Fig 8.

Schematic representation of the regulatory role of the light signaling machinery in MAT1-1 and MAT1-2 strains. Both pheromone precursors and receptors are influenced by the photoreceptors BLR1 and BLR2, likely via their impact on ENV1. The impact of the light response machinery is to a certain extent mating type dependent. In the MAT1-1 strain, the light signaling machinery predominantly acts on ppg1 transcription and on transcript levels of the pheromone receptor presumably receiving the HPP1 (MAT1-2 mating type) signal, hpr1. In contrast, BLR1, BLR2, and ENV1 in the MAT1-2 background more strongly act on transcript levels of hpp1 and the cognate receptor of the MAT1-1 pheromone precursor PPG1, hpr2. This strong effect on hpp1 in this mating type is also reflected in earlier and more vigorous fruiting body formation of the Δenv1 strain with the wild-type strain. The strong effect of ENV1 indicates that this factor may act as a node integrating mating signals with the nutrient signaling pathway. The pale arrows indicate this hypothesis, which remains to be proven.