Microheliella maris possesses the most gene-rich mitochondiral genome in Diaphoretikes

<p>The mitochondrial genomes are very diverse, but their evolutionary history is unclear due to the lack of efforts to sequence that of protists (unicellular eukaryotes), which cover a major part of the eukaryotic tree. Cryptista comprises cryptophytes, goniomonads, kathablepharids, and <em>Palpitomonas bilix</em>, and their mitochondrial genomes (mt-genomes) are characterized by various gene contents, particularly the presence/absence of an ancestral (bacterial) system for the cytochrome c maturation system. To shed light on mt-genome evolution in Cryptista, we report the complete mt-genome of <em>Microheliella maris</em>, which was recently revealed to branch at the root of Cryptista. The <em>M. maris</em> mt-genome was reconstructed as a circular mapping chromosome of 61.2 kbp with a pair of inverted repeats (12.9 kbp) and appeared to be the most gene-rich among the mt-genomes of the members of Diaphoretickes (a mega-scale eukaryotic assembly including Archaeplastida, Cryptista, Haptista, and SAR) studied so far, carrying 53 protein-coding genes. With this newly sequenced mt-genome, we inferred and discussed the evolution of the mtgenome in Cryptista and Diaphoretickes.</p>