Lichen symbiont interfaces revisited: ultrastructure of intraparietal contacts between fungal and algal cells in several microlichens with non-trebouxialean chlorobionts

作者：William B. Sanders, Asunción de los Rı́os · 发表于：The Lichenologist · 年份：2025 · DOI：10.1017/s0024282925101096 · 被引用次数：2 · 研究领域：Lichen and fungal ecology、Mycorrhizal Fungi and Plant Interactions、Botany and Plant Ecology Studies

Abstract This work attempts to better understand the significance of morphological diversity among fungal-algal contact zones present in lichens. We used TEM to examine a variety of lichen symbioses involving non-trebouxialean green algae that show intraparietal penetration by the mycobiont. A principal focus was on Endocarpon pusillum , a well-known member of a family ( Verrucariaceae ; Eurotiomycetes ) previously reported to be characterized by unwalled haustoria exposing a naked fungal protoplast. Peg-like haustoria arose from an inner layer(s) of the mycobiont cell wall that broke through outer layers and penetrated a short distance into the wall of the green algal symbiont ( Diplosphaera ). In both fungal and algal cells at the contact interface, lomasome-like vesicles and tubules occurred as modifications of the plasmalemma intermixed with wall materials at the inner surface of the cell wall. A fungal cell wall was consistently present around the haustorium, which resembled those depicted in earlier TEM studies of Verrucariaceae. Previously published micrographs of Verrucariaceae purporting to show wall-less haustoria surrounded by an empty space are believed to have been misinterpreted. However, in the isidiose Porina and foliicolous Calopadia , Byssoloma and Fellhanera species ( Lecanoromycetes ), we did observe extreme degrees of reduction in the mycobiont cell wall at symbiont contact interfaces. In those lichens, a broad area of the fungal cell bulged into the adja...