Fig. 7: Schematic illustration of cell wall pattern formation in metaxylem vessels.

a KNAT7 suppresses the expression of FH11 in the metaxylem vessels of wild-type plants, causing a pitted cell wall pattern to form. Secondary cell walls are deposited on microtubules. Active ROPs localize to spots on the plasma membrane where the microtubules are depolymerized through the MIDD1-Kinesin-13A pathway, ultimately leading to the formation of pits at points where the secondary cell wall is not deposited. Actin rings form around the spots of active ROPs and promote the deposition of secondary cell wall at pit boundaries. b In metaxylem vessels of knat7, misexpression of FH11 leads to the formation of a banded cell wall pattern. FH11 promotes the polymerization of cortical actin filaments, which disperses the ROP domains. c Dimeric FH11 on the plasma membrane promotes the polymerization of cortical actin filaments from monomeric actin bound to profilin. The extracellular domain of FH11 may interact with the cell wall matrix.