FIGURE 2.

Pre-symbiotic induction of lateral root formation in arbuscular mycorrhiza. Germinating spore exudates (GSE) contain Myc-LCOs and possibly phytohormone-like compounds. Perception of Myc-LCOs leads to lateral root induction in Medicago truncatula, which requires the common symbiosis signaling components DMI1, DMI2, and DMI3 (brown pathway). The green pathway hypothesizes phytohormone-like signaling to operate either downstream or independent of common symbiosis signaling in M. truncatula and rice, respectively.