Figure 3.

Model for D14L signalling in conditioning of plants for AM symbiosis. D14L signalling leads to the removal of the repressor SMAX1 and to the upregulation of the expression of CSSP components, increased SL biosynthesis, and increased expression of GA biosynthesis genes. This D14L activity creates a permissive state of the plant for AM symbiosis, setting the scene for presymbiosis signalling with AM fungi. During presymbiosis, the biochemical communication between the plant and the AM fungus activates the CSSP in preparation for accommodation. Once committed, formation of penetrative structure, the hyphopodium, occurs and the activated accommodation programme enables the establishment of AM symbiosis. However, in the absence of D14L signalling, the accumulation of SMAX1 results in a non-permissive condition for AM symbiosis development.