title: Uptake Hydrogenase (Hup) in Common Bean (Phaseolus vulgaris) Symbioses.
abstract: Strains of Rhizobium forming nitrogen-fixing symbioses with common bean were systematically examined for the presence of the uptake hydrogenase (hup) structural genes and expression of uptake hydrogenase (Hup) activity. DNA with homology to the hup structural genes of Bradyrhizobium japonicum was present in 100 of 248 strains examined. EcoRI fragments with molecular sizes of approximately 20.0 and 2.2 kb hybridized with an internal SacI fragment, which contains part of both bradyrhizobial hup structural genes. The DNA with homology to the hup genes was located on pSym of one of the bean rhizobia. Hup activity was observed in bean symbioses with 13 of 30 strains containing DNA homologous with the hup structural genes. However, the Hup activity was not sufficient to eliminate hydrogen evolution from the nodules. Varying the host plant with two of the Hup strains indicated that expression of Hup activity was host regulated, as has been reported with soybean, pea, and cowpea strains.
authors.affiliation: Centro de Energia Nuclear na Agricultura, Universidade de Sao Paulo, Campus Piracicaba, 13400 Piracicaba, Sao Paulo, Brazil; Biological Nitrogen Fixation Laboratory, Department of Agronomy and Soils, University of Puerto Rico, Mayagüez, Puerto Rico 00681 ; and Soybean and Alfalfa Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, HH-19, Building 011, BARC-West, Beltsville, Maryland 20705.
authors.forename: R B
authors.initials: RB
authors.lastname: Navarro
authors.forename: A A
authors.initials: AA
authors.lastname: Vargas
authors.forename: E C
authors.initials: EC
authors.lastname: Schröder
authors.forename: P
authors.initials: P
authors.lastname: van Berkum