Iron-Sulfur Cluster Biosynthesis in Algae with Complex Plastids

Genome Biol Evol. 2018 Aug 1;10(8):2061-2071. doi: 10.1093/gbe/evy156.

Abstract

Plastids surrounded by four membranes harbor a special compartment between the outer and inner plastid membrane pair, the so-called periplastidal compartment (PPC). This cellular structure is usually presumed to be the reduced cytoplasm of a eukaryotic phototrophic endosymbiont, which was integrated into a host cell and streamlined into a plastid with a complex membrane structure. Up to date, no mitochondrion or mitochondrion-related organelle has been identified in the PPC of any representative. However, two prominent groups, the cryptophytes and the chlorarachniophytes, still harbor a reduced cell nucleus of symbiont origin, the nucleomorph, in their PPCs. Generally, many cytoplasmic and nucleus-located eukaryotic proteins need an iron-sulfur cofactor for their functionality. Beside some exceptions, their synthesis is depending on a so-called iron-sulfur complex (ISC) assembly machinery located in the mitochondrion. This machinery provides the cytoplasm with a still unknown sulfur component, which is then converted into iron-sulfur clusters via a cytosolic iron-sulfur protein assembly (CIA) machinery. Here, we investigated if a CIA machinery is present in mitochondrion-lacking PPCs. By using bioinformatic screens and in vivo-localizations of candidate proteins, we show that the presence of a PPC-specific CIA machinery correlates with the presence of a nucleomorph. Phylogenetic analyses of PPC- and host specific CIA components additionally indicate a complex evolution of the CIA machineries in organisms having plastids surrounded by four membranes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Compartmentation
  • Cryptophyta / genetics
  • Cryptophyta / metabolism*
  • Cytosol / metabolism
  • Diatoms / genetics
  • Genome
  • Iron-Sulfur Proteins / biosynthesis*
  • Models, Biological
  • Phylogeny
  • Plastids / metabolism*

Substances

  • Iron-Sulfur Proteins