Thriving in a tough environment

Spare a thought for seaweeds such as the red alga Porphyra umbilicalis (laver or Atlantic nori), which survives in the intertidal zone, experiencing 4 different environments each day due to day:night and high and low tides. Sequencing of its genome has revealed several insights into how it manages to achieve this, including cell wall features, many ultraviolet/high light and thermal protection strategies, and a wealth of nutrient transporters.

An international research team of 50 scientists, led by Susan Brawley at the University of Maine, Orono, USA, was responsible for the work, published in the Proceedings of the National Academy of Sciences (http://www.pnas.org/content/early/2017/07/14/1703088114), with financial support for the sequencing from the Joint Genome Institute of the U.S. Department of Energy, and grants from the U.S. National Science Foundation (NSF) to support analyses.

The analysis of the Porphyra genome and the team's comparative analysis to available nuclear genomes of other red algae revealed novel features, including unique signaling molecules and augmented stress tolerance mechanisms. Moreover, the reduced number of genes for motor proteins and cytoskeletal elements offers a potential explanation for why the red algae are constrained to small stature relative to other multicellular lineages.

Katherine Helliwell and Ulrich Johan Kudahl from Alison Smith’s group worked on the genes for vitamin metabolism in P. umbilicalis. Laver has long been considered to be a good source of vitamin B12, but only bacteria can synthesize this important organic micronutrient. Porphyra is characterised by its own microbiome, and was found to have genes encoding proteins that can remodel a non-bioaccessible form of the vitamin, pseudocobalamin, to cobalamin, making it bioaccessible both to Porphyra and to humans who eat laver.

Susan H Brawley et al. (2017) Insights into the red algae and eukaryotic evolution from the genome of Porphyra umbilicalis (Bangiophyceae, Rhodophyta) PNAS