Secreted, glycosylated arginase from Xanthoria parietina thallus induces loss of cytoplasmic material from Xanthoria photobionts

A secreted, glycosylated arginase (lectin) from Xanthoria parietina thallus binds to the cell wall of Xanthoria photobiont when cell wall urease has p reviously been induced. The uptake of this secreted arginase by the algal c ell without cell wall ligand for the lectin increases the concentration of algal putrescine and it is followed by an apparent loss of chlorophyll. How ever, neither chlorophyllase activity has been detected nor chlorophyllide concentration increases after loading the cells with putrescine. The loss o f chlorophyll can be explained by the loss of algal protoplast resulting fr om the action of a putrescine-activated glucanase and the split of their me mbrane in an hypoosmotic medium. The loss and split of protoplasts have bee n shown by light and transmission electron microscopy.