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Climate change - can lichens protect themselves using UV-induced melanins? Richard Peter Beckett and Knut Asbjørn Solhaug Cape Town May 2014 Lichen Melanins Norwegian University of Life Sciences 1 What are lichens? Lichens – symbiosis between a fungus (95%) and an alga (5%) Introduction to Lichens Alga (green or cyanobacterium) Fungus (ascomycete) Evolution • Probably evolved around 400 – 600 million years ago (i.e. lichens “greened the earth”). • They are special! Section of lichen fossil Section of living lichen Whole is greater than the sum of the parts! Lichens are differentially sensitive to sulphur dioxide! Allows rapid knowledge of sulphur dioxide levels… Bare bark Above 200 ppm Algae About 170 ppm Lecanora Xanthoria About 50 ppm Ramalina Lobaria Less than 30 ppm About 35 ppm About 150 ppm Important components of soil crusts, are very widespread in southern Africa. Much work needs to be done! Stabilize soil! Typical lichen secondary metabolites “Peltigeralean” lichens are low in secondary metabolites, others rich Cell Wall Redox Enzymes • In early work we showed presence of laccases, tyrosinases and peroxidases in Peltigeralean lichens • These enzymes are almost absent in other species Preliminary sequence data suggest classic tyrosinases Liers et al. (2014) in prep Role of Tyrosinases Probably linked to melanization….. • UV induces melanin synthesis in lichens (photoprotection) • In non-Peltigeralean species melanins may be synthesized by polyketide synthases?? Examples of lichens with melanins UV-B induced melanins Cetraria islandica with most melanin in its upper parts Lobaria pulmonaria Lichen Melanins Norwegian University of Life Sciences 16 Interaction of climate change and melanins on lichens Lichen melanins Norwegian University of Life Sciences 17 Background for collaboration • Lichen ecology and physiology have been studied in both South Africa and Norway. • We have met at several conferences and have for a quite long time looked for funding for joint projects. • The expertise on lichen ecology and physiology in Norway and South Africa is quite different. • By combining the best expertise and methods available, important increase in the knowledge on how climate change affect lichen ecosystems is expected. Lichen melanins Norwegian University of Life Sciences 18 Importance of lichens • Ecologically, lichens play key roles in both South Africa and Norway. • For southern African soil crusts, loss of lichens likely results in severe erosion and significant losses of nitrogen fixation capacity. Lichen melanins Norwegian University of Life Sciences 19 Hypotheses to be tested • Melanin synthesising enzymes in South African and Norwegian lichens • Effects of UV on melanin synthesising enzymes. • Does melanin increase the susceptibility to heat damage? • Is there a trade-off between radiation screening and photosynthetic light use efficiency in melanic lichens? • Identification of nitrogen-containing eumelanins and nonnitrogen allomelanins in South African and Norwegian lichens. Lichen melanins Norwegian University of Life Sciences 20
