Posts Tagged ‘effectors’

Effector Wisdom

January 20th, 2013

30th New Phytologist Symposium: Immunomodulation by Plant-associated Organisms

Meeting Report by Amy Huei-Yi Lee, Benjamin Petre, David L. Joly

Many organisms such as bacteria, fungi, oomycetes, nematodes and insects grow, feed and/or reproduce in close association with plant hosts. To establish such intimate interactions, symbionts (either mutualistic or parasitic) secrete effectors into host tissues, which are molecules that modulate plant cell structures and processes (Win et al., 2012a). This last decade, advances in genomics have revealed that symbionts possess dozens to hundreds of effectors. Currently, the field is moving rapidly from effector identification towards effector characterization, which provides a better understanding of how these effectors promote the establishment of a successful relationship with host plants. The 30th New Phytologist Symposium clearly illustrated this theme, as an international panel of c. 150 scientists was brought together to discuss current efforts to decipher effector functions within a wide range of biological systems. The remote location of the meeting in the Sierra Nevada mountains of California, USA, promoted lively discussions between participants during and after the sessions, but also via social networks (the whole conference was covered by a twitter feed, #30NPS tag, available onhttp://storify.com/KamounLab/30th-new-phytologist-symposium-immunomodulation-by). Read more …

Rust in the limelight

April 20th, 2012

Image by Benjamin Petre and Stephane Hacquard on the cover of the March 2012 issue of Molecular Plant Microbe Interactions. Congrats to Steph, David, Seb and coauthors for their paper: ‘A Comprehensive Analysis of Genes Encoding Small Secreted Proteins Identifies Candidate Effectors in Melampsora larici-populina (Poplar Leaf Rust)‘.

Uredinia formed by the rust fungus Melampsora larici-populina 7 days after inoculation on susceptible poplar leaves (severe and weak infection are pictured above and below the midrib, respectively). The panels below show immunofluorescence localization of small secreted proteins at the periphery of distinct infection structures in poplar leaves.

Effectors in Plant-Microbe Interactions

November 17th, 2011

Just got a copy of our book on Effectors in Plant-Microbe Interactions by Sophien Kamoun and I. It looks georgious … although the photo on the cover page is reminiscent of ‘The Eye of Sauron‘ as portrayed in Peter Jackson’s Lord of the Ringsmovie  trilogy.

Search inside this book at Amazon.com:

 

Reviews on Effectors

September 24th, 2011

Two new reviews on oomycete and fungal effectors:

both in Cellular Microbiology.

Image: Fig. 1C from Kale & Tyler: Assays for detecting pathogen-independent entry of effectors.

A Sneak Preview: ‘Effectors in Plant-Microbe Interactions’ book

September 17th, 2011

The book ‘Effectors in Plant-Microbe Interactions’

Edited by Sophien Kamoun and I, will be released by Wiley-Blackwell on January 2012:

A sneak preview …

Effectors are defined as molecules produced by bio-aggressors/pathogens/symbionts to manipulate their host plants, thereby facilitating infection (virulence or symbiotic factors, toxins, inhibitors) and/or triggering defense responses (avirulence factors, elicitors). This dual (and conflicting) activity of effectors has been broadly reported in many plant–microbial interactions. This research topic is actively investigated using a combination of approaches (genetics, molecular biology, biochemistry, physiology and developmental biology) and benefits from the recent advances in plant and microbial functional genomics and genome-wide evolutionary analyses. Tremendous progress has been made in recent years but many questions remain unanswered. The book aims to act as a catalyst for future research by bringing together a collection of contributions on plant–microbe interactions across a range of organisms (viruses, bacteria, fungi and nematodes) to identify and focus on these important questions. A book on this topic will be timely. It combines chapters by researchers involved in a diversity of plant-microbe systems that use biochemical, physiological, and developmental approaches as well as comparative genomics. Such a broad-ranging approach is providing a unique insight and a better understanding of the functions of this new class of proteins. Authors have been encouraged to discuss far reaching extensions of their current or past work and to propose cross-cutting research questions whenever possible.

Image: A great, arty photo from Sebastian Schornack (TSL) showing red fluorescent Phytophthora infestans colonizing its host. The central necrotrophic zone (in black) is surrounded by the biotrophic area (in fluo green).  The biotropic zone was caused by the action of effectors that suppressed the host responses.

