@article {Kamikawa2021.01.24.427197, author = {Ryoma Kamikawa and Takako Mochizuki and Mika Sakamoto and Yasuhiro Tanizawa and Takuro Nakayama and Ryo Onuma and Ugo Cenci and Daniel Moog and Samuel Speak and Krisztina Sarkozi and Andrew Toseland and Cock van Oosterhout and Kaori Oyama and Misako Kato and Keitaro Kume and Motoki Kayama and Tomonori Azuma and Ken-ichiro Ishii and Hideaki Miyashita and Bernard Henrissat and Vincent Lombard and Joe Win and Sophien Kamoun and Yuichiro Kashiyama and Shigeki Mayama and Shin-ya Miyagishima and Goro Tanifuji and Thomas Mock and Yasukazu Nakamura}, title = {Genome evolution of a non-parasitic secondary heterotroph, the diatom Nitzschia putrida}, elocation-id = {2021.01.24.427197}, year = {2021}, doi = {10.1101/2021.01.24.427197}, publisher = {Cold Spring Harbor Laboratory}, abstract = {Secondary loss of photosynthesis is observed across almost all plastid-bearing branches of the eukaryotic tree of life. However, genome-based insights into the transition from a phototroph into a secondary heterotroph have so far only been revealed for parasitic species. Free-living organisms can yield unique insights into the evolutionary consequence of the loss of photosynthesis, as the parasitic lifestyle requires specific adaptations to host environments. Here we report on the diploid genome of the free-living diatom Nitzschia putrida (35 Mbp), a non-photosynthetic osmotroph whose photosynthetic relatives contribute ca. 40\% of net oceanic primary production. Comparative analyses with photosynthetic diatoms revealed that a combination of genes loss, the horizontal acquisition of genes involved in organic carbon degradation, a unique secretome and the rapid divergence of conserved gene families involved in cell wall and extracellular metabolism appear to have facilitated the lifestyle of a non-parasitic, free-living secondary heterotroph.Competing Interest StatementThe authors have declared no competing interest.}, URL = {https://www.biorxiv.org/content/early/2021/01/24/2021.01.24.427197}, eprint = {https://www.biorxiv.org/content/early/2021/01/24/2021.01.24.427197.full.pdf}, journal = {bioRxiv} }