Message - 7th IAL Symposium

The 7 th International Association for Lichenology Symposium 2012
3I: New approaches to understanding biosynthesis and ecological roles of
metabolites in lichens
(3I - O1) Submission ID: IAL0144-00001
GAINING NEW INSIGHTS INTO LICHEN SECONDARY METABOLISM: ECOLOGICAL FAC-
TORS TRIGGER CHEMOSYNDROMIC VARIATION WITHIN SPECIES OF THE GENUS
XANTHOPARMELIA AND NOVEL TECHNIQUES TO DECIPHER THE GENETIC POTENTIAL
OF POLYKETIDE BIOSYNTHESIS IN A CULTURED METABOLITE-PRODUCING MYCOBIONT
Stocker-Wörgötter E. 1
1 University of Salzburg, Organismic Biology, Salzburg, Austria
The ecological role and functions of secondary metabolites, particularly medullary compounds, has
been extensively discussed among lichenologists since a long time. Variations in medullary chemistry within
many lichen families and genera have generated debate over the recognition of “chemical species”. A series
of patterns of chemical variations have been identified as replacement-type substances, accessory-type
compounds, acid deficient, acid additive strains and also the occasional presence of chemosyndromes, even
overlapping chemosyndromes have been reported. In many lichen groups, which have been screened for the
content of lichen substances by TLC and HPLC analyses, major compounds in a particular taxon are often accompanied
by minor, biosynthetically related satellite compounds, which in turn may become predominant in
closely related taxa – this is known as chemosyndromic variation. Variations in chemical composition of secondary
metabolites in lichens have been used as important taxonomic characters at different levels in lichen
systematic. The precise taxonomic significance of such variation has been often discussed but may be best
understood a posteriori and in conjunction with other characters. Chemical analyses indicate that substantial
chemical variation is possible both within a species and among closely related species. Chemosyndromic variation
has been correlated with morphology (differences in chemistry co-occurring with morphological, anatomical
differences), geographic variation (reproductive isolation) and also with ecology. Our recent investigations with
Australian and European species of the genus Xanthoparmelia have mainly focused on ecological factors that
may be responsible for chemosyndromic variation within Australian species like Xanthoparmelia antleriformis,
X. cheelii, X. filarszkyana, X. flavescentireagens, X. lineola, X. metaclystoides, X. substrigosa, X. tasmanica, X.
flavecentireagens, and X. conspersa from Europe. Distinct medullary chemistries, growth forms, and the production
of vegetative diaspores have been found to have evolved independently multiple times in Xanthoparmelia.
Chemical variation was also studied in cultured mycobionts. One mycobiont (X. flavecentireagens) cultured in
large scale/desiccation stress that yielded a complete chemosyndrome was selected to decipher the PKS genes
coding for the respective PKSs, e.g. for norlobaridone, loxodin (medullary depsidones) and usnic acid (cortical
dibenzofuran).
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3I-O