Goldacre paper: Auxin: at the root of nodule development?

Ulrike Mathesius

doi:10.1071/FP08177

RESEARCH ARTICLE

Previous Next Contents Vol 35(8)

Goldacre paper: Auxin: at the root of nodule development?

Ulrike Mathesius

+ Author Affiliations

- Author Affiliations

^A School of Biochemistry and Molecular Biology, Australian National University and Australian Research Council Centre of Excellence for Integrative Legume Research, Linnaeus Way, Canberra, ACT 0200, Australia. Email: ulrike.mathesius@anu.edu.au

^B This paper originates from the Peter Goldacre Award 2007 of the Australian Society of Plant Scientists, received by the author.

Functional Plant Biology 35(8) 651-668 https://doi.org/10.1071/FP08177
Submitted: 24 June 2008 Accepted: 14 August 2008 Published: 19 September 2008

Abstract

Root nodules are formed as a result of an orchestrated exchange of chemical signals between symbiotic nitrogen fixing bacteria and certain plants. In plants that form nodules in symbiosis with actinorhizal bacteria, nodules are derived from lateral roots. In most legumes, nodules are formed de novo from pericycle and cortical cells that are re-stimulated for division and differentiation by rhizobia. The ability of plants to nodulate has only evolved recently and it has, therefore, been suggested that nodule development is likely to have co-opted existing mechanisms for development and differentiation from lateral root formation. Auxin is an important regulator of cell division and differentiation, and changes in auxin accumulation and transport are essential for lateral root development. There is growing evidence that rhizobia alter the root auxin balance as a prerequisite for nodule formation, and that nodule numbers are regulated by shoot-to-root auxin transport. Whereas auxin requirements appear to be similar for lateral root and nodule primordium activation and organ differentiation, the major difference between the two developmental programs lies in the specification of founder cells. It is suggested that differing ratios of auxin and cytokinin are likely to specify the precursors of the different root organs.

Additional keywords: actinomycetes, auxin transport, cytokinin, flavonoids, lateral root, rhizobia, symbiosis.

Acknowledgements

I am grateful for the encouragement, discussion and collaboration of past and present laboratory members and colleagues involved in the presented research, in particular Giel van Noorden, Anton Wasson, Flavia Pellerone, Karsten Oelkers, Joko Prayitno, Tursun Kerim, Melinda Aprelia, Robert Wiblin, Alexander Ivakov, Julia Frugoli, Brett Ferguson, John Ross, Jim Reid, Peter Gresshoff, Christine Beveridge, Michael Djordjevic and Barry Rolfe. I would also like to thank the reviewers for many constructive comments and the Australian Research Council for funding through an Australian Research Fellowship (DP0557692) and through the ARC Centre of Excellence for Integrative Legume Research (CE0348212). A special ‘thank you’ to the Australian Society of Plant Scientists and Functional Plant Biology for their encouragement through the Goldacre award.

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