Cholesterol and fatty acid homeostasis in mammals is controlled by membrane-bound transcription factors called sterol regulatory element binding proteins (SREBPs). In response to low sterol levels, SREBPs are escorted from the reticulum endoplasmic (ER) membrane to the Golgi apparatus, where a two sequential proteolytic cleavage leads to activation of the transcription factors. SREBP processing depends on the action of SREBP Cleavage-Activating Protein (SCAP), which carries the inactive SREBP precursors to the Golgi complex. Recently, oxygen-dependent sterol synthesis was shown to be an indirect mechanism of oxygen sensing in Schizosaccharomyces pombe. In this work we have identified homologs of SREBPs and SCAP in the filamentous fungus Trichoderma reesei. The structure of TrSREBP is similar to the mammalian isoforms, displaying a basic helix-loop-helix DNA binding domain and two hydrophobic transmembrane spanning segments. We aim to characterize the SREBP pathway in T. reesei in order to investigate the possible involvement of TrSREBP in the mechanisms of oxygen sensing in this microorganism. As would be expected, genes involved in lipid synthesis, such as sterol C-5 desaturase, were transcriptionally induced in the presence of inhibitors of sterol synthesis in T. reesei. On the other hand, the Trsrebp and Trscap genes were induced by low oxygen levels, which suggests that this pathway is activated in response to hypoxia. Moreover, genes induced in a SREBP-dependent manner in mammalian cells, such as sterol C-5 desaturase and squalene epoxidase, were also induced by hypoxia. At the moment we are analyzing the ER-to-Golgi transport of SREBP in sterol-depleted cells and the hypothesis that this transport may also occur in response to low hypoxia. Besides the characterization of an important signaling pathway, this work may contribute to the understanding of how eukaryotic cells sense oxygen levels, a topic with important physiological implications.