ABSTRACT
Abstract@#Transmission of extracellular signal across the plasma membrane into the cells of organisms is impossible without cell surface receptors. One of the most broadly studied receptor is the G-protein coupled receptor. This receptor is coupled with heterotrimeric G proteins with α, β and γ subunits that perceives external stimuli and transduces the signal into the cell for suitable physiological and biochemical responses. They have also been reported as potential receptors to sense light and fatty acids, but their exact mechanism remains unclear in fungi. Signalling and regulation via G proteins has been extensively studied in various models including pathogenic fungi. Fungal GPCRs are broadly required in fungal defence stimulation, vegetative growth, and pathogenicity mechanism. This review aims to highlight the research in fungal GPCRs including classification, physiological roles, mechanisms of action and signalling in GPCR function. Through fungal genome sequencing, mammalian GPCRs have been identified apart from fungal-specific GPCRs which adds another dimension to the classification. The deorphanisation of unclassified fungal GPCRs is necessary to further understand their role in fungi. While the mechanism of action has been well documented in mammals, the glucose and pheromone sensing are the only two well mapped systems in yeast. However, we are yet to ascertain if there are any additional mechanisms of signalling at work in fungi. Further we endeavour to compare and contrast between the eukaryotic GPCRs in various aspects of functionality. Through the information derived we hope to determine the gaps in knowledge and by so doing determine the future directions of GPCR research in fungi.
ABSTRACT
Background In the industrial biotechnology, ligninolytic enzymes are produced by single fungal strains. Experimental evidence suggests that co-culture of ligninolytic fungi and filamentous microfungi results in an increase laccase activity. In this topic, only the ascomycete Trichoderma spp. has been studied broadly. However, fungal ligninolytic-filamentous microfungi biodiversity interaction in nature is abundant and poorly studied. The enhancement of laccase and manganese peroxidase (MnP) activities of Trametes maxima as a function of time inoculation of Paecilomyces carneus and under several culture conditions using Plackett-Burman experimental design (PBED) were investigated. Results The highest increases of laccase (12,382.5 U/mg protein) and MnP (564.1 U/mg protein) activities were seen in co-cultures I3 and I5, respectively, both at 10 d after inoculation. This level of activity was significantly different from the enzyme activity in non-inoculated T. maxima (4881.0 U/mg protein and 291.8 U/mg protein for laccase and MnP, respectively). PBED results showed that laccase was increased (P < 0.05) by high levels of glucose, (NH4)2SO4 and MnSO4 and low levels of KH2PO4, FeSO4 and inoculum (P < 0.05). In addition, MnP activity was increased (P < 0.05) by high yeast extract, MgSO4, CaCl2 and MnSO4 concentrations. Conclusions Interaction between indigenous fungi: T. maxima-P. carneus improves laccase and MnP activities. The inoculation time of P. carneus on T. maxima plays an important role in the laccase and MnP enhancement. The nutritional requirements for enzyme improvement in a co-culture system are different from those required for a monoculture system.