Poster: Plant-symbiont interactions
Abs #
587: Cloning and identification of genes involved in plant growth promotion by a Burkholderia species (PsJN)
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Presenter: |
Wang, Keri , wangkeri@agr.gc.ca |
Authors | Wang, Keri (A) Conn, Kenneth (A) Lazarovits, George (A) | | Affiliations: |
(A): Southern Crop Protection and Food Research Center
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The genus Burkholderia is a major group among the rhizobacteria that increase crop yield, and provide biological control of soil-borne diseases. However, genetic characterization of plant growth promotion in this group is not well understood. In this study, we examined the genes involved in growth promotion of potato by a Burkholderia sp (PsJN) that stimulates plant root growth under gnotobiotic conditions by 6 to 10 times compared to uninoculated controls. Tn5 transposon mutagenesis was used to create non-growth promoting mutants of PsJN. One of 2,400 Tn5 mutants, H41, showed the same ability to colonize the potato plants as the strain PsJN, but was devoid of growth-promotion activity. The interrupted gene in PsJN was identified from a lambda library by subcloning and complementation tests. Cloning and sequencing of the DNA at the Tn5 insertion site revealed a 7.2-kb region containing four full open reading frames (ORFs), three of them are putative genes conferring in vivo biosynthesis of one product, but not phytohormones such as indole-3-acetic acid etc., and potentially involved in plant growth promotion. The ORF1 and ORF2 are linked together and share the same promoter while ORF3 is located in downstream of ORF2. The proteins encoded by these genes were functionally expressed in E. coli, extracted, purified and characterized. The product of this enzymatic pathway was demonstrated to restore growth promotion of the mutant H41 when supplemented into the tissue culture medium. We concluded that the identified genes ORF1-3 were involved in plant growth promotion activities but we surmise that there are more genes controlling growth promotion. Several other mutants are now being examined for the basis of their loss of growth promotion.
