Figure 8

Schematic drawing of the current model for the interrelationship between nutrient and light signaling in T. reesei . The regulatory interplay between nutrient and light signalling involves a limb represented by components of the heterotrimeric G-protein pathway and a limb established by the crucial components of the light response machinery. Central interactors of this connection are ENV1 and PhLP1. The positive effect of PhLP1 on env1 transcription in early light regulation (ELR) may be responsible for negative regulation of heterotrimeric G-protein signalling by ENV1. The effect of ENV1 on gnb1 and gng1 is mediated by PhLP1. Investigation of the effect of constitutive activation of the G-alpha subunits GNA1 and GNA3 on regulation of phlp1 transcript levels showed that the nutrient signals transmitted by GNA1 and GNA3 impact phlp1. Both the light signalling components as well as the factors of heterotrimeric G-protein pathway analyzed in this study were found to dampen light responsiveness of transcript abundance and are likely to constitute a light specific regulatory mechanism sustaining transcript levels of downstream genes relevant during growth in light. Investigation of the cAMP pathway as depicted in this scheme was described earlier [26]. Arrows indicate positive influence while plungers indicate a negative effect. Dashed lines show hypotheses deduced from results in other fungi (discussed in [26]). Asterisks indicate an effect on light responsiveness of transcript levels.