Relationship between in vitro enhanced nitrogenase activity of an Azospirillum brasilense Sp7 mutant and its growth-promoting activities in situ.
In this work, we further analyzed an Azospirillum brasilense Sp7 mutant (Sp7::Tn5-33) showing a pleiotrophic phenotype due to a Tn5 insertion into an open reading frame of 840 bp (orf280). The deduced amino acid sequence of this region has high similarity to a family of universal stress proteins. Because the most interesting property exhibited by the Sp7::Tn5-33 mutant was an enhanced in vitro nitrogen fixation activity, we addressed the question of whether it could benefit the host plant. We found that the increased nitrogenase activity at the free-living state of the mutant bacterium was correlated with an increased production of the nitrogenase reductase protein (NifH), in amounts approximately 1.5 times higher than the wild type. The mutant strain exhibited the same level of auxin production and the same colonization pattern of wheat roots as the wild type. We also observed that Sp7::Tn5-33 increased the total plant dry weight, although the N content did not differ significantly between wheat plants inoculated with mutant or wild-type strains.
de Campos
Samanta Bolzan
SB
Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, CP, Brazil.
Roesch
Luiz Fernando Wurdig
LF
Zanettini
Maria Helena Bodanese
MH
Passaglia
Luciane Maria Pereira
LM
D015806:Azospirillum brasilense / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005966:Glucuronidase / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009586:Nitrogen Fixation / Q000235:genetics / Q000502:physiology; D009591:Nitrogenase / Q000235:genetics / Q000378:metabolism*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D013997:Time Factors; D014908:Triticum / Q000378:metabolism / Q000382:microbiology
D001426:Bacterial Proteins; D007210:Indoleacetic Acids; D010088:Oxidoreductases; D009591:Nitrogenase; C029130:nitrogenase reductase; D005966:Glucuronidase