Posts Tagged ‘plant-microbe interactions’

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 …

Biocomplexity of Plant-Fungal Interactions

February 7th, 2012

The book ‘Biocomplexity of Plant-Fungal Interactions‘ edited by Darlene Southworth (Southern Oregon University) has been published. The target audience is botanists who may not have considered the roles that close contacts with fungi play in the life of plants—at the level of the individual or the community. The chapters promote ideas that tell the reader the nature of the interactions and their significance. It includes chapters on endophytes, arbuscular and ectomycorrhizal symbioses, leaf-interacting fungi, ‘sex, diseases and deception’ and soil fungal networks. It looks great (I could be biased as Jonathan and I wrote a chapter on molecular interactions in mycorrhizal development).

You can buy the book on Amazon.com.

EMBO Plant-Microbe Interactions

February 6th, 2012

Register now

30th New Phytologist Symposium

January 30th, 2012

 

The deadline for students and early-stage career scientists (researchers in their first post-doctoral position) applying for travel grants to the New Phytologist Trust is 18 May 2012 for the 30th New Phytologist Symposium. I would be grateful if you could forward this information to members of your research group who may be planning to apply for a grant.

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).

 

MPMI 2011 in Kyoto

February 20th, 2011

mpmiThe XV International Congress on Molecular Plant-Microbe Interactions will take place in Kyoto (Japan) from August 2 to 6, 2011.

The MPMPI meeting is recognized as one of the most important international meetings for those working on plant-microbe interactions. Through plenary lectures, concurrent sessions, special workshops and various events, attendees experience innovative plant-microbe interactions research.

Plenary Sessions (speakers and topics) are now Online.

Abstract submission is open.

Early Registration is also open.