Antigenic similarities and differences between symbiotic and cultured phycobionts from the lichen, Xanthoria parietina

Lichen phycobionts are known to undergo a series of morphological, physiological, and biochemical changes as a result of lichenization [1-3]. A number of modifications in the cell wall of lichen algae have also been described [4]. Using ' the phycobiont of Xanthoria parietina as a study organism, we have shown that concanavalin A bound to the cell wall of lichen algae cultured in vitro, but not to the same algae in the symbiotic form (freshly isolated from the lichen) [5]. We have also isolated a crude protein fraction from the lichen, a component(s) of which bound to the cell wall of cultured, but not freshly isolated algae. Binding was correlated to cytochemical features present only on the cell wall of cultured algae [6]. With the aid of a solid phase radioimmunoassay, we now show that there are also detectable antigenic differences, as well as similarities, between freshly isolated and cultured phycobionts from X. parietina.