Genetic approaches for studying rhizosphere colonization

Lam, Stephen; Ellis, D M; Ligón, James M.

doi:10.1007/978-94-011-3336-4_5

Cited by 16 publications

(2 citation statements)

References 19 publications

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“…1). In analogous studies using E. coli lacZ as indicator gene, Lam et al (1990) and van Overbeek and van Elsas (1995) identified plant exudateresponsive promoter probe fusions at frequencies of 5 x lop3 (50110000) and 3 x lop3 (411400), respectively. The fact that we identified only one such mutant among 10 290 insertions (frequency approximately is consistent with the more stringent requirements that must be met for the expression of PhoA activity.…”

Section: Discussionmentioning

confidence: 96%

“…Promoter probe techniques are being exploited to identify rhizosphere constituents that elicit the expression of bacterial genes previously implicated in plant-microbe interactions (e.g., Phillips and Streit 1996), to identify promoters whose transcription can indicate conditions of nutrient supply or limitation prevailing in the rhizosphere (e.g., Kragelund et al 1995), and to detect previously unidentified genes, relevant to the plant -microbe interaction, whose expression is induced by plant exudate constituents (e.g., Lam et al 1990;van Overbeek and van Elsas 1995). For this study, TnphoA was selected as both promoter probe and protein localization indicator in an effort to selectively identify exudate-inducible genes encoding cell surface constituents pertinent to the P. putida GR12-2 -canola interaction.…”

Section: Discussionmentioning

confidence: 99%

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Bacterial genetic loci implicated in thePseudomonas putidaGR12-2R3 – canola mutualism: identification of an exudate-inducible sugar transporter

Bayliss

Bent²,

De³

et al. 1997

Can. J. Microbiol.

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Pseudomonas putida GR12-2R3 promotes the emergence and growth of diverse plant species. Analyses of TnphoA insertion mutations are revealing bacterial characteristics pertinent to the plant-microbe interaction. Pseudomonas putida PG269 is a TnphoA insertion derivative of GR12-2R3 that expresses canola seed exudate-inducible alkaline phosphatase (PhoA) activity. It promoted the growth of canola roots, as well as strain GR12-2R3, and outgrew its parent when they were cocultured in the presence of canola roots or in liquid seed exudate medium. (In contrast, mutant PG126 failed to promote canola root growth and was outgrown by its parent strain.) The PhoA activity of strain PG269 was induced by glucosamine and other sugars; glucosamine inhibited the growth of strain GR12-2R3 and stimulated the growth of strain PG269. Strain PG269 contained two TnphoA insertions: seiA1::TnphoA and seiB1::TnphoA. Strain PG312, which contained only insertion seiA1::TnphoA, shared all aspects of the PG269 phenotype, except the ability to outcompete strain GR12-2R3 during coculture. Insertion seiA1::TnphoA interrupted an open reading frame related in sequence to members of the MalF family of sugar transporter subunits. The PhoA-inducing fraction of canola seed exudate was hydrophilic, low in molecular weight, and heat stable. It cochromatographed with basic amino acids and amino sugars, and was inactivated by strains GR12-2R3 and PG269. Gene seiA may encode a subunit of an ABC transporter with broad specificity for glucose and related sugars whose expression can be induced by exudate sugars.

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Section: Discussionmentioning

confidence: 96%