RESUMEN

The binding protein BiP is an endoplasmic reticulum (ER)-resident member of the HSP70 stress-related protein family, which is essential for the constitutive function of the ER. In addition to responding to a variety of environmental stimuli, plant BiP exhibits a tissue-specific regulation. We have isolated two soybean BiP genomic clones, designated gsBiP6 and gsBiP9, and different extensions of their 5' flanking sequences were fused to beta-glucuronidase (GUS) reporter gene and introduced into Nicotiana tabacum by Agrobacterium tumefaciens-mediated transformation. Transgenic plants displayed prominent GUS activity in the vascular bundles of roots and shoots as well as in regions of intense cell division, such as procambial region and apical meristems. Promoter deletion analyses identified two cis-regulatory functional domains that are important for the spatially-regulated activation of BiP expression under normal plant development. While an AT-rich enhancer-like sequence, designated cis-acting regulatory domain 1, CRD1 (-358 to -211, on gsBiP6), activated expression of the BiP minimal promoter in all organs analyzed, BiP promoter activity in meristematic tissues and phloem cells required the presence of a second activating domain, CRD2 (-211 to -80). Apparently, the CRD2 sequence also harbors negative cis-acting elements, because removal of this region caused activation of gsBiP6 promoter in parenchymatic xylem rays. These results suggest that the tissue-specific control of BiP gene expression requires a complex integration of multiple cis-acting regulatory elements on the promoter.

Asunto(s)

Proteínas Portadoras/genética , Meristema/genética , Proteínas de Plantas/genética , Regiones Promotoras Genéticas/genética , Secuencias Reguladoras de Ácidos Nucleicos/genética , Proteínas de Arabidopsis , Secuencia de Bases , Secuencia Conservada/genética , ADN de Plantas/química , ADN de Plantas/genética , Retículo Endoplásmico/metabolismo , Células Eucariotas/citología , Células Eucariotas/metabolismo , Regulación de la Expresión Génica de las Plantas , Glucuronidasa/genética , Glucuronidasa/metabolismo , Datos de Secuencia Molecular , Brotes de la Planta/genética , Plantas Modificadas Genéticamente , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Alineación de Secuencia , Análisis de Secuencia de ADN , Homología de Secuencia de Ácido Nucleico , Glycine max/genética , Glycine max/metabolismo , Nicotiana/genética , Sitio de Iniciación de la Transcripción