GSE59600
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
The ascomycete Trichoderma reesei is an industrial producer of cellulolytic and hemicellulolytic enzymes and also serves as a model for investigations on these enzymes and their genes. Most of them are obligatorily dependent on the Zn(II)Cys(VI) transcriptional activator XYR1. XYR1 is constitutively expressed at a low basal, but induced in the presence of cellulase- and hemicellulose inducers, and transported into the nucleus. The factors mediating its import and export across the nuclear pore complexes (karyopherins) are therefore expected to play a key role in its function. We identified 14 karyopherins in T. reesei, of which 8 were predicted to be involved nuclear protein import. Their systematic knock-out and testing for cellulase formation identified KAP8 (an orthologue of A. nidulans KapI, and Saccharomyces cerevisiae Kap121/Pse1p) to be essential for cellulase gene expression, and for the appearance of GFP-XYR1 in the nucleus. Transcriptomic analysis of ?kap8 and a retransformant under cellulase-inducing conditions revealed the downregulation of 64 Cazymes in the ?kap8 strain under inducing conditions, including all cellulases and hemicellulases known to be under XYR1 control, and of 12 transcription factors of which 2 were known to be associated with cellulase regulation (ACE3, CLR2). Together, these new observations underscore the role of nuclear transport of XYR1 in the regulation of cellulase and hemicellulose gene expression in T. reesei, and identify KAP8 as the major karyopherin involved in this process. Overall design: Two strains were used: T. reesei ku70 (pyr4-), in which the kap8 (=kapI/Pse1/Kap121) reading frame has been replaced by the T. reesei pyr4 gene; and a kap8-retransformant of the same strain and two time points for each strain T0h and T3h. All samples are in tricplicate.