PLANT-CELL MORPHOGENESIS - PLASMA-MEMBRANE INTERACTIONS WITH THE CYTOSKELETON AND CELL-WALL

Because plants are composed of immobile cells, plant morphogenesis req uires mechanisms allowing precise control of cell expansion and cell d ivision patterns. Cortical domains, localized in response to direction al cues, are of central importance in establishing cell polarity, orie nting cell division, and determining daughter cell fates in a wide var iety of prokaryotic and eukaryotic organisms. Such domains consist of localized macromolecular complexes that, in plant cells, provide spati al control of cell expansion and cell division functions. The role of the cytoskeleton, plasma membrane, and targeted secretion to the cell wall in the spatial regulation of cell morphogenesis in plants is disc ussed in light of recent results from model organisms, including brown algal zygotes (e.g. Fucus). A general model, emphasizing the importan ce of cortical sites and targeted secretion, is proposed for morphogen esis in higher plant cells based on current knowledge and principles d erived from analysis of the establishment of a stable cortical asymmet ry in Fucus. The model illustrates mechanisms to direct the orientatio n of an asymmetric division resulting in daughter cells with different fates.