa form.
The second domain is similar to a trypsin-like protease, and our data suggest that SltB undergoes
an auto-proteolytic process through this protease activity. Finally, we have determined that SltB is
expressed in a SltA dependent manner.
A model of regulation of SltA through SltB activity is presented for this novel cation/alkaline pH
regulatory pathway in filamentous fungi.

Abstract Number: 61

Conference Year: 2014

Link to conference website:

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