THE ARABIDOPSIS ERECTA GENE IS EXPRESSED IN THE SHOOT APICAL MERISTEMAND ORGAN PRIMORDIA

In Arabidopsis thaliana (L.) Heynh, the mutation in ERECTA is known to confer a compact inflorescence by a reduction in the lengths of inter nodes and pedicels. We analyzed the expression pattern of this gene du ring plant development. In site hybridization and histochemical analys is using transgenic plants carrying chimeric gene fusions, with the ER ECTA promoter fused to the P-glucuronidase (GUS) gene, showed that ERE CTA was predominantly expressed in the shoot apical meristems and orga n primordia. ERECTA expression in the shoot apical meristem was weak e arly in plant development but increased with the transition from the v egetative to the reproductive growth phase. ERECTA was also strongly e xpressed in organ primordia and immature organs but weakly in mature o rgans. Thus, ERECTA was expressed in a cell-specific and developmental ly regulated manner. In order to identify the regulatory mechanism res ponsible for the expression pattern of ERECTA, the cis-acting regions in the ERECTA promoter were defined by study of the expression of the chimeric genes that consist of the 5'- or internal deleted promoter an d a GUS reporter gene in transgenic plants. The results showed that th e essential cis-regulatory elements governing the spatially and tempor ally specific expression of ERECTA are located between positions -462 and -228 bp and between positions -228 and -153 bp with respect to the transcriptional initiation site.