YODA signalling in the early Arabidopsis embryo.

During early embryogenesis, flowering plants establish their principal body plan starting with an apical-basal axis. An asymmetric division of the zygote gives rise to apical and basal cells with different developmental fates. Besides WOX (WUSCHEL-RELATED HOMEOBOX) transcription factors and the plant hormone auxin, the YDA (YODA)/MAPK (mitogen-activated protein kinase) pathway plays a major role in establishing different cell fates after the first zygotic division. In the present review, we summarize the available data on YDA signalling during embryogenesis. The role of YDA in other developmental processes was taken into account to highlight possible implications for this pathway in the embryo.