Effector-triggered defence: A new concept in plant pathogen defence

In June, a team of Brassica researchers from the University of Hertfordshire proposed a new classification for a type of plant defence mechanism: effector-triggered defence (ETD).

Henrik Stotz is first author of the paper describing ETD, currently In Press in Trends in Plant Science. He explains, “In the same way that humans have developed immune responses against human disease pathogens, crops can be bred for resistance against disease pathogens, but we need to improve our understanding of effective resistance mechanisms within plants. Our research enhances the traditional understanding of the plant defence system and describes a new concept, which is how plants protect themselves against the pathogens that grow in the space outside plant cells (the apoplast) – a new concept called effector-triggered defence or ETD.”

Traditionally, plant pathogen defence is broken into two broad forms: pathogen-triggered immunity (PTI) and effector-triggered immunity (ETI). PTI is the first action the plant takes against a pathogen and is triggered when the pathogen lands on the plant. The pathogen releases molecules called effectors into the plant cells, which the plant recognises and reacts against. If the effectors are not recognised, the pathogen can spread with little resistance.

The team from Hertfordshire, led by Bruce Fitt, argue that one line of defence, R gene-mediated host resistance against fungal pathogens that grow in the space between cells, is not adequately explained by either mechanism.

Effector-triggered defence (ETD) is mediated by R genes encoding cell surface-bound receptor-like proteins that engage the receptor-like kinase SOBIR1 – an extracellular recognition. The response is host cell death after an extended period of endophytic pathogen growth. This is in contrast to ETI, in which detection of the pathogen occurs within cells and usually triggers fast host cell death.

ETD is described in Stotz et al. (In Press) Trends in Plant Science DOI: http://dx.doi.org/10.1016/j.tplants.2014.04.009

The quotes used in this article are from this BBSRC Press Release. This story was originally posted on the UK Brassica Research Community website.


Plant Doctors at the Big Bang Fair

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Published on: March 19, 2014

BigBang cover2

On Friday I went to the NEC in Birmingham to join an intrepid team of plant scientists running activities on an exhibit at the free national science, technology and engineering event the Big Bang Fair. The stand was organised and funded by the British Society of Plant Pathology and the John Innes Centre.

The theme of the exhibit was Plant Doctors. Visitors learned about plant diseases and were encouraged to think about a world without plant doctors – what effects would uncontrolled plant diseases have on our air quality and food supply?

There were four activities on the stand, aimed at different age groups.

The main event was the Plant Doctors activity, where children and young people could don a white coat and clipboard and learn to diagnose a bacterial, fungal or viral plant disease. In my experience the particularly gruesome crown gall tumour (just like the black death!) went down well, but some groups were fascinated by the spores on the bean rust pustules (little mushrooms), which we showed them down the microscope.

At the Polling Station, adults and young people discussed the benefits and drawbacks of bio-control, pesticides and GM approaches to controlling plant pathogens. Older Plant Doctors were also invited to vote on how best to treat the plant diseases. I didn’t spend much time on this activity, but it seemed to keep some groups very engaged. It was certainly an effective way of talking about the importance of innovation in plant science. (more…)

Plant science, by JoVE!

JoVE 2

Researchers from the University of Warwick published a methodology paper with a twist this week. The paper, published online by the Journal of Visualized Experiments (JoVE), gives step-by-step instructions and video demonstration of a method for purifying a protein and identifying proteins that perform its post-translational modifications.

Authors Sophie Piquerez, Alexi Balmuth, Jan Skenář, Alex JonesJohn Rathjen and Vardis Ntoukakis developed the method in order to characterize the interactions between nucleotide-binding leucine-rich-repeat proteins and the Prf/Pto complex in effector-triggered immunity. In principle the method could be applied to any protein – the protein of interest is epitope-tagged, immunoprecipitated and analysed by MS.

A video journal lends itself to new or improved methodology rather than high impact conclusions. As with a lot of JoVE articles, the scientifically significant results obtained using the protocol have already been published; in this case in Ntoukakis et al. 2013 (PLOS Pathogens, 10.1371/journal.ppat.1003123).

