• Nick Brewin's Research

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Curriculum Vitae

• 1969 BSc, University of Cambridge
• 1973 PhD, University of Cambridge
• 1973 Beit Postdoctoral Fellow, ICRF, London
• 1976 - 2006 Project Leader, John Innes Centre
• 1999 - 2006 Chair of JIC Graduate Studies Committee
• 2001 ScD, University of Cambridge
• 2002 - present Honorary Professor, University of East Anglia
• 2003 MBA, Open University
• 2005 - 2008 Member of BBSRC Studentships & Fellowships Panel
• 2006 - present Emeritus Fellow

Nick Brewin

John Innes Emeritus Fellow

Molecular Microbiology

Contact details

nick.brewin@bbsrc.ac.uk

Research interests

Molecular biology of the Rhizobium-legume symbiosis:

Symbiotic nitrogen fixation through the Rhizobium-legume symbiosis is an important and sustainable input into agricultural systems worldwide. But what makes legumes special? Tissue and cell invasion by Rhizobium is closely associated with the targetted secretion of a legume-specific glycoprotein that we have termed AGP-Extensin.

Legume AGP-extensins and the propagation of infection threads

Infection threads are tubular transcellular structures that serve as the conduit for cell and tissue invasion by Rhizobium. Orientation of apical growth of an infection thread exploits the polarized cytoskeletal network that is established following challenge of host cells with Nod-factor. At the apex of the infection thread there is targeted secretion of AGP-extensins. (AGPEs are a legume-specific class of highly glycosylated glycoprotein co-polymer). The conserved 3’-UTR of AGPE contains numerous repeats of a UUGU motif, suggesting binding of Pumilio-like Puf-proteins. In budding yeast and Drosophila embryos, Puf-proteins are associated with “locasome”-type ribonucleoprotein particles that mobilize particular RNAs along the polarized actin cytoskeleton, allowing protein translation only when these transcripts reach their destination within the polarized cell.

A similar process could control the polarized growth of infection threads. In the lumen of the infection thread, it is proposed that peroxide-driven cross-linking of AGPEs (and other plant glycoproteins and polysaccharides) can modify the rigidity of the infection thread wall and the fluidity of the infection thread matrix. The observed distribution of peroxide in growing infection threads correlates with that of plant diamine oxidase, indicating that this enzyme may generate peroxide from degradation of polyamines. Furthermore, it is possible that these polyamines are derived from rhizobial cells, thus providing an auto-regulated system for the control of infection thread growth. The use of molecular probes to analyse cell wall components in symbiotically defective mutant lines of pea and Medicago can help to reveal the morphological phenotypes of abnormal infection threads, infection droplets and symbiosomes.