Transcription of the putative maize orthologue of the Arabidopsis DORNRÖSCHEN gene marks early asymmetry in the proembryo and during leaf initiation in the shoot apical meristem

A potential orthologue of the Arabidopsis DORNRÖSCHEN (DRN) gene was isolated from maize based on phylogeny and expression patterns. ZmDRN transcription provides a new marker for embryonic patterning and cellular differentiation in the shoot apical meristem. In contrast to DRN expression in the 2–4-cell Arabidopsis embryo, transcription of the maize orthologue is activated only in the late proembryo stage where expression, however, marks the prospective scutellum domain such as DRN transcription prepatterns cotyledon development in the Arabidopsis globular embryo. The scutellum is commonly considered to be the grass specific organ, which is homologous to the pair of cotyledons in dicots. Such as in Arabidopsis, ZmDRN transcriptional activity is linked to the anlagen of new lateral organs in the maize apex. Striking with respect to the timing of cellular decisions during leaf initiation is asymmetry established between adjacent cells at the very tip of the shoot apical meristem.