Secreted, Glycosylated Arginase from Xanthoria parietina Thallus induces Loss of Cytoplasmic Material from Xanthoria Photobionts

Abstract

A secreted, glycosylated arginase (lectin) from Xanthoria parietina thallus binds to the cell wall of Xanthoria photobiont when cell wall urease has previously been induced. The uptake of this secreted arginase by the algal cell without cell wall ligand for the lectin increases the concentration of algal putrescine and it is followed by an apparent loss of chlorophyll. However, neither chlorophyllase activity has been detected nor chlorophyllide concentration increases after loading the cells with putrescine. The loss of chlorophyll can be explained by the loss of algal protoplast resulting from the action of a putrescineactivated glucanase and the split of their membrane in an hypoosmotic medium. The loss and split of protoplasts have been shown by light and transmission electron microscopy.

Key Words:

• Xanthoria parietina
• chlorophyll
• glucanase
• lectin
• protoplast
• putrescine
• secreted arginase