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SymRK defines a common genetic basis for plant root endosymbioses with arbuscular mycorrhiza fungi, rhizobia , and

SymRK defines a common genetic basis for plant root endosymbioses with arbuscular mycorrhiza fungi, rhizobia , and Frankia bacteria. PNAS 2008 Volume 105 No. 12, pgs 4928-4932.

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SymRK defines a common genetic basis for plant root endosymbioses with arbuscular mycorrhiza fungi, rhizobia , and

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  1. SymRK defines a common genetic basis for plant root endosymbioses with arbuscularmycorrhiza fungi, rhizobia, and Frankia bacteria PNAS 2008 Volume 105 No. 12, pgs 4928-4932. Authors: Gherbi, H., Markmann, K., Svistoonoff, S., Estevan, J., Autran, D., Giczey, G. Auguy, F., Pe´ ret, B., Laplaze, L., Franche, C., Parniske, M., and Bogusz, D. Presented by Erick Breathwaite

  2. Endosymbiosis • Root endosymbioses are associations between plants and soil microorganisms in which microorganisms are accommodated into the host cell http://remf.dartmouth.edu/images/RootNodulesTEM/source/rootnodule_80936_5.html

  3. Importance • Endosymbioses contribute to plant nutrition and fitness worldwide therefore knowing the genetic basis for plant root symbiosis is of much importance.

  4. Types of root endosymbiosis • The three major types of root endosymbioses that occur in plants involve legumes with rhizobia bacteria, Frankia (actinomycetes) and actinorhizal plants, and arbuscularmycorrhiza (AM) fungi with plants. http://www.laspilitas.com/advanced/pictures/ceanothus_frankia.jpg

  5. Legume/Rhizobia symbiosis • Several genetic components of host symbiont interaction have been found in legumes

  6. SymRK Endre G, et al. (2002) A receptor kinase gene regulating symbiotic nodule development. Nature 417:962–966. Several downstream components of the Nod Factor signaling cascade, including the receptor kinase gene SymRKare involved in nodulation symbiosis in L. japonicusand other legume plants http://en.wikipedia.org/wiki/Lotus_japonicus

  7. Evolutionary similarity • Part of this signaling cascade is also involved in transduction of the symbiotic signal in fungi symbioses

  8. The experiment • Unlike the legume plants, the genetic components of host-symbiont interaction in actinorhiza is unknown • In this experiment, CgSymRK, a predicted SymRK gene from the actinorhizal tree C. glauca, was isolated to analyze its role in root endosymbioses http://www.hear.org/starr/plants/images/image/?q=040120-0213

  9. Isolation of CgSymRK • The C. glaucaSymRKcandidate, CgSymRK, was isolated by using a degenerate priming approachbased on similarity with legume SymRKsequences

  10. Knockdown expression of CgSymRK Table 1. Reduced nodulation in CgSymRK RNAi composite plants Nodulation was scored 12 weeks after inoculation with Frankia.

  11. ARA assays • To test the ability of CgSymRKRNAinodules to fix nitrogen via acetylene reduction activity (ARA) assays. N2 + 6e- + 6H   -->  2NH3 C2H2 + 2e-  + 2H+  --> C2H4

  12. Is CgSymRKis also involved in AM formation in C. glauca?

  13. Can CgSymRK restore nodulation and AM symbioses in a legume symrk mutant?

  14. Can CgSymRK restore nodulation and AM symbioses in a legume (L. japonicus) symrk mutant? Table 2. Complementation of Nodulation and AM formation in Lotus symrk mutants carrying CgSYMRK Nodulation was scored 4, 8, or 15 weeks after inoculation with M. loti, and AM after 3 weeks of cocultivation with G. intraradices. Results are compiled from two independent experiments.

  15. Conclusion • These results demonstrate that, in C. glaucaas in legumes, SymRKis involved in theestablishment of both nitrogen-fixing nodule and AM symbioses, thus supporting the hypothesis that signaling genes have been recruited from the more ancient AM symbiosis during the evolution of nitrogen fixing symbioses

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