Occurrence, Evolution and Specificities of Iron-Sulfur Proteins and Maturation Factors in Chloroplasts from Algae

Abstract

Iron-containing proteins, including iron-sulfur (Fe-S) proteins, are essential for numerous electron transfer and metabolic reactions. They are present in most subcellular compartments. In plastids, in addition to sustaining the linear and cyclic photosynthetic electron transfer chains, Fe-S proteins participate in carbon, nitrogen, and sulfur assimilation, tetrapyrrole and isoprenoid metabolism, and lipoic acid and thiamine synthesis. The synthesis of Fe-S clusters, their trafficking, and their insertion into chloroplastic proteins necessitate the so-called sulfur mobilization (SUF) protein machinery. In the first part, we describe the molecular mechanisms that allow Fe-S cluster synthesis and insertion into acceptor proteins by the SUF machinery and analyze the occurrence of the SUF components in microalgae, focusing in particular on the green alga Chlamydomonas reinhardtii. In the second part, we describe chloroplastic Fe-S protein-dependent pathways that are specific to Chlamydomonas or for which Chlamydomonas presents specificities compared to terrestrial plants, putting notable emphasis on the contribution of Fe-S proteins to chlorophyll synthesis in the dark and to the fermentative metabolism. The occurrence and evolutionary conservation of these enzymes and pathways have been analyzed in all supergroups of microalgae performing oxygenic photosynthesis.

A cryptic plastid and a novel mitochondrial plasmid inLeucomyxa plasmidiferagen. and sp. nov. (Ochrophyta) push the frontiers of organellar biology

“…This is in a striking contrast with the presence of the SUF system in virtually all other plastids investigated, including those lacking any suf gene in their plastid genome (see also figure 3) and having the SUF system encoded fully by the nuclear genome. The latter concerns not only photosynthetic taxa (Przybyla-Toscano et al 2021), but also eukaryotes bearing non-photosynthetic plastids, such as the parasitic trebouxiophyte Helicosporidium sp. (Pombert et al 2014), various non-photosynthetic myzozoans (colpodellids, Perkinsus , Platyproteum ; Janouškovec et al 2015; Mathur et al 2019), or Euglena longa (Novák Vanclová et al 2020).…”

Iron uptake of etioplasts is independent from photosynthesis but applies the reduction-based strategy

“…Even though there was a declining tendency in the Fe content of isolated plastids as the degree of etiolation increased, Fe was still present even in the plastids of the fully etiolated Layer 5 leaves. Although photosynthetic machinery, especially PSI complexes, has the highest Fe requirements in plants, multiple other plastidial proteins, including those related to photosynthesis such as PETA, PETB, and PETC chains of the Cyt b 6 /f complex, NDHI and NDHK of the NDH complex, ferredoxins, chlorophyll cyclase CRD1/CHl27, 7-hydroxymethyl chlorophyll a reductase, as well as those primarily unrelated to photosynthesis such as Fe superoxide dismutase, ascorbate peroxidases, lipopoxygenases, adenosine 5′-phosphosulfate reductase, sulfite reductase, plastidial nitrate reductase, and glutamine:oxoglutarate aminotransferase, require Fe cofactors for proper functioning ( Hantzis et al., 2018 ; Lu, 2018 ; Kroh and Pilon, 2020 ; Przybyla-Toscano et al., 2021 ). Unlike Nicotiana clevelandii × N. glutinosa cotyledons ( Sprey et al., 1977 ), Fe accumulation in ferritin was not detected in the etioplasts of Savoy cabbage; thus, the biosynthesis of Fe-containing proteins relies on the continuous import of Fe into the plastids.…”

Chlamydomonas reinhardtii—A Reference Microorganism for Eukaryotic Molybdenum Metabolism

“…All of this has allowed for the development of a number of biochemical, metabolic, and physiological studies that have contributed to the understanding of the structure, function, and regulation of several biological processes [ 17 ]. Among others, the research topics that have used Chlamydomonas as a reference organism include the metabolism of nitrogen [ 18 ], sulfur [ 19 ], phosphorus [ 20 ], amino acid [ 21 ], and lipids [ 22 ], the biosynthesis of carotenoids [ 23 ], starch [ 24 ], heme groups [ 25 ], Fe-S clusters [ 26 ], chlorophyll [ 27 ], and glycerolipids [ 28 ], as well as the function of chaperones [ 29 ], proteases [ 30 ], thioredoxins [ 31 ], and flagella [ 32 ] and the response to different types of stresses [ 33 ].…”