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 S. cerevisiae, Kap121 is essential for the nuclear import of the oxidative stress regulator Yap1 (Isoyama et al., 2001) and the antibiotic efflux regulator Pdr1 (Delahodde et al., 2001; Caudle et al., 2011). We have therefore investigated whether the deletion of T. reesei kap8 might have an effect on its response to stress. To this end, we cultivated T. reesei Δkap8 and its complemented transformant under conditions known to elicit a stress response, such as high concentrations of sorbitol and KCl (osmotic and salt stress), extreme pH, growth-inhibiting temperature (37°C), fluconazole (azole toxicity) and H2O2 (oxidative stress). The results, shown in Fig. 6, document that indeed the Δkap8 strain exhibits significantly decreased growth under all these conditions, but the effect was most severe under osmotic stress, at low pH (pH2) and at elevated temperature (37°C). In contrast to what is observed in A. nidulans (Etxebeste et al., 2009), none of these stress conditions rescued the sporulation deficiency of the Δkap8 strain.
Affiliation: Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, 1060, Austria.