Trichoderma reesei xylanase expression "what makes the difference in inducer recognition"

15.10.2007 - 14.10.2011
Research funding project
T. reesei xylanase expression: Different inducer recognition Filamentous ascomycetes of the genus Trichoderma mainly act as saprophytes thereby degrading a wide variety of bio-polymeric substrates such as cellulose and hemicelluloses, predominant components of plant material. Hemicellulose as a collective term summarizes a variety of heteropolysaccharides composed either of a backbone formed by xylose (xylans) or mannose and glucose (mannans, glucomannans) with additional side chain substitutes such as arabinose, galactose, and acetic or glucuronic acid. Hemicelluloses are largely water insoluble hence their hydrolysis sets a challenge for saprophytes. Complete degradation of hemicelluloses requires a large number of extracellular enzymes working in synergistic action to allow hydrolysis to smaller oligosaccharides and finally to the respective monomers. In research on regulation of production of hemicellulolytic enzymes in filamentous fungi, Trichoderma has - together with Aspergillus - the leading role. Significant progress has been made during the last few years in the identification and characterisation of in cis-acting elements and in trans-acting factors regulating xylanase expression. In Trichoderma, the general regulator of hydrolase formation (Xyr1) seems to be directly modulated in its mode of action by additional narrow domain transcription factors such as Ace1 and Ace2. Even though the binding-elements are highly similar, DNA-contact of these two factors is dedicated to only either one of the promoters of the two major xylanolytic genes (i.e. Ace1 with pxyn1 and Ace2 with pxyn2). First investigations revealed a spectrum of different mechanisms modifying the Xyr1-dependent transcriptosomes of xyn1 and xyn2 respectively, including phosphorylation, competition, homo- and hetero- dimerisation and recruiting of additional regulatory proteins. At the current state of investigations deduced models for the assembling and modification of both transcriptosomes exist, but those working hypotheses still miss substantial experimental proof. To further elucidate this complex interplay of regulatory proteins the following main questions are addressed in this research project: i) is Ace1 modified to achieve its active form and/or what is the role of the Ace1 interacting protein (Aip) in this repressor complex? ii) Does the Ace1/Aip heterodimer bind to Xyr1 or is it simply competing out the second Xyr1 of the induction-specific protein-DNA complex? iii) is homodimerisation of Xyr1 the precondition for xyn1 induction or is the mechanism based upon competition between a second Xyr1 and the Ace1/Aip repressor complex? iv) does Ace2 form a heterodimer with Xyr1? V) What are the modifications and interaction partners of the Ace2/Xyr1 ¿ DNA complex enabling the various steps of xyn2 transcriptional regulation? vi) compare the assembly of the xyn2 transcriptosome in an ace2 deletion strain (having lost several facets of transcriptional regulation but still expressing xyn2) with the WT. vii) compare the assembly of the sophorose dependent with the xylobiose-dependent transcriptosome in the xyn2 promoter

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Grant funds

  • FWF - Österr. Wissenschaftsfonds (National) Austrian Science Fund (FWF)

Research focus

  • Biological and Bioactive Materials: 100%

Keywords

GermanEnglish
TrichodermaTrichoderma
HydrolasenHydrolases
Genregulationgene regulation
TranskriptionsfaktorenTranscription Factors

Publications