Phylogeny and evolution of haptophytes based on three new mitogenomes

Abstract

Emiliania, Chrysochromulina, and Phaeocystis are important primary producers in the open ocean. Diacronema (known as Pavlova) and Isochrysis are famous microalgae with higher amounts of polyunsaturated fatty acids and are commonly used as feedstocks of marine shellfish and fish aquacultures. Despite of industrial, ecological and evolutionary importance of the haptophytes, genetic diversity and evolutionary history of the lineage are not well studied yet because of limited taxon sampling. In present study, we assembled new mitochondrial genomes (mtDNA) from three haptophycean taxa, i.e., Chrysotila carterae LIMS-PS-1065, Diacronema lutheri LIMS-PS-0073, and Isochrysis galbana LIMS-PS-1699. In the Haptophytes, total size of mtDNA was ranged from 26,188 bp to 41,838 bp in total, and encompassed 17-22 protein coding genes, 2-3 rRNAs, and 24-25 tRNAs. The best phylogeny based on mtDNA reveals a monophyly of Haptophyta, basal position of Pavlovales (Diacronema and Pavlova), and relationships among Coccolithophycean taxa, such as sister relationship of Coccolithales (Chrysotila) and Isochrysidales (Eminiania and Isochrysis). The gene content comparison based on mtDNA phylogeny suggested multiple gains and losses of atp4, atp8, rpl14, rps3 and rps8 within the haptophytes.