A model suite of green algae within the Scenedesmaceae for investigating contrasting desiccation tolerance and morphology

Abstract

Microscopic green algae inhabiting desert microbiotic crusts are remarkably diverse phylogenetically, and many desert lineages have independently evolved from aquatic ancestors. Here we worked with five desert and aquatic species within the family Scenedesmaceae to examine mechanisms that underlie desiccation tolerance and release of unicellular versus multicellular progeny. Live cell staining and time-lapse confocal imaging coupled with transmission electron microscopy established that the desert and aquatic species all divide by multiple (rather than binary) fission, although progeny were unicellular in three species and multicellular (joined in a sheet-like coenobium) in two. During division, Golgi complexes were localized near nuclei, and all species exhibited dynamic rotation of the daughter cell mass within the mother cell wall at cytokinesis. Differential desiccation tolerance across the five species, assessed from photosynthetic efficiency during desiccation/rehydration cycles, was accompanied by differential accumulation of intracellular reactive oxygen species (ROS) detected using a dye sensitive to intracellular ROS. Further comparative investigation will aim to understand the genetic, ultrastructural and physiological characteristics supporting unicellular versus multicellular coenobial morphology, and the ability of representatives in the Scenedesmaceae to colonize ecologically diverse, even extreme, habitats.

A new approach towards the so-called recalcitrant seeds

“…Some advances have been obtained, for instance, with fungus control (Figure 2A) during storage, one of the main problems since seeds are stored moist and often at temperatures that do not totally inhibit the development of microorganisms (Oliveira et al, 2011;Parisi et al, 2013;Françoso and Barbedo, 2014;Hennipman et al, 2017). Studies on desiccation tolerance, although essential, are not exclusive to seeds, but include ferns (Fallard et al, 2018), mosses (Xiao et al, 2018), fungi (Jackson et al, 2006), algae (Cardon et al, 2018), and even animals such as insects (Kellermann et al, 2018) and amphibians (Eads et al, 2012), evidently each within certain limits of interest in the specific areas. However, even extreme limits of desiccation tolerance are not exclusive to seeds, being studied, for instance, in microorganisms (Mascarin et al, 2018), ressurection plants (Sun et al, 2018), rotifers (Nowell et al, 2018), and larvae of insects (Sogame and Kikawada, 2017) and crustaceans (Janis et al, 2017).…”

Extraction of high‐quality, high‐molecular‐weight DNA depends heavily on cell homogenization methods in green microalgae

“…The residual light was integrated to generate an optical image. The nuclei were visualized using the ds DNA stain SYBR safe (yellow, 450/50 band pass filter) and the chloroplasts’ chlorophyll fluorescence (red, 595/50 band pass filter) (see Cardon et al., for details). Scale bars = 5 μm.…”

“…A), which accumulate during cellular division. These algal species within the Scenedesmaceae divide asexually through multiple fission (Cardon et al., ). During this process, a mother cell undergoes multiple rounds of nuclear division followed by cellular division.…”

Desert green algae show higher desiccation tolerance than their aquatic sister-species

“…For example, desiccation in the dark resulted in the recovery of more species (Gray et al 2007). In Scenedesmaceae (a family including Tetradesmus ), algae isolated from desert soil crusts recover photosynthetic activity three minutes after rehydration and to a much higher degree than the aquatic species (Cardon et al 2018). They also demonstrated variation in recovery among the desert algae.…”