Prof Allan Downie

Emeritus Fellow
Molecular Microbiology

I am interested in understanding the interactions that occur when plants interact with micro-organisms. For years I have analysed the molecular signalling that occurs during establishment of rhizobial-legume symbioses.

More recently I have become involved in understanding the pathogenic interaction that occurs when ash trees are infected by the ash dieback fungus.

In recent years my work on rhizobial-legume interactions has focussed on two main areas, rhizobial attachment to roots and the subsequent signalling events that promote the initiation of plant-made infection structures that enable rhizobia to infect roots, leading to the development of nitrogen-fixing nodules. Rhizobial surface polysaccharides and secreted proteins are required for attachment to root hairs. Attached rhizobia secrete nodulation signalling molecules called Nod factors and these induce two calcium-based signalling pathways, one involving an influx of calcium across root-hair membranes and the other is an oscillation of calcium within and around the nucleus. It appears that both pathways are required to stimulate the formation of ‘infection threads’ plant-made structures that allow the rhizobia to infect roots and ultimately form nitrogen-fixing nodules. Associated with infection initiation is localised degradation of the plant cell wall.

More recently I have been coordinating a research network (called Nornex) aiming at a molecular understanding of ash dieback caused by the fungus Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea). This involves eleven partner research institutions aiming to understand the basis for pathogenicity in the fungus and analysing the potential of genetically determined inheritance of resistance in ash trees.

Genome sequence data and its analyses are posted on an open-access website.     

Professor Allan Downie awarded Adam Kondorosi prize for Plant Sciences

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The fight against ash dieback strides on thanks to international collaborations and open access data from the Nornex consortium

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Genome sequence for mother of ash dieback survival

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First close up images of Chalara fraxinea growing on the leaf stem of infected ash

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Selected Publications

Oldroyd G. E., Murray J. D., Poole P. S., Downie J. A. (2011)

The rules of engagement in the legume-rhizobial symbiosis

Annual Review of Genetics 45 p119-144

Publisher’s version: 10.1146/annurev-genet-110410-132549

Edwards A., Frederix M., Wisniewski-Dyé F., Jones J., Zorreguieta A., Downie J. A. (2009)

The cin and rai quorum-sensing regulatory systems in Rhizobium leguminosarum are coordinated by ExpR and CinS, a small regulatory protein coexpressed with CinI.

Journal of Bacteriology 191 p3059-3067

Publisher’s version: 10.1128/JB.01650-08

Oldroyd G. E., Downie J. A. (2008)

Coordinating nodule morphogenesis with rhizobial infection in legumes.

Annual Review of Plant Biology 59 p519-546

Publisher’s version: 10.1146/annurev.arplant.59.032607.092839

Recent Publications

McMullan M., Rafiqi M., Kaithakottil G., Clavijo B. J., Bilham L., Orton E., Percival-Alwyn L., Ward B. J., Edwards A., Saunders D. G. O., Garcia Accinelli G., Wright J., Verweij W., Koutsovoulos G., Yoshida K., Hosoya T., Williamson L., Jennings P., Ioos R., Husson C., Hietala A. M., Vivian-Smith A., Solheim H., MaClean D., Fosker C., Hall N., Brown J. K. M., Swarbreck D., Blaxter M., Downie J. A., Clark M. D. (2018)

The ash dieback invasion of Europe was founded by two genetically divergent individuals.

Nature ecology & evolution

Publisher’s version: 10.1038/s41559-018-0548-9

Downie J. A. (2017)

Ash dieback epidemic in Europe: How can molecular technologies help?

PLoS Pathogens 13 pe1006381

Publisher’s version: 10.1371/journal.ppat.1006381

Hood G., Ramachandran V., East A. K., Downie J. A., Poole P. S. (2017)

Manganese transport is essential for N2-fixation by Rhizobium leguminosarum in bacteroids from galegoid but not phaseoloid nodules.

Environmental Microbiology 19 p2715-2726

Publisher’s version: 10.1111/1462-2920.13773

Roy S., Robson F., Lilley J., Liu C. W., Cheng X., Wen J., Walker S., Sun J., Cousins D., Bone C., Bennett M. J., Downie J. A., Swarup R., Oldroyd G., Murray J. D. (2017)

MtLAX2, a Functional Homologue of the Arabidopsis Auxin Influx Transporter AUX1, Is Required for Nodule Organogenesis.

Plant Physiology 174 p326-338

Publisher’s version: 10.1104/pp.16.01473

Pini F., East A. K., Appia-Ayme C., Tomek J., Karunakaran R., Mendoza-Suarez M., Edwards A., Terpolilli J., Rowoth J., Downie J. A., Poole P. (2017)

Lux bacterial biosensors for in vivo spatiotemporal mapping of root secretion.

Plant Physiology DOI:10.1104/pp.16.01302 pDOI:10.1104/pp.16.01302

Publisher’s version: 10.1104/pp.16.01302

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