Evidence for Transceptor Function of Cellodextrin Transporters in Neurospora crassa

The Putative Cellodextrin Transporter-like Protein CLP1 Is Involved in Cellulase Induction in Neurospora crassa

“…CLP1 Suppresses Cellulase Induction; Co-disruption of cdt2 and clp1 in ⌬3␤G Significantly Increases Cellulase InductionBecause cellobiose can efficiently induce cellulase production in the ⌬3␤G mutant, in which the three main ␤-glucosidase genes (gh1-1, gh3-4, and gh3-3) are deleted, it is a very good system to investigate the molecular basis of the cellulase induction pathway (3,17). To test the alternative hypothesis that CLP1 might play a role in signaling transduction during cellulase induction by cellodextrin, we constructed seven series mutants with one to multiple genes disrupted in the ⌬3␤G strain background ( Table 1).…”

“…Proteins such as Snf3 and Rgt2 in Saccharomyces cerevisiae and RCO3 in N. crassa have been identified as glucose sensors (7)(8)(9) but have no glucose transport activity. Alternatively, there is also a group of membrane proteins that could serve as molecule sensors and transporters, called transceptors (10); the sensing and transport might not be the same molecule, for example, Crt1 in T. reesei (3,4,11). The detailed working mechanism of sugar transceptors is not known very well.…”

“…As yet seven oligosaccharide transporters from filamentous fungi have been shown to be involved in cellulose degradation and cellulase induction, including CDT1 and CDT2 in Neurospora crassa (2,3), Stp1 and Crt1 in Trichoderma reesei (4), and CdtC, CdtD, and CdtG in Penicillium oxalicum (5). CDT1 and CDT2 were the first cellodextrin transporters identified to play an important role in cellulase production and cellulose degradation in N. crassa, especially CDT2.…”

Transcriptional Regulation and Responses in Filamentous Fungi Exposed to Lignocellulose

“…This 'transceptor' concept is significant as it shifts the model of regulation of transporters to include the regulation of the sensing as well as the transport of small molecules. In N. crassa, a recent study showed how the cellodextrin transporters CDT-1 and CDT-2 could function as 'transceptors' [132]. When CDT-1 and CDT-2 were mutated to remove their ability to transport cellobiose, the cellulase gene induction was not correspondingly reduced indicating a secondary sensing and signalling role for the transporters [132].…”

“…Znameroski et al [132] described other studies in the literature regarding 'transceptors' relevant to the response of T. reesei to lignocellulose. Whilst there is indirect evidence supporting 'transceptors' in the examples from N. crassa and T. reesei, direct evidence as far as we are aware for the molecular basis of the signalling role of these 'transceptors' related to lignocellulose is lacking.…”