Differential hyphal morphogenesis in arbuscular mycorrhizal fungi during pre-infection stages.

Roots of host plants elicit a local change in morphology in the hyphae of arbuscular mycorrhizal fungi, prior to the formation of appressoria. The elicited hyphae switch from their original branching pattern and apical dominance to differentiate in a new irregular, septate branching pattern with reduced inter-hyphal spacing. The extensive hyphal development associated with roots of host plants was shown to be due to the differential growth pattern described, and to precede the further cascade of events leading to appressorium formation and the development of a functional symbiosis.