Contrasting strategies used by lichen microalgae to cope with desiccation–rehydration stress revealed by metabolite profiling and cell wall analysis

Abstract

Most lichens in general, and their phycobionts in particular, are desiccation tolerant, but their mechanisms of desiccation tolerance (DT) remain obscure. The physiological responses and cell wall features of two putatively contrasting lichen-forming microalgae, Trebouxia sp. TR9 (TR9), isolated from Ramalina farinacea (adapted to frequent desiccation-rehydration cycles), and Coccomyxa solorina-saccatae (Csol), obtained from Solorina saccata (growing in usually humid limestone crevices, subjected to seasonal dry periods) was characterized. Microalgal cultures were desiccated under 25%-30% RH and then rehydrated. Under these conditions, RWC and ψw decreased faster and simultaneously during dehydration in Csol, whereas TR9 maintained its ψw until 70% RWC. The metabolic profile indicated that polyols played a key role in DT of both microalgae. However, TR9 constitutively accumulated higher amounts of polyols, whereas Csol induced the polyol synthesis under desiccation-rehydration. Csol also accumulated ascorbic acid, while TR9 synthesized protective raffinose-family oligosaccharides (RFOs) and increased its content of phenolics. Additionally, TR9 exhibited thicker and qualitatively different cell wall and extracellular polymeric layer compared with Csol, indicating higher water retention capability. The findings were consistent with the notion that lichen microalgae would have evolved distinct strategies to cope with desiccation-rehydration stress in correspondence with the water regime of their respective habitats.

The complexity of symbiotic interactions influences the ecological amplitude of the host: A case study inStereocaulon(lichenized Ascomycota)

“…In case of two other phycobiont genera, these problems have not occurred because of more acceptable species‐level lineages of mycobionts, including several common ones. Tolerance of Vulcanochloris towards extreme drought should be confirmed by culture experiments and compared with that of Asterochloris (e.g., Gasulla et al., ) or other trebouxiophycean phycobionts (Candotto‐Carniel et al., ; Centeno, Hell, Braga, del Campo, & Casano, ).…”

“…of Vulcanochloris towards extreme drought should be confirmed by culture experiments and compared with that of Asterochloris (e.g., Gasulla et al, 2013) or other trebouxiophycean phycobionts (Candotto-Carniel et al, 2016;Centeno, Hell, Braga, del Campo, & Casano, 2016).…”

Symbiosis between river and dry lands: phycobiont dynamics on river gravel bars

“…A comparable phycobiont pair Trebouxia jamesii / Trebouxia sp. TR9 found in Ramalina farinacea lichen is assumed to bring physiological benefits to that symbiotic system (Casano et al 2011; Centeno et al 2016). Alternatively, the minority phycobionts could occur in thalli without direct effects to the lichen.…”

Overexpression of BdMATE Gene Improves Aluminum Tolerance in Setaria viridis

“…To the dried samples were added 100 μL of pyridine and 50 μL of BSTFA (N,O-bis(trimethylsilyl)trifluoroacetamide) + 1% TMCS (trimethylchlorosilane). The analysis of GC/MS was performed according to Centeno et al (2016) on a 30 m HP5 column with 0.25 mm of diameter and 0.25 μM film thickness (Supelco). Helium was used as the carrier gas at a flow rate of 1 mL min -1 .…”