Genetic integration of DORNROSCHEN and DORNROSCHEN-LIKE reveals hierarchical interactions in auxin signalling and patterning of the Arabidopsis apical embryo

DORNRA-SCHEN (DRN) and DORNRA-SCHEN-LIKE (DRNL) encode AP2-domain transcription factors, which act redundantly in cotyledon organogenesis. A more detailed genetic study now integrates DRN and DRNL into the CUP-SHAPED COTYLEDON (CUC) regulatory network and places DRN and DRNL differentially within the auxin signalling network: DRNL function overlaps with that of PIN-FORMED1, and DRN with PINOID. DRN and DRNL act cell-autonomously and are co-expressed in the early globular embryo, whereas expression patterns diverge during later stages of embryogeny. Both genes synergize to provide essential patterning information in the apical embryo domain, to establish correct CUC, SHOOTMERISTEMLESS and WUSCHEL expression domains, which relates to the patterning of SAM anlagen to a central apical position to create two planes of bilateral symmetry in wild type Arabidopsis thaliana embryos.