Developmental cartography: coordination via hormonal and genetic interactions during gynoecium formation

- Auxin and cytokinin show both overlapping and non-overlapping distribution patterns.
- Flux-based mechanisms are likely important to establish gynoecium tissue domains.
- Auxin and cytokinin provide positional information and identity via feedback loops.
- Non-canonical hormonal sensing mechanisms infer and translate positional information.

Development in multicellular organisms requires the establishment of tissue identity through polarity cues. The Arabidopsis gynoecium presents an excellent model to study this coordination, as it comprises a complex tissue structure which is established through multiple polarity systems. The gynoecium is derived from the fusion of two carpels and forms in the centre of the flower. Many regulators of carpel development also have roles in leaf development, emphasizing the evolutionary origin of carpels as modified leaves. The gynoecium can therefore be considered as having evolved from a simple setup followed by adjustment in tissue polarity to facilitate efficient reproduction. Here, we discuss concepts to understand how hormonal and genetic systems interact to pattern the gynoecium.