Morphogenesis and contact sites in lobed mesophyll cells

The morphogenesis of lobed mesophyll cells (MCs) is highly controlled and coupled with intercellular space formation. Giannoutsou et al. study morphogenesis of lobed MCs of Zea mays and find that it is characterized by early, patterned differentiation of two distinct cell wall subdomains. The first defines the sites of the future MC contacts and is characterized by (1→3, 1→4)-β-D-glucan degradation, the presence of callose and pectins that are recognized by 2F4, LM6, JIM5 and JIM7 antibodies, and the formation of secondary plasmodesmata clusterings. The second defines the positions of cell isthmi and is marked by the presence of (1→3, 1→4)-β-D-glucans and the local deposition of cellulose microfibril rings. This patterned cell wall differentiation precedes the cortical cytoskeleton reorganization, which controls MC morphogenesis.