Genome evolution of a nonparasitic secondary heterotroph, the diatom Nitzschia putrida

Ryoma Kamikawa, Takako Mochizuki, Mika Sakamoto, Yasuhiro Tanizawa, Takuro Nakayama, Ryo Onuma, Ugo Cenci, Daniel Moog, Samuel Speak, Krisztina Sarkozi, Andrew Toseland, Cock van Oosterhout, Kaori Oyama, Misako Kato, Keitaro Kume, Motoki Kayama, Tomonori Azuma, Ken-ichiro Ishii, Hideaki Miyashita, Bernard HenrissatVincent Lombard, Joe Win, Sophien Kamoun, Yuichiro Kashiyama, Shigeki Mayama, Shin-ya Miyagishima, Goro Tanifuji, Thomas Mock, Yasukazu Nakamura

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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 nonphotosynthetic osmotroph whose photosynthetic relatives contribute ca. 40% of net oceanic primary production. Comparative analyses with photosynthetic diatoms and heterotrophic algae with parasitic lifestyle revealed that a combination of gene loss, the accumulation 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 free-living secondary heterotroph.
Original languageEnglish
Article numbereabi5075
JournalScience Advances
Volume8
Issue number17
DOIs
Publication statusPublished - 29 Apr 2022

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