Decoding symbiosis: The two genomes of the lichen Cladonia grayi. July 23, 2012
Invited Lectures ; Daniele Armaleo, Olaf Mueller, Francois Lutzoni, Francis Martin, Emmanuelle Morin, Guillaume Blanc ; We analyzed the genomes of the lichen fungus Cladonia grayi (34 Mb) and its alga, Asterochloris sp. (56 Mb), sequenced using DNA from the isolated symbionts grown in culture. We used several approaches to distinguish genes relevant to the lichen symbiosis from those not specifically constrained by it. One method involved searching for genes with a phylogenetic signature characterized by an early burst of positive selection followed by stabilizing selection. Another was an analysis of gene family expansion and contraction in the symbionts compared to their phylogenetic relatives. Both fungus and alga contain expanded families of novel proteins as well as of known proteins. Finally, analyses of global transcriptional changes during early interactions between fungus and alga were combined with gene family data to further define genes relevant to symbiosis. Specific features will be discussed in detail.
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7th International Symbiosis Society Congress, Krakow, Poland