MSA - Systematics/Evolution
McDonald, Tami , Armaleo, Daniele , Dietrich, Fred , Joneson, Suzanne , Lutzoni, Francois .
Is the acquisition of plant ammonium transporter genes by fungi key to the origin of the lichen symbiosis?
One fifth of all fungi live symbiotically with green algae, cyanobacteria or occasionally other photosynthesizers in obligate symbiotic relationships known as lichens. They are highly concentrated in a few closely related lineages of
the Pezizomycotina, suggesting that the lichen symbiosis could result from a few key innovations. Examination of the genome sequence of the lichen forming fungus Cladonia grayi revealed the presence of four ammonium transporter genes. Two of these belong to fungal ammonium transporter families MepB and MeaA. The remaining two have highest homology to plant-type ammonium transporters in the ammonium transporter 2 family (Amt2), which may be involved in ammonium re-uptake from the intercellular space. Homologues of these plant-type ammonium transporters were located by degenerate PCR and Southern blotting in other lichen-forming fungi in the subclasses Lecanoromycetidae, Chaetotheriomycetidae, and Dothidiomycetidae, but are absent from all published genomes of non-lichen-forming fungi with the exception of Penicillium marneffii. Phylogenetic analysis of all ammonium transporters in several fungal, plant and bacterial genomes showed the plant-type lichen-forming fungal ammonium transporters nested within the plant Amt2 clade, suggesting a horizontal gene transfer event early in the evolution of lichen-forming fungi, as well as a possible gene duplication event.
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1 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA
2 - Duke University, Molecular Genetics and Microbiology, Institute for Genome Sciences and Policy, 289 CARL Building, Research Drive, Durham, NC, 27710, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Cottonwood D/Snowbird Center
Date: Monday, July 27th, 2009
Time: 2:00 PM