 

Convergent evolution of obligate biotrophy in plant parasites

May 29th, 2011

Nearly all plants play host to a myriad of parasites. They can suffer from bacterial, viral and fungal attack, but fungal parasites are by far the most prevalent plant pathogenic organism. Over 20,000 species of fungi are parasites and cause disease in crops and plants. Parasitic fungi require a living host to survive. This forces them to achieve a delicate balance, extracting enough nutrients to ensure their own survival but not so much that they kill the plant. Common plant fungi such as powdery mildews, rusts and smuts require a living plant to sustain them.

The genomes of the hemibiotrophic (Magnaporthe oryzae, Leptopshaeria maculans, Fusarium spp., Mycosphaerella spp.) and necrotrophic (Stagnospora nodorum, Botrytis cinerea, Nectria haematoccoca), fungal plant pathogens have been released at a regular pace over the last five years and allowed a better understanding of the evolution of pathogenesis. These studies highlighted the value of comparative genomics in identifying important virulence genes with host-specific functions. Given that almost nothing is known about the molecular basis or evolution of obligate biotrophy in plant pathogens, the recent publication of papers describing the genomes of  three pathogens representing two independent evolutions of obligate biotrophy in the powdery mildews [Blumeria graminis, Spanu et al. (2010)] and the rusts [Puccinia graminis f. sp tritici & Melampsora larici-populina, Duplessis et al. (2011)] is a key step in our understanding of plant-pathogen interactions.

The genome analysis of the barley powdery mildew (Blumeria graminis) revealed a genome size expansion caused by transposon proliferation concomitant with a striking reduction in gene content, i.e., genes encoding sugar-cleaving enzymes, transporters and assimilatory enzymes for inorganic nitrate and sulfur (Spanu et al., 2010).  To identify the genetic idiosyncrasies underlying pathogenesis and biotrophic ability of rust pathogens, we have analyzed the genome sequences of the rust fungi M. larici-populina and P. graminis f. sp. tritici. in a joint collaboration between the JGI and the MIT Broad Institute (see my previous post). Our comparisons of M. larici-populina and P. graminis f. sp. tritici to other saprotrophic, pathogenic, and symbiotic basidiomycetes indicate that developmental innovations in the rust fungi lineages did not involve major changes in the ancestral repertoire of conserved proteins with known function. However, gene family expansions observed for oligopeptide transporters, auxin efflux carriers and signaling elements could reflect specific adaptations to this extreme parasitic lifestyle of these fungi. No massive gene loss was observed in M. larici-populina and P. graminis f. sp. tritici,

However, our comparisons of these three genomes with genomes from non-obligate fungal relatives have confirmed several startling commonalities amongst powdery mildews and  rusts:

  • Dramatic reduction of plant cell-wall degrading enzymes and other pathogenicity genes (i.e., evolution for “stealth”).
  • Loss of sulphite and nitrite assimilation genes (i.e., metabolic dependency on the host).
  • The massive proliferation of (retro)transposable elements which lead to significant enlargement of the overall genome size (the increase in genetic, heritable variability may confers an adaptive advantage to obligate life on a live host).
  • The deployment of large arrays of secreted effector proteins that act within and outside of host cells to counteract plant immunity and may facilitate other processes that are integral to survival within a hostile host.

Our study on the wheat and poplar rusts is the latest in a series of papers that investigates genomic attributes of biotrophy in obligate plant parasites. Another recent works focused on the oomycete Hyaloperonospora arabidopsidis, which causes downy mildew of Arabidopsis (Baxter et al., 2010). Interestingly, the genomic features discussed above were also identified  in this non-fungal lineage. Collectively, these draft genomes of these microbial parasites thus provided the first opportunity to gain insight into the genomic signatures and convergent evolution of obligate biotrophy.

A series of papers describing the transcriptome and secretome of the poplar rust will soon be published. Now, it remains to determine the role of hundreds of effector-like secreted proteins released in planta by M. larici-populina and P. graminis.

 

John McDowell’s comparison of our and Pietro’s papers appears as an invited Commentary in the PNAS early edition published online the week of May 16.

Duplessis et al. (2011) Obligate biotrophy features unraveled by the genomic analysis of rust fungi. Proc Ntl Acad Sci USA, Published online before print May 2, 2011, doi:10.1073/pnas.1019315108.

