The Department of Biochemistry's weekly BCH 252 seminar series is presented this week by:

Logan Collier, BCMB Graduate Student, UC Riverside 

Seminar Title: "cAMP-Dependent G Protein Signaling is Required for Cellulose Degradation in Neurospora crassa"

Abstract: 

Logan Collier^1,2 Arit Ghosh², and Katherine A. Borkovich^1,2

¹Graduate Program in Biochemistry and Molecular Biology and    ²Department of Microbiology and Plant Pathology, University of California, Riverside, Riverside, California 92521 

The filamentous fungus Neurospora crassa is able to decompose lignocellulosic plant matter to generate sugars as carbon sources. In this study, we investigated a possible role for heterotrimeric G protein signaling in regulating cellulose utilization and degradation. We observed that the absence of the Gα subunits gna-1 and gna-3, the Gβ subunits gnb-1 and cpc-2, the Gγ gng-1, or the downstream effector enzyme adenylyl cyclase (cr-1) results in the inability to completely degrade cellulose into glucose. Additionally, the level of secreted protein is reduced, and secretomes from these mutants have no detectable cellulase activity. Analysis of the expression patterns of five cellulase genes showed that Δgna-1, Δgnb-1 and Δgna-3 mutants produce much less mRNA than wild type, consistent with transcriptional regulation of cellulase gene expression. In contrast, Δcpc-2 and Δcr-1 mutants had wild-type levels of cellulase transcripts, suggesting a post-transcriptional control mechanism. Addition of cAMP to the medium remediated the phenotypes of Δgna-1, Δgnb-1, Δgna-3, and Δgna-3 mutants, consistent with a scenario in which these G protein subunits function upstream of cAMP signaling. Finally, we observed that levels of all three Gα proteins are reduced in Δgnb-1 and Δgng-1 mutants, likely contributing to the defect in cellulase activity observed in these strains. Taken together, these results suggest that cAMP-dependent G protein signaling is required for both transcriptional and post-transcriptional control of secreted cellulase enzymes in N. crassa.

Faculty Host: Dr. Sean O'Leary, sean.oleary@ucr.edu