Parmales: an insight into the origin and evolutionary success of diatoms

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Parmales are an unknown small marine phytoplankton group with a silicified cell wall. Based on similarities in cell wall structure, Parmales has been proposed as a close relative of diatoms, the most successful microalgal group in modern oceans, and may play a key role in understanding their origin of silica cell wall and early evolution, which have not yet been clearly established. Recently, we isolated the first ever culture of Parmales in the Oyashio region of Japan. Molecular phylogenetic analysis of this culture indicated that Parmales was within the bolidophycean clade of autotrophic naked flagellates and a sister group of diatoms. We have studied on Parmales using ecological, physiological, genomic and biogeochemical approaches and analyzed their phylogenetic relationship between Bolidophycea and diatoms, chloroplast and mitochondria genomes, silica cell wall formation process, population dynamics in the Oyashio region, life cycle and specific biomarkers (molecular fossils).