Mating Type Gene Homologues and Putative Sex Pheromone-Sensing Pathway in Arbuscular Mycorrhizal Fungi, a Presumably Asexual Plant Root Symbiont
Figure 2
Hypothetical pheromone sensing pathway in Rhizophagus irregularis.
A putative pheromone binds to its receptor (STE3) that is coupled to a heterotrimeric G-protein designated GPA1 (α-subunit), STE4 (β-subunit), and STE18 (γ-subunit). The putative pheromone binding to its receptor leads to G-protein activation and the dissociation of STE4 and STE18 from Gpa1. The released complex (STE4/STE18) activates STE20 that stimulates the MAPK module MKKK STE11, MKK STE7 and MAPK FUS3. The activated form of FUS3 may be translocated to the nucleus, where it activates STE12. STE12 induces putative transcriptional factors of the Pheromone Response Element that activates the SexM or SexP gene. Activation of STE 11 could also be achieved by an independent putative mechanism involving STE50 through the activation of STE20.
