Genetic differences between Bradyrhizobium japonicum variant strains contrasting in N(2)-fixation efficiency revealed by representational difference analysis.
Two variant strains of Bradyrhizobium japonicum, derived from SEMIA 566, adapted to the stressful environmental conditions of the Brazilian Cerrados and characterized by contrasting capacities for N(2) fixation, were compared by representational difference analysis (RDA). Twenty-four gene sequences that are unique to the highly effective strain S 370 were identified, eight showing high similarity to known genes, nine encoding putative proteins and seven representing conserved hypothetical or hypothetical proteins; they were classified in eight functional categories. Among those genes, some were highlighted for their known or potential functions in plant-microbe interactions. The nodulation outer protein P (nopP), related to the type-III secretion system (TTSS) and a major determinant of nodulation of some tropical legumes, was detected in the genome of strain S 370. Three coding sequences (CDS) identified by RDA were expressed in proteomics experiments with B. japonicum strain USDA 110 (ChvE and NopP). The use of the sequences identified by RDA in the highly effective strain S 370 might represent an important tool to speed up strain selection programs, accelerating pre-screening procedures. Additionally, the conserved hypothetical and hypothetical proteins identified in strain S 370 might encode important but still unknown proteins related to the symbiosis that deserve further study.
Laboratório de Biotecnologia dos Solos, Embrapa Soja, Cx. Postal 231, Londrina, 86001-970, PR, Brazil, fgbarcel@yahoo.com.br
Fernando Gomes
FG
Barcellos
Jesiane Stefânia da Silva
JS
Batista
Pâmela
P
Menna
Mariangela
M
Hungria
D000596:Amino Acids / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D020369:Bradyrhizobium / Q000235:genetics* / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D014644:Genetic Variation; D008969:Molecular Sequence Data; D009154:Mutation; D009586:Nitrogen Fixation
D000596:Amino Acids; D001426:Bacterial Proteins; D005227:Fatty Acids