The promoter of the Vicia faba L. gene VfEnod12 encoding an early nodulin is active in cortical cells and nodule primordia of transgenic hairy roots of Vicia hirsuta as well as in the prefixing zone II of mature transgenic V-hirsuta root nodules

A full-length cDNA encoding the Vicia faba L. early nodulin VfEnod12 was is olated. The deduced protein sequence specified a 90 amino acid protein with a MW of 10 206 and contained a putative signal peptide sequence followed b y PPX3 repeats characteristic of Enod12 proteins. The VfEnod12 gene was fou nd to be expressed specifically in root nodules as early as 3 days post ino culation with Rhizobium leguminosarum bv. viciae. In mature nodules, VfEnod 12 transcripts were confined to the prefixing zone II. A 3.3 kb genomic fra gment carrying the complete VfEnod12 coding region was isolated. No interve ning sequences were identified in the coding region. A promoter fragment ca rrying the -692/-41 region mediated reporter gene expression in root cortic al cells, module primordia and the prefixing zone II of transgenic Vicia hi rsuta root nodules. This fragment contained a putative binding site for the transcription factor ENBP1. In contrast to the highly conserved terminal A ATAA motif of the ENBP1 binding site of known Enod12 promoters, the VfEnod1 2 promoter was characterized by an altered terminal AATAT sequence. This al teration did not interfere with VfEnod12 promoter activity in transgenic ro ots and nodules of V. hirsuta. (C) 2000 Elsevier Science Ireland Ltd. All r ights reserved.