Multiple losses of photosynthesis in Nitzschia (Bacillariophyceae)

TitleMultiple losses of photosynthesis in Nitzschia (Bacillariophyceae)
Publication TypeJournal Article
Year of Publication2015
AuthorsKamikawa R, Yubuki N, Yoshida M, Taira M, Nakamura N, Ishida K-ichiro, Leander BS, Miyashita H, Hashimoto T, Mayama S, Inagaki Y
JournalPhycological Research
Volume63
Pagination19–28
ISSN13220829
Keywordsapochlorotic diatoms, genetic diversity, large subunit rrna, molecular phylogenetic analysis, nonphotosynthetic plastids, plastid 16s rrna, rcc
Abstract

In order to obtain insights into the evolution of colorless (apochlorotic) diatoms, we investigated newly established apochlorotic strains of Nitzschia spp. using light and electron microscopy and molecular phylogenetic analyses. Fluores- cence microscopic observations demonstrated that the apochlorotic diatoms lack chlorophylls. Transmission electron microscopy of two apochlorotic strains also demonstrated that their plastids lacked thylakoids; instead, having four- membrane-bound organelles without thylakoids, similar to nonphotosynthetic plastid remnants. From the apochlorotic strains, we also found plastid small subunit rRNA genes that were unusually long branched in phylogenetic analyses, as observed in other nonphotosynthetic plastids. Molecular phylogenetic analysis of the nucleus-encoded large subunit rRNA genes showed eight distinct lineages for apochlo- rotic diatoms. The eight apochlorotic lineages were not monophyletic, suggesting that the loss of photosynthesis took place multiple times independently within Nitzschia. Several diatoms, including Nitzschia spp., are mixotrophic, which is an expected mode of nutrition that would help explain the evolutionary switch from a photosynthetic lifestyle to a heterotrophic lifestyle. Key

URLhttp://doi.wiley.com/10.1111/pre.12072
DOI10.1111/pre.12072