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.
Bottom Line: 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.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.
Affiliation: Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, 1060, Austria.Show MeSH
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Mentions: In order to test whether KAP8 is indeed essential for XYR1 uptake into the nucleus, we expressed a GFPXYR1 fusion protein in T. reesei Δkap8 and its complemented transformant and monitored its subcellular localization under inducing conditions. As reported previously (Lichius et al., 2014), nuclear import of XYR1 in response to a cellulase inducing signal is essential to activate xyr1 expression in an auto-regulatory manner and hence to produce sufficient amounts of XYR1 to elicit high-level cellulase and hemicellulase gene expression. As shown in Fig. 2, fluorescence microscopy demonstrated that the parent strain and the kap8 complemented transformant imported XYR1 into the nuclei, whereas Δkap8 did not. These data show that nuclear import of XYR1 is dependent on KAP8 function.
Affiliation: Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, 1060, Austria.