By Diana Kenney
Staying alive in the desert is no simple matter for green algae whose evolutionary ancestors lived in the ocean. How can some algal species survive extreme drought, while others desiccate and die?
Two MBL scientists are finding out, in collaboration with the U.S. Department of Energy’s Joint Genome Institute (JGI). This month, Elena Lopez Peredo and Zoe Cardon received a highly competitive grant from JGI to sequence, annotate, and compare the genomes of four closely related species of green algae — two that dwell in desert and two from aquatic habitats.
“We hope to pinpoint genetic adaptations in the desert algae that allow them to withstand drought, such as protection of photosynthesis in arid versus wet environments,” says Cardon, a senior scientist in the Ecosystems Center. “Our comparisons also promise to reveal genetic blueprints for adaptations needed in these algae to make the evolutionary leap from water to desert habitats.”
“This research could also hint more broadly at how, throughout evolutionary history, aquatic organisms have emerged from water and sowed the once almost-barren Earth surface with life,” says Lopez Peredo, an MBL research associate.
One of the desert species to be studied, Scenedesmus deserticola, is especially drought resistant; it can dry up into a clump of dusty cells and, when rehydrated, fully revive and photosynthesize again. This species can even survive multiple cycles of desiccation and rehydration, while its closest aquatic relative, Scenedesmus obliquus, can’t withstand desiccation at all.
“What’s the difference between these two species? They are clearly closely related, but somewhere in their genomes, there is something coded completely differently,” says Lopez Peredo. The team will compare the genomes of these two species and two others from the Scenedesmus genus that have intermediate desiccation tolerance.
“This new funding endeavor exemplifies the extraordinary kinds of biological questions possible only at the MBL and highlights the incredible talent of our bright young scientists,” says Jonathan Gitlin, Director, MBL Division of Research. “We are so fortunate to have Elena working here and are most grateful to the DOE for their support of this innovative and important science.”
Photo captions: Desert microbiotic crust on mountainside outside Albuquerque, NM. Inset: The green algae Scenedesmus costatus and S. deserticola. Credit: Elena Lopez Peredo and Zoe Cardon