Abstract

Interactions among key regulators of Arabidopsis gynoecium development have revealed a network of transcription factor activities required for dividing this organ into discrete domains. Regulation of auxin dynamics is emerging as an immediate downstream output from these activities. We aim to understand the spatiotemporal information that is defined through interactions between a set of transcription factors and auxin during the gynoecium patterning process. At the gynoecium apex, our data suggest that auxin is recruited to promote an unusual symmetry transition. We hypothesise that this is required to eliminate a default state of bilateral symmetry engrained in the gynoecium from its origin as two fused leaves.

Auxin signaling occurs through binding of the auxin molecule to a TIR1 /AFB F-box protein allowing interaction with Aux/IAA transcriptional repressor proteins. These are subsequently degraded via the 26S proteasome leading to de-repression of auxin response factors (ARFs). How auxin is able to elicit such a diverse range of developmental responses through a single signalling module remains largely unclear. We have identified an alternate auxin-signalling mechanism comprised of a co-receptor complex involving the transcription factors ETTIN and INDEHISCENT directly binding the auxin molecule. This auxin co-receptor is important for coordinated development of tissues in the Arabidopsis female reproductive organ – the gynoecium. Disrupting the auxin-binding capacity of this co-receptor compromises development of the apical tissues of the gynoecium severely affecting plant fertility.