G protein-cAMP signaling pathway mediated by PGA3 plays different roles in regulating the expressions of amylases and cellulases in Penicillium decumbens

Abstract Heterotrimeric G proteins (G proteins) have been extensively investigated for their regulatory functions in morphogenesis and development in filamentous fungi. In addition, G proteins were also shown to be involved in the regulation of cellulase expression in some fungi. Here, we report the different regulatory effects of PGA3, a group III G protein α subunit, on the expressions of amylases and cellulases in Penicillium decumbens . Deletion of pga3 resulted in impaired amylase production and significantly decreased transcription of the major amylase gene amy15A . Supplementation of exogenous cAMP or its analog dibutyryl-cAMP restored amylase production in Δ pga3 strain, suggesting an essential role of PGA3 in amylase synthesis via controlling cAMP level. On the other hand, the transcription of major cellulase gene cel7A-2 increased, nevertheless cellulase activity in the medium was not affected, in Δ pga3 . The above regulatory effects of PGA3 are carbon source-independent, and are achieved, at least, by cAMP-mediated regulation of the expression level of transcription factor AmyR. The functions of PGA3 revealed by gene deletion were partially supported by the analysis of the mutant carrying dominantly-activated PGA3. The results provided new insights into the understanding of the physiological functions of G protein-cAMP pathway in filamentous fungi.