Establishment of cell polarity during early plant development.

Cellular asymmetries have been proposed to play a role in plant embryogenesis. Genetic studies of Arabidopsis and other experimental approaches in several plant species have addressed the origins of cellular asymmetry in specific cases. Although zygote polarity, which precedes the formation of the apical-basal axis of the embryo, is normally aligned with that of the surrounding maternal tissue, isolated single somatic cells that give rise to embryos in culture appear to become polar in the absence of maternal factors. Gene expression patterns reveal the developmental consequences of cellular asymmetries occurring at later stages of embryogenesis. Genetic evidence suggests that these cellular asymmetries are established in response to as yet unidentified signals from adjacent cells.