The authors conclude the abstract by saying the paper demonstrates:

  1. Dynamic changes in PTMs such as phosphorylation can be detected by mass spectrometry;
  2. It is important to have sufficient quantities of the protein of interest, and this can compensate for the lack of purity of the immunoprecipitate;
  3. The immunoprecipitation step is essential to get enough protein to do the MS. (more…)

AHDB Crop Research Conference: Knowing your enemy

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Published on: October 9, 2013

GARNet Research and Engagement Officer Lisa Martin reports on the AHDB Crop Research Conference.

On 25 September, I hopped on the train down to London to attend the Agriculture and Horticulture Development Board (AHDB)’s Crop Research Conference. This event set out to bring together researchers and the agricultural industry “to take the latest research out of the laboratory and into the field”. The theme for the day was “Knowing your enemy – the future of crop protection” and speakers were divided into three categories.

In ‘Advances in Genomics’ we heard from Lin Field from Rothamsted Research, who spoke about her work in insect genomics. Paul Birch from the James Hutton Institute also provided insights into Phytophthera pathogenomics and disease resistance, while Rick Mumford from the Food and Environment Research Agency (FERA) spoke on the subject of advances in plant diagnostics.

In particular, Dr Mumford highlighted the recent development of Loop-mediated isothermal AMPlification (LAMP) technology; a rapid, field-based diagnostic method of DNA amplification that has the ability to produce conclusive test results in as little as 10–15 minutes, and provides improvements over traditional PCR methods. He also spoke about how next generation sequencing (NGS) is being used to identify new plant viruses, especially a recent breakthrough in identifying a novel virus responsible for internal carrot browning.

On to ‘Population and Evolutionary Biology’. In this section, John Lucas from Rothamsted Research gave an update on the evolution of fungicide resistance, while Paul Nicholson from the John Innes Centre spoke on the subject of wheat resistance to Fusarium head blight. Rothamsted’s Stephen Parnell also gave a very interesting talk on how mathematical modelling can help predict the spread of pests and diseases through early warning surveillance.

Also in this section was a presentation by Paul Neve from the University of Warwick’s Crop Centre, which was on the subject of herbicide resistance in weeds. Dr Neve explained that low rate herbicide application allows for the selection of hereditary resistance traits in weeds, and once that resistance is endemic, it can have devastating effects. To this end, Dr Neve’s work mostly focuses on understanding the evolutionary processes that lead to resistance, as this, he believes, is the key to combating the outcomes of resistance.

L-R: Allan Downie, Jurriaan Ton, Alison Karley and panel Chair Keith Norman from Velcourt Ltd. Photo by Lisa Martin.

Lastly, after lunch, it was time for some ‘Lessons from Ecology’ and here presentations were given by Alison Karley, an agroecologist from the James Hutton Institute who works on optimising biocontrol; Jurriaan Ton from the University of Sheffield who brought us up to speed with recent advances in understanding and manipulating plant immunity; and finally Allan Downie from the John Innes Centre and co-ordinator of the Nornex consortium of scientists working on Ash Dieback disease.

A champion of open access, Professor Downie declared that “open access data will revolutionise science” and highlighted the ways in which crowdsourcing and citizen science are being used to understand Ash Dieback. These methods include the Facebook game Fraxinus that has allowed members of the public to help increase understanding of the Hymenoscyphus pseudoalbidus (a.k.a. Chalara fraxinea) genome, and the open access website OpenAshDieback, to which scientists are being encouraged to contribute data analysis and knowledge in the hope of, ultimately, limiting the impact of Ash Dieback.

To end on a high note over wine and canapés, the Science Minister David Willetts had been invited to present awards to the winners of a PhD student poster competition. The deserving winner was Rachel Goddard from John Innes Centre whose work on finding alternative semi-dwarfing genes that confer yield benefits to crop plants without compromising plant immunity caught the judges’ eyes. Congratulations, Rachel!

I live-tweeted throughout the conference, so please check out @GARNetweets for more insights, or search Twitter for #AHDBconf. You can also find the poster and speaker abstracts, and the speaker presentations, on the HGCA website here, and photos of the event are here.

