THE ASPARAGINE SYNTHETASE GENE VFAS1 IS STRONGLY EXPRESSED IN THE NITROGEN-FIXING ZONE OF BROAD BEAN (VICIA-FABA L) ROOT-NODULES

A full-length transcript sequence encoding the broad bean (Vicia faba L.) asparagine synthetase (AS) VfAS1 was isolated from a nodule cDNA l ibrary. Sequence homologies indicated that VfAS1 belonged to the gluta mine-dependent type of AS enzymes. The corresponding gene was highly e xpressed in root nodules and at a three-fold lower level in uninfected roots. Additionally, traces of VfAS1 transcripts were detected in epi cotyl and stem tissues. Tissue-print hybridizations revealed that the VfAS1 gene was strongly expressed in the nitrogen-fixing zone III of r oot nodules. VfAS1 transcripts were absent from the meristem, the pref ixing zone IE as well as from peripheral nodule tissues. (C) 1997 Else vier Science Ireland Ltd.