Archive for September, 2012

A Putative Strigolactone Receptor

September 12th, 2012

Strigolactones are carotenoid-derived lactones involved in root development, arbuscular mycorrhizal symbiosis, branching and leaf senescence. These plant hormones are synthesized in the roots and transported acropetally to modulate axillary bud outgrowth (i.e., branching). In Current Biology Online NowCyril Hamiaux et al. have identified the DAD2 gene from petunia and present evidence for its roles in strigolactone perception and signaling. Their main findings are as follows:

  • DAD2 gene, identified by transposon tagging, encodes an α/β hydrolase fold protein,
  • DAD2 acts in the shoot; mutants are insensitive to strigolactones,
  • DAD2 crystal structure shows an internal cavity capable of binding strigolactones,
  • DAD2 can hydrolyze the strigolactone GR24.
  • These observations suggest that DAD2 acts to bind the mobile strigolactone signal and then interacts with PhMAX2A during catalysis to initiate an SCF-mediated signal transduction pathway.

    Figure: © Current Biology.

    Exploring the Mycorrhizal Genomes

    September 9th, 2012

     

    I hope you are wrapping up a good summer. I’m touching base to update you on our Mycorrhizal Genomics Initiative (MGI).

    The list of taxa of mycorrhizal fungi for the first series of analyses aiming to identify symbiotic traits has now been “frozen”. Thanks to Igor Grigoriev’s JGI team, this list includes an outstanding series of annotated genomes and transcriptomes from ectomycorrhizal, ericoid and orchid symbionts:

    • Amanita muscaria Koide
    • Hebeloma cylindrosporum h7  (v2.0),
    • Laccaria bicolor (v2.0),
    • Oidiodendron maius Zn,
    • Paxillus involutus,
    • Paxillus rubicundulus,
    • Piloderma croceum F 1598,
    • Pisolithus microcarpus 441,
    • Pisolithus tinctorius 270,
    • Scleroderma citrinum FougA,
    • Sebacina vermifera MAFF 305830,
    • Suillus luteus UH-Slu-Lm8-n1,
    • Tulasnella calospora AL13/4D,

    In addition, the following available transcriptomes will also be mined for symbiotic-related features:

    • Cenococcum geophilum
    • Cortinarius glaucopus,
    • Laccaria amethystina 08-1,
    • Lactarius quietus,
    • Meliniomyces bicolor,
    • Meliniomyces variabilis, and
    • Tricholoma matsutake 945.

    Finally, we will add the unpublished genomes of five saprotrophic agaricomycotina (including leaf-litter species) that we will use for identifying potential common genomic features in litter-borne and mycorrhizal fungi:

    • Jaapia argillacea MUCL-33604,
    • Hydnomerulium pinastri MD-312,
    • Plicaturopsis crispa FD-325 SS-3,
    • Hypholoma sublateritium FD-334 SS-4, and
    • Gymnopus luxurians FD-317 M1

    JGI has (or will soon) publicly released the web portals with the annotation for the above-mentioned fungal species. Visit the JGI Mycocosm database. In addition, we have released web sites for the corresponding transcriptome annotation at the Mycorhiza Genomics Initiative portal [restricted].

    To make good use of this tremendous genomic resource, we are organizing the 2nd MGI Workshop at the INRA-Nancy center in Champenoux (France), on November 13-14, 2012. The aim of the workshop is to bring together the consortium teams for discussing our findings. The format of the workshop will be roughly equally split between informal presentations summarizing the current findings and brainstorming about how to take advantage of the genome sequences to inform our understanding of symbiosis and fungal biology.

    On the following days, we will organize a New Phytologist Workshop entitled ‘ Bridging Mycorrhizal Genomics, Metagenomics & Forest Ecology‘. The workshop will also take place at INRA-Nancy over two days (Thursday 15 & Friday 16 November). The aim is to bring together a small group of MGI PI’s, fungal biologists and ecologists (20-25 attendees) to explore the future use of mycorrhizal genomes in order to both maximize the efficacy with which the community utilizes these technological breakthroughs in biology, ecology, phylogenetics, and forestry.

    Photo: Larch Bolete (Suillus grevellei) (Boletales), a close relative of the sequenced slippery Jack (Suillus luteus) (© F Martin).

    Myxomycetes

    September 8th, 2012

    “Slime mold or mould is a broad term describing protists that use spores to reproduce. Slime molds were formerly classified as fungi, but are no longer considered part of this kingdom. Their common name refers to part of some of these organisms’ life cycles where they can appear as gelatinous “slime”. This is mostly seen with the Myxomycetes, which are the only macroscopic slime molds.” in Wikipedia ‘Slime mold’.

    I’m looking around my iPhoto albums for recent images of woodlands and misty forest overstoreys to prep my 30 NPS talk and can’t seem to find anything but variations on fungi. So why resist? Last Spring, when exploring the stack of wood in my backyard after long rainy days, I tried to have  “glamor shots” of the new “Fungi” colonizers and I caught this spawn of uprising above-ground parts. These tiny fruiting body belong to one of the nine species of Myxomycetes found in Lorraine. They are sporangia of Cribaria rufa, C. vulgaris or C. ferruginea (JP Maurice, pers. com.).

    BTW, genomes of a few Myxomycetes have been released over the last years, including several genomes of the model genus Dictyostelium, see dictyBase

    Photo: Sporangia of Myxomycetes (© F Martin)