Photosynthetic recovery following desiccation of desert green algae (Chlorophyta) and their aquatic relatives

Abstract

Recent molecular data suggest that desert green algae have evolved from freshwater ancestors at least 14 times in three major classes (Chlorophyceae, Trebouxiophyceae and Charophyceae), offering a unique opportunity to study the adaptation of photosynthetic organisms to life on land in a comparative phylogenetic framework. We examined the photorecovery of phylogenetically matched desert and aquatic algae after desiccation in darkness and under illumination. Desert algae survived desiccation for at least 4 weeks when dried in darkness, and recovered high levels of photosynthetic quantum yield within 1 h of rehydration in darkness. However, when 4 weeks of desiccation was accompanied by illumination, three of six desert taxa lost their ability to recover quantum yield during rehydration in the dark. Aquatic algae, in contrast, recovered very little during dark rehydration following even just 24 h of desiccation. Re-illuminating rehydrated algae produced a nearly complete recovery of quantum yield in all desert and two of five aquatic taxa. These contrasts provide physiological evidence that desert green algae possess mechanisms for photosynthetic recovery after desiccation distinct from those in aquatic relatives, corroborating molecular evidence that they are not happenstance, short-term visitors from aquatic environments. Photosensitivity during desiccation among desert algae further suggests that they may reside in protected microsites within crusts, and species specificity of photosensitivity suggests that disturbances physically disrupting crusts could lead to shifts or losses of taxonomic diversity within these habitats.

Ecophysiological performance of an urban strain of the aeroterrestrial green algaKlebsormidiumsp. (Klebsormidiales, Klebsormidiophyceae)

“…However, in contrast to Klebsormidium sp., recovery of photosynthesis in dried algal cells occurred within minutes after artificial moistening (Ha¨ubner et al, 2006). Similar high tolerance against desiccation has been described for other aeroterrestrial green algae such as Apatococcus lobatus (Bertsch, 1966), Klesormidium flaccidum (De Winder et al, 1990) and various desert green algae (Gray et al, 2007). Klebsormidium flaccidum can survive in dehydrated conditions and can maintain 80-90% of photosynthetic CO 2 fixation for some time after almost complete loss of cellular water (De Winder et al, 1990).…”

“…Klebsormidium flaccidum can survive in dehydrated conditions and can maintain 80-90% of photosynthetic CO 2 fixation for some time after almost complete loss of cellular water (De Winder et al, 1990). Desert green algae even survived desiccation for at least 4 weeks when dried in darkness and already exhibited high photosynthetic recovery rates only 1 h after rehydration while their aquatic pendants recovered very little (Gray et al, 2007). Compared with the high desiccation tolerance and recovery potential of these aeroterrestrial green algae, the studied Klebsormidium sp.…”

“…More recent data suggest that shading effects due to such three-dimensional spatial arrangements may be more important than appreciated in the past. Gray et al (2007) reported a very interesting case in terrestrial green algae occurring in biotic crusts of North American deserts. Despite their ability to withstand desiccation, these algae were susceptible to photodamage at a PFD of 130 mmol m À2 s…”

“…Gray et al (2007) suggested that in the field these algae may occupy microenvironments within the crust where they are protected from damaging light levels; the differential susceptibility to irradiance expressed by individual taxa suggests that there may be a complex spatial arrangement of green algal species in the crust, structured in response to the attenuation of light with depth through the crust proEle. Although self-shading is poorly understood in aeroterrestrial green algal assemblages, it has been well investigated in Ulva macroalgal canopies in southern Spain, where C) followed by 48 h recovery after rehydration with stock culture medium.…”

Phylogeography of microbial phototrophs in the dry valleys of the high Himalayas and Antarctica

“…Chlamydopodium vacuolatum (M63001) and Pleurastrum insigne (Z28972) are terrestrial algae [31,34], whereas Chlamydopodium sp. (EF159950) was isolated from a north temperate lake [45]. geographical distance for all sequences from this clade.…”