Spanu et al. (2010) Genome expansion and gene loss in powdery mildew fungi reveal tradeoffs in extreme parasitism. Science 330: 1543–1546.

Baxter et al. (2010) Signatures of adaptation to obligate biotrophy in the Hyaloperonospora arabidopsidis genome. Science 330: 1549-1551.

McDowell JM (2011) Genomes of obligate plant pathogens reveal adaptations for obligate parasitism. Proc Ntl Acad Sci USA, doi:10.1073/pnas.1105802108, published ahead of print May 16, 2011.

Photo: A poplar leaf infected by the leaf rust M. larici-populina (© F Martin).

 

I Want To Know Everything About Effectors

November 21st, 2010

NP effectors

Aphid Effectors

November 21st, 2010

Myzus persicae (10)I liked  ‘A Functional Genomics Approach Identifies Candidate Effectors from the Aphid Species Myzus persicae (Green Peach Aphid)‘ by Jorunn Bos et al.

Author Summary

“Aphids are insects that can induce feeding damage, achieve high population densities, and most importantly, transmit economically important plant diseases worldwide. To develop durable approaches to control aphids, it is critical to understand how aphids interact with plants at the molecular level. Aphid feeding induces plant defenses, which can be suppressed by aphid saliva. Thus, aphids can alter plant cellular processes to promote infestation of plants. Suppression of plant defenses is common in plant pathogens and involves secretion of effector proteins that modulate host cell processes. Evidence suggests that aphids, like plant pathogens, deliver effectors inside their host cells to promote infestation. However, the identity of these effectors and their functions remain elusive. Here, we report a novel approach based on a combination of bioinformatics and functional assays to identify candidate effectors from the aphid species Myzus persicae. Using this approach, we identified three candidate effectors that affect plant defense responses and/or aphid reproductive performance. Further characterization of these candidates promises to reveal new insights into the plant cellular processes targeted by aphids.”

Photo: The Green Peach Aphid (Myzus persicae) © www.aphidweb.com/

Parlez vous ‘Effectors’

July 19th, 2010

roc du mulinetBack Home after two weeks in the Alps and a visit to Oak Ridge National Lab in Tennessee. During my flight back to CDG, I finalized the draft of the editorial I wrote for the New Phytologist special issue dedicated to Effectors in Plant-Microbe Interactions (22nd New Phytologist Symposium, Versailles INRA Center, Paris, 13-16 September 2009). I outlined the draft when hiking along the alpine paths of the Vanoise National Park. The blooming meadows help me to find the inspiration. Here is the introduction:

[In the high valley of the Arc river in Haute Maurienne, glacier rivers and threatening seracs make loud roaring sounds, the snow is slowy retreating from the alpine meadows and hundred of plants are rushing to generate their seeds in these highlands were Winter lasts eight months.  In walking through this colorful cornocupia of flowering plants, enchanting forests of dwarf willows and rock lichens competing for light and nutrients – a peaceful struggle for life – it is hard to realize that a war is taking place in the entangled vegetal crowd.  Necrotic spots, blisters, yellow pustules are the visible testimony of the invasion of plant leaves and stem by bacterial and fungal deadly parasites …].

Photo: Roc du Mulinet – Glacier des Sources de l’Arc (Haute Maurienne, France) © F Martin

August 24th, 2009

22nps_logo

The 22nd New Phytologist Symposium entitled ‘Effectors in plant–microbe interactions’ will be held at INRA Versailles Research Centre, Paris, France from 13 to 16 September 2009. For full details about the meeting, see The New Phytologist web site.

“Effectors are defined as molecules produced by bio-aggressors/pathogens/symbionts to manipulate their host plants, thereby facilitating infection (virulence or symbiotic factors, toxins, inhibitors) and/or triggering defense responses (avirulence factors, elicitors). This dual (and conflicting) activity of effectors has been broadly reported in many plant–microbial interactions. This research topic is actively investigated using a combination of approaches and benefits from the recent advances in plant and microbial functional genomics and genome-wide evolutionary analyses. The 22nd New Phytologist Symposium aims to bring together scientists working on plant–microbe interactions across a range of organisms (viruses, bacteria, fungi and nematodes) to identify and focus on these important questions.” from H. Slater.