Figure 8. Model for the different mat responses controlled by the MAPK pathway.

Schematic of a mat expanding under nutrient-limiting conditions is shown. Different responses regulated by the MAPK pathway may include: 1) mat expansion in the plane of the XY-axis (surface growth, through Flo11 [23]), 2) cell differentiation that causes invasive growth in the Z-axis (downward growth, Flo11 and differentiation), and 3) upward growth in the plane of the Z-axis in response to surface rigidity and nutrient-limiting conditions (Flo11 and differentiation). This upward growth may represent a type of chemorepulsion. An extracellular matrix (ECM), which may contain shed Flo11 [48] as well as other proteins is depicted.