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. 2020 Oct 12;477(19):3743–3767. doi: 10.1042/BCJ20190161

Figure 2. Some key events during early embryogenesis in Arabidopsis.

Figure 2.

The mature egg cell is polarized (not shown) but after fertilization undergoes a more symmetric stage. Repolarization of the zygote occurs and involves a signaling pathway that includes SSP kinase (translated in the zygote from SSP mRNA delivered by the sperm). A YDA/MAP kinase signaling cascade ensues, leading to phosphorylation of WRKY2 that then expresses WOX8. WOX2 and WOX8 are present in the zygote, but after the first division, WOX2 is in the AC and WOX8 in the BC. PIN7 efflux auxin carrier moves auxin into the AC/EP, until a reversal at the dermatogen stage, when auxin begins being synthesized in the EP and basipetally distributed. At the dermatogen stage, MP marks the inner cells, and PDF2/ATML1 the protoderm. PIN1, controlled by MP is involved in polar auxin transport. PIN1 and TMO7 are regulated by MP in the EP and TMO7 moves to the top suspensor cell/hypophysis, and along with auxin specifies this cell. ARF9/IAA10 is also important for this process. Not all genes involved, nor all localizations/interactions are shown in order to maintain clarity. For example, PIN1 accumulates earlier than the 32-cell stage, but is more randomly localized.