Lichen protein affinity towards walls of cultured and freshly isolated phycobionts and its relationship to cell wall cytochemistry

Abstract The binding capacity of protein fractions ( M _r > 8000) from five lichens, Hypocenomyce scalaris, Hypogymnia physodes, Ramalina fastigiata, Umbilicaria pustulata and Xanthoria parietina was tested towards their freshly isolated phycobionts and towards ten cultures of phycobionts, five of which were from the above-mentioned lichens. The protein fractions from H. scalaris, R. fastigiata, U. pustulata and X. parietina bind intensely to a cultured Pseudotrebouxia from H. physodes and a cultured Trebouxia from X. parietina , but not to the other cultured algae, and not to the freshly isolated algae. A protein fraction between M _r 3500 and 8000 from H. physodes shows a faint binding to its own cultured algae. The nature of the binding and its relevance in connection with the mutual recognition of alga and fungus are briefly discussed.