Elsevier

Microbiological Research

Volume 243, February 2021, 126649
Microbiological Research

The plastid proteome of the nonphotosynthetic chlorophycean alga Polytomella parva

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Highlights

  • The Polytomella parva plastid proteome is represented by 309 proteins.

  • This is the first plastid proteome of a nonphotosynthetic, free-living alga.

  • This proteome depicts the minimal metabolism for plastid functioning.

  • The plastid preserves some components of the chloroplast translocation machinery.

  • Insights on how algal chloroplasts morphed into colorless plastids are provided.

Abstract

The unicellular, free-living, nonphotosynthetic chlorophycean alga Polytomella parva, closely related to Chlamydomonas reinhardtii and Volvox carteri, contains colorless, starch-storing plastids. The P. parva plastids lack all light-dependent processes but maintain crucial metabolic pathways. The colorless alga also lacks a plastid genome, meaning no transcription or translation should occur inside the organelle. Here, using an algal fraction enriched in plastids as well as publicly available transcriptome data, we provide a morphological and proteomic characterization of the P. parva plastid, ultimately identifying several plastid proteins, both by mass spectrometry and bioinformatic analyses. Data are available via ProteomeXchange with identifier PXD022051. Altogether these results led us to propose a plastid proteome for P. parva, i.e., a set of proteins that participate in carbohydrate metabolism; in the synthesis and degradation of starch, amino acids and lipids; in the biosynthesis of terpenoids and tetrapyrroles; in solute transport and protein translocation; and in redox homeostasis. This is the first detailed plastid proteome from a unicellular, free-living colorless alga.

Keywords

Nonphotosynthetic algae
Polytomella parva
Chlorophycean algae
Chlamydomonas reinhardtii
Amyloplast
Plastid proteome

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