title: The ß-importin KAP8 (Pse1/Kap121) is required for nuclear import of the cellulase transcriptional regulator XYR1, asexual sporulation and stress resistance in Trichoderma reesei.
abstract: The ascomycete Trichoderma reesei is an industrial producer of cellulolytic and hemicellulolytic enzymes, and serves as a prime model for their genetic regulation. Most of its (hemi-)cellulolytic enzymes are obligatorily dependent on the transcriptional activator XYR1. Here, we investigated the nucleo-cytoplasmic shuttling mechanism that transports XYR1 across the nuclear pore complex. We identified 14 karyopherins in T. reesei, of which eight were predicted to be involved in nuclear import, and produced single gene-deletion mutants of all. We found KAP8, an ortholog of Aspergillus nidulans KapI, and Saccharomyces cerevisiae Kap121/Pse1, to be essential for nuclear recruitment of GFP-XYR1 and cellulase gene expression. Transformation with the native gene rescued this effect. Transcriptomic analyses of Δkap8 revealed that under cellulase-inducing conditions 42 CAZymes, including all cellulases and hemicellulases known to be under XYR1 control, were significantly down-regulated. Δkap8 strains were capable of forming fertile fruiting bodies but exhibited strongly reduced conidiation both in light and darkness, and showed enhanced sensitivity towards abiotic stress, including high osmotic pressure, low pH and high temperature. Together, these data underscore the significance of nuclear import of XYR1 in cellulase and hemicellulase gene regulation in T. reesei, and identify KAP8 as the major karyopherin required for this process.
authors.affiliation: Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, 1060, Austria.
authors.forename: Sara
authors.initials: S
authors.lastname: Ghassemi
authors.forename: Alexander
authors.initials: A
authors.lastname: Lichius
authors.forename: Fréderique
authors.initials: F
authors.lastname: Bidard
authors.forename: Sophie
authors.initials: S
authors.lastname: Lemoine
authors.forename: Marie-Noëlle
authors.initials: MN
authors.lastname: Rossignol
authors.forename: Silvia
authors.initials: S
authors.lastname: Herold
authors.forename: Verena
authors.initials: V
authors.lastname: Seidl-Seiboth
authors.forename: Bernhard
authors.initials: B
authors.lastname: Seiboth
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Espeso
authors.forename: Antoine
authors.initials: A
authors.lastname: Margeot
authors.forename: Christian P
authors.initials: CP
authors.lastname: Kubicek
mesh_terms: D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D002480:Cellulase / Q000235:genetics* / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D021381:Protein Transport; D012100:Reproduction, Asexual; D013172:Spores, Fungal / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014242:Trichoderma / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D028961:beta Karyopherins / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D014157:Transcription Factors; D028961:beta Karyopherins; D002480:Cellulase