Polarisation and asymmetrical division generating the Poaceous subsidiary cells constitutes a very attractive model for the study of local intercellular stimulation. Auxin operates as an inductive stimulus while PIN auxin carriers and reactive oxygen species seem to facilitate signal transduction.
Specific cell wall components and the SCAR/WAVE complex are emerging as the earliest polarization factors described so far. Other proteins such as the leucine-rich receptor-like kinases PAN1 and PAN2, Rho-like GTPases of plants, the phosphatidyl-inositol-3-kinase and phospholipases C and D also participate in the transmission of the extrinsic signal that polarizes the asymmetric division. Apostolakos et al. summarize findings derived mostly from Zea mays and provide an overall perspective view of these phenomena.