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Previous work from our group reveals that filamentous fungi utilize G-protein signaling for cellulose sensing and degradation. The primary objectives of this dissertation are: 1. to determine the role of Regulator of G-protein Signaling (RGS) proteins in the regulation of Gα subunits during growth on cellulose, 2. to elucidate global transcriptional regulation by G-protein subunits and their downstream effectors on cellulose, and 3. to examine regulation of specific cellulase enzyme families by G-proteins, RGS proteins, and adenylyl cyclase.In Chapter 2, we characterized the role of RGS proteins in growth, development, and cellulase activity in N. crassa. Through direct inoculation into Avicel (cellulose), I showed that RGS-2 is essential for Avicelase activity. I also found RGS-1 and RGS-4 as negative, and RGS-3 as positive regulator of Avicelase activity. RGS-1 negatively regulated culture biomass on Avicel while RGS-2, RGS-3, and RGS-7 were positive regulators.Chapter 3 involved analysis of global transcriptomes of Δgna-1, Δgna-3, and Δcr-1 mutants grown on glucose and cellulose. Upon comparing the transcriptomes of mutants to wild-type strain, I found that GNA-3 regulates the greatest number of genes on glucose, while the adenylyl cyclase CR-1 regulates the most genes on cellulose. I identified that over-expression of CLR-2, a transcriptional regulator of cellulases, rescued Avicelase activity in Δgna-1 and Δgna-3 mutants to nearly wild-type levels. I also acquired evidence about the role of CLR-2 in deregulation of macro-conidiation in submerged cultures through VIB-1. In Chapter 4, I performed specific cellulase assays for endoglucanases (EG), cellobiohydrolases (CBH), and β-glucosidases (BG) on G-protein single and multiple gene deletion mutants, RGS mutants, the cr-1 mutant, and GTPase-deficient Gα strains. Major results show that CR-1 regulates CBH activity through GNA-2 and GNA-3. I also show that GNA-1 and GNA-3 together regulate EG activity. RGS proteins are observed to regulate cellulase enzyme activities to a moderate level. The GTPase-deficient gna-1 allele showed elevated EG and CBH activities. These results show that G-protein signaling contributes more to EG and CBH activities than to BG activity.Overall, this dissertation identifies the role of RGS proteins in cellulose degradation and elucidates the regulation of cellulase activity by G-proteins in further depth.