Cryoproective role of ribitol in Xanthoparmelia somloensis

Abstract

Thalli of Xanthoparmelia somloensis with natural content of polyols (control) and polyol-free thalli (acetone-rinsed) were used to study ribitol effects at low temperatures. Thalli segments were cultivated in ribitol concentration of 32 or 50 mM for 168 h at temperatures +5, 0, and -5 °C. The chlorophyll fluorescence parameters (potential yield of photochemical reactions in PS 2 (variable to maximum fluorescence ratio, F v /F m ), effective quantum yield of photochemical reactions in PS 2 (Φ PS2 ), and non-photochemical quenching (NPQ) were monitored in 24-h intervals using an imaging system. The effect of 32 mM ribitol on F v /F m and Φ PS2 was apparent only at -5 °C, however, the effect was seen throughout the whole exposure. Surprisingly, 50 mM ribitol concentration treatment led to a decrease in F v /F m and Φ PS2 and to an increase in NPQ values at -5 °C, while no change was observed at 0 °C and +5 °C. Acetone-rinsing caused decrease of F v /F m , Φ PS2 and NPQ.Additional key words: chlorophyll fluorescence imaging, fluorescence parameters, lichen thallus, low temperature, Trebouxia.

Enhanced culturing techniques for the mycobiont isolated from the lichen Xanthoria parietina

“…After confirming the optimal pH range for culturing the X. parietina mycobiont, we studied the individual effects of D-glucose and three sugar alcohols on growth. The sugar alcohols D-arabitol, D-mannitol and ribitol are known to occur in lichens and their isolated symbionts (Komiya and Shibata 1971;Honegger et al 1993;Alam et al 2015) and to play important roles for the lichen symbiosis (Hájek et al 2009a(Hájek et al , 2009bKosugi et al 2013). Ribitol and mannitol were also found in X. parietina symbionts, where these metabolites act as important energy source for metabolic processes (Eisenreich et al 2011).…”

“…Mannitol and ribitol also supported growth of lichenicolous fungi (Yoshino et al 2020). Furthermore, ribitol and mannitol are known cryoprotectants, enhancing the solubilization of fungal enzymes in lichen thalli during freezing events (Fontaniella et al 2000;Hájek et al 2009a). In addition, ribitol induced a concentration-dependent increase in the maximum quantum yield of photosystem II (F v /F m ) in lichen photobionts (Hájek et al 2009b).…”

Purification and characterization of a novel medium-chain ribitol dehydrogenase from a lichen-associated bacterium Sphingomonas sp.

“…External ribitol was reported to inhibit the transport of ribitol from the algae to the fungi in lichen thalli [5,37], leading to a decrease in the potential quantum yield of photosystem II [38]. From the viewpoint of lichen symbiosis, the sphingomonads can obtain benefits from that symbiosis as they utilize external ribitol not only for carbon sources but also to accelerate the transport of ribitol within the lichen [14].…”

“…From the viewpoint of lichen symbiosis, the sphingomonads can obtain benefits from that symbiosis as they utilize external ribitol not only for carbon sources but also to accelerate the transport of ribitol within the lichen [ 14 ]. On the other hand, while the photosynthetic process of lichen algae can be inhibited by low temperatures and osmotic stress [ 39 ], internal ribitol in the lichen can serve as a cryoprotectant and osmoprotectant by blocking the formation of ice crystals through steric mismatching of the hydrogen bonds formed between ribitol and water [ 11 , 38 ], thus stabilizing the structure of photosystem II and leading to increased photosynthesis in lichens [ 25 ]. The production of ribitol by algae can be stimulated in the symbiotic state [ 5 ]; thus, the green algae and mycobionts also benefit from the symbiosis with sphingomonads .…”

Adaptive biochemical mechanisms that ensure resistance of lichens to extreme environmental conditions (review)

“…Криопротекторная роль рибитола в Xanthoparmelia stenophylla (Ach.) Ahti & D. Hawksw была изучена группой ученых из Чехии [15].…”