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Biological Sciences


Thomas M. Hammond

Mentor Department

Biological Sciences


The filamentous fungus Neurospora crassahas been utilized in molecular research for decades, most notably in the fields of genetics and biochemistry. Despite this, Neursopora'sresearch value as a model system has been diminished by its recalcitrance towards expressing certain non-native DNA sequences inserted into its genome. Molecular techniques requiring such heterologous expression are largely incompatible with Neurosporaresearch, despite being successfully implemented in other model systems. We propose this phenomenon results from heretofore unidentified native regulatory mechanisms encoded within the fungal genome which targets heterologous sequences for silencing and is itself susceptible to inactivation through mutation. To test this an experimental transgenic strain was created containing inexpressible cas9sequence fused upstream of the native leucine synthesis gene leu-1. This renders the experimental strain auxotrophic, with a distinct poor growth phenotype in the absence of supplementation due to heterologous silencing activity. By subjecting the clonal conidia spores of the experimental strain to random mutagenesis by UV exposure, we successfully generated a mutant lineage in which heterologous silencing of the construct has been disrupted. Here we demonstrate that this heterologous expression positive (hep) mutation is heritable and resides within the third chromosome of N. crassa.

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