ABSTRACT
Lichenization is one of the most successful ways whereby fungi fulfill their requirement for carbohydrates, with about one-fifth of all known species of fungi being lichenized, i.e., forming an obligatory mutualistic association with a photoautotrophic green alga and/or a cyanobacterium. Although lichen-forming fungi account for a major part of fungal diversity, these obligatory symbiotic species are not randomly distributed within the fungal kingdom. This chapter explores the predispositions and consequences on fungal lineages that have survived various stresses associated with a transition to a lichenized state. To overcome extreme drought (some lichens can survive in a desiccated state for many years), lichens are equipped with extraordinary mechanisms protecting them from oxidative stress. The chapter focuses on the phenomenon of desiccation tolerance. It provides a review of mechanisms that protect desiccation-tolerant organisms from the deleterious effects of drought.
