Porphyra: Complex Life Histories in a Harsh Environment: P. umbilicalis, an Intertidal Red Alga for Genomic Analysis

Porphyra encompasses a large group of multicellular red algae that have a prominent gametophytic phase. The complex, heteromorphic life history of species in this genus, their remarkable resilience to high light and desiccation, ancient fossil records, and value as human food (e.g., laver, nori), make Porphyra a compelling model for genome sequencing. Sequencing of the nuclear genome of Porphyra umbilicalis from the northwestern Atlantic is currently in process. The ∼270 Mb genome of this alga is much larger than that of the unicellular acidophilic Cyanidioschyzon merolae (16.5 Mb), the only rhodophyte for which there is a fully sequenced genome, and is approximately twice as large as the Arabidopsis genome. Future analyses of the P. umbilicalis genome should provide opportunities for researchers to (1) develop an increased understanding of the ways in which these algae have adapted to severe physiological stresses, (2) elucidate the molecular features of development through the complex life history, and (3) define key components required for the transition of growth from a single cell to a multicellular organism.