Fungal secondary compounds as sun-screens for symbiotic algae in lichens

Kjersti Bakkebø

A lichen is a successful symbiosis between an autotroph photobiont and a heterotroph mycobiont. The symbiotic association allows the organism to colonize a more diverse range of habitats, often with extreme environments.

In this symbiotic state, the photobionts are more tolerant to high irradiance than they otherwise would be, suggesting substantial photoprotection provided by the mycobiont. This protection is in the form of a pigmented cortical layer lying above the photobiont.

Most lichens produce some kind of cortical compound, for example, brown melanic pigments, orange anthraquinones or the yellow-green dibenzofurane usnic acid, each with the ability to absorb specific wavelengths in the solar spectrum.

Lichens present an interesting challenge in relation to the study of photoprotection in photosynthesizing organisms given their ability to flourish in extreme environments and their unique suitability for manipulation experiments.

Goals and objectives
The main goal of the project is to assess the sun-screening of lichen compounds, especially the UV screening, according to specific criteria for the demonstration of a screening function.

The seasonal changes in cortical compound production will also be examined in relation to the annual solar cycle and this will be related to photoprotection of the photobiont. Finally, lichen tolerance to the damaging elements of solar radiation, namely excessive heat and harmful UV wavelengths will be studied individually.

Project coordinators
Professor Yngvar Gauslaa, INA, UMB
Professor Knut Asbjørn Solhaug, INA, UMB

Project collaboration
Hana Vrablikova, Masaryk University, Brno, Czech Republic

Financed by
Norwegian University of Life Sciences (UMB)

Published: 01.04.05
Updated: 01.10.09
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Additional information

Publications

·Gauslaa, Y. & McEvoy, M. (2005) Seasonal changes in solar radiation drive acclimation of the sun-screening compound parietin in the lichen Xanthoria parietina. Basic and Applied Ecology 6: 75-82.