Early plant embryogenesis - dark ages or dark matter?

- Polarity establishment during early plant embryogenesis.
- BELL/KNOX proteins contribute to embryogenesis in plants.
- Repression of embryo initiation by YODA signaling pathway.
- Auxin responses in early embryo involved in asymmetric cell division.
- Integration of both YDA signaling and auxin responses at present unclear.

In nearly all flowering plants, the basic body plan is laid down during embryogenesis. In Arabidopsis, the crucial cell types are established extremely early as reflected in the stereotypic sequence of oriented cell divisions in the developing young embryo. Research into early embryogenesis was especially focused on the role of the infamous tryptophan derivative auxin in establishing embryo polarity and generating the main body axis. However, it is becoming obvious that the mere link to auxin does not provide any mechanistic understanding of early embryo patterning. Taking recent research into account, we discuss mechanisms underlying early embryonic patterning from an evolutionary perspective.