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Multiple losses of photosynthesis in N itzschia ( B acillariophyceae)
Author(s) -
Kamikawa Ryoma,
Yubuki Naoji,
Yoshida Masaki,
Taira Misaka,
Nakamura Noriaki,
Ishida Kenichiro,
Leander Brian S.,
Miyashita Hideaki,
Hashimoto Tetsuo,
Mayama Shigeki,
Inagaki Yuji
Publication year - 2015
Publication title -
phycological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.438
H-Index - 44
eISSN - 1440-1835
pISSN - 1322-0829
DOI - 10.1111/pre.12072
Subject(s) - plastid , biology , thylakoid , phylogenetic tree , photosynthesis , botany , phylogenetics , monophyly , ribosomal rna , evolutionary biology , chloroplast , gene , genetics , clade
Summary In order to obtain insights into the evolution of colorless (apochlorotic) diatoms, we investigated newly established apochlorotic strains of N itzschia spp. using light and electron microscopy and molecular phylogenetic analyses. Fluorescence 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 apochlorotic diatoms. The eight apochlorotic lineages were not monophyletic, suggesting that the loss of photosynthesis took place multiple times independently within N itzschia . Several diatoms, including N itzschia 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.