Reports from ICAR 2013 – Sarah Harvey

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Published on: August 12, 2013

Sarah Harvey, from the Beynon Group at the University of Warwick, brings us our final report from ICAR 2013.

I am a final year PhD student working in Professor Jim Beynon’s group at the University of Warwick. Our group focuses on the interactions of Arabidopsis with the oomycete pathogen Hyaloperonospora arabidopsidis, a natural model system used for the molecular study of host-pathogen interactions. My project focuses on one effector protein identified from this pathogen and it’s molecular function within the host plant, including direct protein interactions and biochemical function, as well as transcriptional impacts on the host plant.

I was lucky enough to receive funding from the Gatsby Charitable Foundation through GARNet, and also from SEB and the Company of Biologists, which allowed me to attend The 24th International Conference on Arabidopsis Research (ICAR) in Sydney, June 2013. The conference is the world’s leading conference on Arabidopsis research and attracts many prominent researchers in the field as well as covering many areas of Arabidopsis research, for example biotic and abiotic stresses, epigenetics and hormones which were particularly interesting to me. (more…)

Ash Dieback News

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Published on: February 21, 2013


This video is an introduction to a series of filmed talks from the Forestry Commission Plant Health Conference. It introduces the ash dieback problem nicely and places it in a wider context. A number of experts give their opinions on how to approach combatting the disease.

Another new tree health resource is the UKPSF’s Ash Dieback web resource, which was launched this week. Mimi Tanimoto, Executive Officer of the UKPSF, said, “Speaking to scientists who wanted to do something to help combat ash dieback, I found a recurring problem that they were unsure of what else was happening. It was clear that by joining up the various projects we could better tackle the disease.” The website will be updated regularly with news, and it is possible to sign up on the site to receive these updates via email. Anyone who has news that they would like added to the site can contact Mimi at mimitanimoto@societyofbiology.org.

The final piece of ash dieback news is that the Open Ash Dieback project, which crowdsources genome analysis of ash trees and the fungal pathogen Chalara fraxinea,published their first paper last week. Crowdsourcing genomic analyses of ash and ash dieback – power to the people by researchers from several UK universities, lead by two groups at the Sainsbury Laboratory, was published in GigaScience 2:2 doi:10.1186/2047-217X-2-2.

Ash trees and human health

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Published on: January 24, 2013
A lone ash tree in Worcestershire

I have to admit that as a plant scientist plugged into the major social media networks that when I was inundated with articles and posts about ash dieback (Chalara fraxineai) in December, I got a bit fed up with it. Of course I appreciate all species have intrinsic value and it will be sad if Britain loses its ash trees – but I have no emotional attachment to ash trees, and pathogens are a fact of life. British countryside is managed land, so with effective management other trees will fill the gaps. However, a paper published in the February issue of American Journal of Preventive Medicine (Donovan et al., 2013) suggests the health effects on humans of losing trees are significant, and that serious loss of ash trees in the UK could have consequences beyond the financial burden on the forestry industry and the short-term loss of trees. 

Adult emerald ash borer on a penny

The research paper is an analysis of the effects of emerald ash borer (Agrilus planipennis) damage to North American ash trees. Emerald ash borer is a green beetle native to Asia, and was introduced to North America in 2002. It causes significant damage to all North American ash species and an infestation can kill a mature tree within four years. For this study, Donovan et al. looked at human mortality data from 1296 counties across the 15 states where there were confirmed emerald ash borer infestations in 2010. (more…)

Plant disease resistance with Eric Holub

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Published on: January 11, 2013

Here, Eric Holub from the University of Warwick describes his research on the genetics of disease resistance mechanisms as well as a bit about life in academic research in the UK. He explains the real-world application of his research on the model plant Arabidopsis thaliana by saying, “If the plant can control its own diseases, chemical control will be be much less required.”

This is the third video podcast taken at the UK PlantSci conference in 2012. See the previous ones with John Runions and Katherine Denby here and here. To register for UK PlantSci 2013, go to the website.


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