Interface between fungi and green algae in lichen associations

Abstract

It is widely recognized that the lichen is the product of a fungus and a photosynthetic partner (green alga or cyanobacterium) but its acceptance was slow to develop throughout history. The development of powerful microscopic and other lab techniques enabled better understanding of the interface between symbionts beginning with the contentious concept of the dual nature of the lichen thallus. Even with accelerating progress in understanding the interface between symbionts, much more work is needed to reach a level of knowledge consistent with that of other fungal interactions. This review describes the interface between algal and fungal symbionts in lichens, including the appearance of interacting symbionts, our current understanding of communication between symbionts, and emerging new concepts in light of the challenges and debates that have provided lichenology with an enriched history. Communication between symbionts occurs before physical contact, which has been studied by microscopy, movement of molecules between symbionts, and gene expression studies. New discoveries include the interaction with more than one alga in a lichen thallus as well as other unrelated fungi and bacteria typically found on or within the thallus. This mini review briefly describes our current state of knowledge and highlights new directions for further study.

Two Basidiomycete Fungi in the Cortex of Wolf Lichens

“…Instead, we observed wall-to-wall contact with algal cells, which has not previously been reported for lichen-associated Tremella. The contacts are strikingly similar to hyphal-algal enmeshing that is often taken as the basis for recognizing successful lichen resynthesis in vitro [29][30][31]. The contacts formed by Tremella resemble intraparietal haustoria formed by the dominant ascomycete on algal cell walls [32], but ultrastructural studies are needed to verify the extent and type of penetration into the algal cell.…”

Harnessing fungal bio-electricity: a promising path to a cleaner environment

“…The synergy between fungi and microalgae promotes one another’s growth. Nutrient sharing and gas exchange enhance the individual’s metabolic activity, and fungi can provide shelter to microalgae (like lichens) ( Piercey-Normore and Athukorala, 2017 ). Therefore, the consortium can accumulate nutrients from the surroundings.…”

Sustained beneficial infections: priority effects, competition, and specialization drive patterns of association in intracellular mutualisms

“…Representing more than 20% of all fungal species, this polyphletic host and symbiont partnership is a common nutritional strategy involving translocation of photosynthates whereby extracellular photobiont cells are integrated with fungal partners via complex haustorial or appressorial structures (Honegger, 1998). These associations range from low to high degrees of partner specificity with examples of coinfection with multiple phycobiont lineages within single thalli (e.g., Blaha et al, 2006;Mansournia et al, 2012;Molins et al, 2013;Kosecka et al, 2020;Piercey-Normore and Athukorala, 2017;Yahr et al, 2004). "Algal switching" has also been observed (Ohmura et al, 2019).…”