RESUMO
The SOMATIC EMBRYOGENESIS RECEPTOR KINASE 1 (SERK1) gene is expressed in the procambium of the vascular bundles in roots, hypocotyls, and inflorescence stems. In younger parts of roots and hypocotyls, SERK1 expression was less restricted and was also observed in protoxylem cells, immature metaxylem cells and phloem companion cells. In roots, SERK1 expression was first detected in root vascular stem cells and was notably absent from the QC. In general, the SERK1 protein level as visualized by expression of a SERK1-YFP fusion protein closely followed the pattern of gene expression. In hypocotyls, prolonged application of 2,4-D resulted in extensive unorganized proliferation of SERK1 expressing cells originating from the procambium and pericycle. In roots, 2,4-D treatment results in an increase in SERK1 transcription that results in a moderate increase in the amount of SERK1-YFP fusion protein. The restricted vascular pattern of SERK1 expression in roots remains unaffected after 2,4-D treatment.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Meristema/metabolismo , Proteínas Quinases/metabolismo , Ácido 2,4-Diclorofenoxiacético/farmacologia , Arabidopsis/citologia , Arabidopsis/genética , Proteínas de Arabidopsis/análise , Proteínas de Arabidopsis/genética , Proliferação de Células/efeitos dos fármacos , Flores/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Proteínas Quinases/análise , Proteínas Quinases/genética , Plântula/metabolismo , Xilema/metabolismoRESUMO
From an enhancer trap screen for genes expressed in Arabidopsis embryos, we identified a gene expressed from the octant stage onward in the boundary between the two presumptive cotyledons and in a variety of postembryonic organ and meristem boundaries. This gene, CUP-SHAPED COTYLEDON3 (CUC3), encodes a putative NAC-domain transcription factor that is homologous with CUC1 and CUC2. Analysis of a CUC3 hypomorph and a putative cuc3 null mutant indicates that CUC3 function is partially redundant with that of CUC1 and CUC2 in the establishment of the cotyledon boundary and the shoot meristem, thus revealing an even higher degree of redundancy in this class of genes than was thought previously. The CUC3 expression pattern, the cuc3 phenotypes, and CUC3 expression in a series of shoot meristem mutants and transgenes suggest a primary role for CUC3 in the establishment of boundaries that contain cells with low proliferation and/or differentiation rates. The CUC-mediated establishment of such boundaries may be essential for the initiation of shoot meristems.