Message - 7th IAL Symposium

The 7 th International Association for Lichenology Symposium 2012
1B: Genomic approaches to studying the lichen symbiosis
(1B-O1) Submission ID: IAL0319-00001
APPROACHING LICHENS BY UNWINDING COMPLEMENTARY GENOMES:
AN INTRODUCTION
Miao V. 1 , Armaleo D. 2
1 Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
2 Department of Biology, Duke University, Durham, United States
Lichen symbionts are unique in their near-absolute dependence on each other in nature, accompanied
by occasional streaks of independence most obvious in aposymbiotic culture. This session will look at this
balancing act from a genomics perspective. Superficially, the symbionts’ genomes are not very different from
those of their non-symbiotic fungal and algal relatives. They have not degenerated so as to produce absolute
dependence between mycobiont and photobiont, but have evolved in subtle ways to cement an intimate and
successful interaction while maintaining each partner’s individuality. We will look not only at the general structure
of several lichen genomes, but also at features connected with their functioning in the symbiosis: changes in
gene families, presence of genes unique to lichens, transcriptional adaptations, metabolic adaptations, epigenetic
changes. We will survey the mycobiont of Xanthoria parietina, two closely related Peltigera species and
their cyanobionts, Cladonia grayi and its Asterochloris sp. photobiont, horizontal gene transfer in Trebouxia, and
the effect of different ecological conditions on the larger bacterial communities inhabiting various lichens.
(1B-O2) Submission ID: IAL0293-00001
GENOME SEQUENCING OF XANTHORIA PARIETINA 46-1-SA22
Dyer P. S. 1 , Crittenden P. D. 1 , Archer D. B. 1 , Barry K. 2 , Foster B. 2 , Copeland A. 2 , Kuo A. 2 , Grigoriev I. 2
1 School of Biology, University of Nottingham, Nottingham, United Kingdom
2 Eukaryotic Genome Program, DOE Joint Genome Institute, Walnut Creek, United States
Xanthoria parietina has been chosen as a representative lichen-forming fungus for genome sequencing.
This species was nominated because it has a wide distribution (being found in temperate and circumpolar
regions worldwide), has a characteristic stratified thallus morphology, is amenable to axenic cultivation, and is
one of the most commonly studied lichenized fungi. It can occur on a variety of substrata including rock, tree
bark and man-made surfaces. To enable genome studies, ascospore progeny from an individual thallus of X.
parietina were collected from the Peak District, UK, and grown in axenic culture to allow extraction of DNA purely
of the fungal mycobiont. Sequencing of the genomic DNA by 454 and Illumina pyrosequencing technology has
now been completed at the DOE Joint Genome Institute. Preliminary analysis reveals a 32 Mbp size genome
(typical of pezizomycete fungi) with an estimated 10,800 genes of average size 1,505 nt encoding an average
protein length of 432 amino acids. In further work, mRNA samples are being extracted from both the symbiotic
(field thallus) and non-symbiotic (axenic pure culture) states of X. parietina prior to library construction and whole
transcriptome sequencing (“RNA seq”). Arising data will be used for training of the genome auto-annotation process,
and it is anticipated that comparison of transcriptome pools will yield insights into differential regulation of
genes in the symbiotic versus non-symbiotic state. A multinational genome annotation group has been set up to
assist with the genome annotation and analysis.
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1B-O