PLANT PHYSIOLOGY , Vol 115, Issue 4 1307-1317, Copyright © 1997 by American Society of Plant Biologists
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GENE REGULATION AND MOLECULAR GENETICS |
Characterization of the Common Bean Uricase II and Its Expression in Organs Other than Nodules
N. Capote-Mainez and F. Sanchez
Departamento de Biologia Molecular de Plantas, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Cuernavaca, Morelos CP 62210, Mexico
Uricase II is a purine metabolic enzyme highly induced in root nodules
during the symbiosis established between legumes and bacteria of the genera
Rhizobium and Bradyrhizobium. Here we describe the characterization of bean
(Phaseolus vulgaris) nodule uricase II cDNA and show that uricase II is
encoded by a single gene in the bean genome. This gene is also expressed in
cotyledons, roots, and hypocotyls during bean seedling establishment, and
an anti-uricase antibody recognizes the protein in different seedling
organs. Uricase II has also been found in Leucaena leucocephala seedlings,
suggesting that it participates during seedling establishment in legumes
that do not transport ureides. A 50-kD polypeptide that is detected by the
anti-uricase antibody is found in cotyledons during seedling development.
This higher-molecular-mass form is also detected in developing roots and
hypocotyls but not in nodules. In situ hybridization experiments in root
seedlings showed uricase II transcripts in the metaxylem parenchyma cells
and phloem fibers of the vascular system.
