Desert green algae show higher desiccation tolerance than their aquatic
sister-species
Abstract
Diverse algae possess vegetative desiccation tolerance, the ability to
recover from extreme desiccation without forming specialized resting
structures. Green algal genera such as Tetradesmus (Sphaeropleales,
Chlorophyceae) contain both terrestrial and aquatic species, providing
an opportunity to compare physiological traits associated with the
transition to land in closely related taxa. We subjected six species
from aquatic and terrestrial habitats to three desiccation treatments
varying in final relative humidity followed by short- and mid-term
rehydration. We tested the capacity of the algae to recover from
desiccation using the effective quantum yield of photosystem II as a
proxy for physiological activity. The degree of recovery was dependent
both on the habitat of origin and the desiccation scenario, with
terrestrial, but not aquatic species, recovering from desiccation.
Distinct strains of each species responded similarly to desiccation and
rehydration, with the exception of one aquatic strain that recovered
from the mildest desiccation. Cell ultrastructure was uniformly
maintained in both aquatic and desert species during dehydration and
rehydration, but staining with an amphiphilic styryl dye indicated
desiccation-induced damage to the plasma membrane in the aquatic
species. These analyses demonstrate that terrestrial Tetradesmus possess
the vegetative desiccation tolerance phenotype, making these species
ideal for comparative omics studies.