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Phylogenetic analyses suggest lateral gene transfer from the mitochondrion to the apicoplast
Miroslav Oborník1, Yves Van de Peer, Václav Hypsa
1Institute of Parasitology, Czech Academy of Sciences, Branisovská 31, 370 05, Ceské Budejovice, Czech Republic. obornik@paru.cas.cz
Abstract:
Apicomplexan protozoa contain a single mitochondrion and a multimembranous plastid-like organelle termed apicoplast. The size of the apicomplexan plastid genome is extremely small (35 kb) thus offering a limited number of genes for phylogenetic analysis. Moreover, the sequences of apicoplast genes are highly adenosine+thymidine-rich and rapidly evolving. Due to these facts, phylogenetic analyses based on different genes or the structure of the ribosomal operon show conflicting results and the evolutionary history of this exciting organelle remains unclear. Although it is evident that the apicoplast and its genome is plastid-derived, our detailed phylogenetic analysis of amino acid and nucleotide sequences of selected apicoplast ribosomal protein genes rpl2, rpl14 and rps12 show their possible mitochondrial origin. The affinity of apicoplast ribosomal proteins to their mitochondrial homologs is very stable and well supported. Based on our results we propose that apicoplasts might contain both plastid and mitochondrial genes, thus constituting a hybrid assembly.
Insights
Apicoplasts, crucial organelles in apicomplexan parasites, may possess a hybrid genetic makeup. Phylogenetic analysis suggests some apicoplast genes might originate from mitochondria, not just plastids.
Area of Science:
- * Molecular Biology
- * Parasitology
- * Evolutionary Biology
Background:
- * Apicomplexan protozoa possess a mitochondrion and an apicoplast, a plastid-like organelle.
- * The apicoplast genome is small (35 kb), AT-rich, and rapidly evolving, complicating phylogenetic analysis.
- * Previous studies indicate apicoplasts are plastid-derived, but their evolutionary history remains debated due to conflicting phylogenetic results.
Purpose of the Study:
- * To investigate the evolutionary origin of apicoplast ribosomal protein genes.
- * To clarify the phylogenetic relationships of apicoplast genes.
- * To determine if apicoplasts contain genes of mitochondrial origin.
Main Methods:
- * Detailed phylogenetic analysis of amino acid and nucleotide sequences.
- * Focus on specific apicoplast ribosomal protein genes: rpl2, rpl14, and rps12.
- * Comparison of apicoplast gene sequences with homologous mitochondrial and plastid genes.
Main Results:
- * Phylogenetic analysis revealed stable and well-supported affinity between apicoplast ribosomal proteins and their mitochondrial homologs.
- * Conflicting results from previous studies using different genes or ribosomal operon structures highlight the complexity.
- * The data suggests a potential mitochondrial origin for some apicoplast genes, challenging the purely plastid-derived model.
Conclusions:
- * Apicoplasts may represent a hybrid organelle, incorporating genes from both plastid and mitochondrial ancestries.
- * The evolutionary history of the apicoplast is more complex than previously understood.
- * This finding necessitates a re-evaluation of organelle evolution and gene transfer mechanisms in eukaryotes.