Figure 2.

Schematic model of the proposed function of GNA3. Upon activation by its cognate G-protein coupled receptor (GPCR), GNA3 causes increased cAMP-levels and acts on its downstream effector. These events result in positive modulation of cellulase gene transcription, the induction of which is initiated by an as yet unidentified pathway. Transcription of gna3 is enhanced by light, negatively regulated by ENVOY and activation of GNA3 is decreased by a regulator of the G-protein signalling protein. The GNA3 downstream pathway leading to modulation of cellulase gene transcription is perturbed in darkness.