Determination of the traits that determine competitive success in root colonisation and nodulation by Rhizobium leguminosarum
Lead Research Organisation:
John Innes Centre
Department Name: Molecular Microbiology
Abstract
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Technical Summary
The rhizobia are one of the best-characterised groups of plant-associated bacteria that must be able to colonise the roots of legumes before they can initiate a successful infection process, resulting in nodulation and nitrogen fixation. Colonisation of the rhizosphere by microorganisms in general is one of the primary determinant of plant productivity, yet is very poorly understood. Likewise, competition for nodulation success is poorly understood, even though legumes account for a substantial fraction of the biosphere¿s fixed nitrogen. At a practical level the use of agronomically desirable rhizobia is often limited by their lack of colonisation and nodulation competitiveness. This lack of understanding of colonisation and nodulation competitiveness is largely because it is a complex process involving multiple biotic and abiotic factors that have been difficult to examine experimentally. However, new genome based technologies such as signature tagged mutagenesis (STM), microarray analysis and biosensors allow a systematic approach to be adopted to the study of this problem. STM is particularly powerful because it allows pools of individually tagged mutants to be competed against one another and the successful strains identified by subsequent array hybridisation against the tags spotted on glass slides. Since I have developed colonisation and nodulation competition assays for R. leguminosarum strain 3841, am developing whole genome microarrays for this organism and have developed high-throughout Gfp biosensors I am well placed to use these new strategies to tackle the genuinely important problem of colonisation and nodulation competitiveness. I therefore propose to use STM first to isolate mutants of Rhizobium leguminosarum strain 3841 essential for colonisation (col) and nodulation competitiveness (noc). By starting with mutants with a clearly defined phenotype it avoids the problem of producing large amounts of transcriptome proteome data lists with no function. Next microarray analysis will be used to examine the global expression of genes in the pea rhizosphere but with a sharp focus on the expression of the col and noc genes. This will allow the examination of the environmental regulation of these genes and permit the rational design of Gfp biosensors focused on those col and noc genes that are induced in crucial microenvironments, such as root hairs and nodule infection threads. These genes have been among the most difficult to investigate, in spite of them being vitally important for root colonisation and nodulation. Gfp biosensors will allow precise spatial and temporal mapping of key col and noc gene expression, enabling their sites of action to be pinpointed. Comparative array analysis of the expression R. leguminosarum genes in the pea, alfalfa and sugarbeet rhizosphere will also be carried out to determine if there are common or discrete sets of genes induced in the rhizospheres of these plants. The induced genes will be compared to the genomes of other plant-associated bacteria to look for common colonisation genes.
Organisations
Publications
Barr M
(2008)
In vivo expression technology (IVET) selection of genes of Rhizobium leguminosarum biovar viciae A34 expressed in the rhizosphere.
in FEMS microbiology letters
Fox M
(2008)
Characterization of â??the quaternary amine transporters of Rhizobium leguminosarum bv. viciae 3841
in FEMS Microbiology Letters
Garcia-Fraile P
(2015)
Arabinose and protocatechuate catabolism genes are important for growth of Rhizobium leguminosarum biovar viciae in the pea rhizosphere.
in Plant and soil
Karunakaran R
(2009)
Transcriptomic analysis of Rhizobium leguminosarum biovar viciae in symbiosis with host plants Pisum sativum and Vicia cracca.
in Journal of bacteriology
Karunakaran R
(2010)
BacA is essential for bacteroid development in nodules of galegoid, but not phaseoloid, legumes.
in Journal of bacteriology
Oldroyd GE
(2011)
The rules of engagement in the legume-rhizobial symbiosis.
in Annual review of genetics
Poole P
(2017)
Shining a light on the dark world of plant root-microbe interactions.
in Proceedings of the National Academy of Sciences of the United States of America
Prell J
(2010)
Role of symbiotic auxotrophy in the Rhizobium-legume symbioses.
in PloS one
Prell J
(2012)
The PTS(Ntr) system globally regulates ATP-dependent transporters in Rhizobium leguminosarum.
in Molecular microbiology
Prell J
(2009)
Legumes regulate Rhizobium bacteroid development and persistence by the supply of branched-chain amino acids.
in Proceedings of the National Academy of Sciences of the United States of America
Description | Botanic Gardens seminar |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | I talked to the Botanic Gardens about nitrogen and humanity Lots of questions and feedback. This is widely advertised to the public |
Year(s) Of Engagement Activity | 2014 |
Description | Give peas a chance |
Form Of Engagement Activity | A magazine, newsletter or online publication |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Schools |
Results and Impact | We made a film with Oxford sparks on nitrogen fixation Lots os hits on the web site |
Year(s) Of Engagement Activity | 2014 |
Description | Meeting minds Oxford Alumni |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | I gave a talk to the Oxford biological sciences Alumni Enthusiastic response from the audience |
Year(s) Of Engagement Activity | 2014 |
Description | Schools one week Intensive course |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Schools |
Results and Impact | Intensive one week course for A level students in practical plant and microbial science Students all keen to apply for science based university courses |
Year(s) Of Engagement Activity | 2014 |
Description | Wymondham academy school visit |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Schools |
Results and Impact | Talk to 6th form students to encourage them to consider science as a career Students keen to apply for university places |
Year(s) Of Engagement Activity | 2014 |