Journal Article

Evolutionary Insights on C<sub>4</sub> Photosynthetic Subtypes in Grasses from Genomics and Phylogenetics

Pascal-Antoine Christin, Emanuela Samaritani, Blaise Petitpierre, Nicolas Salamin and Guillaume Besnard

in Genome Biology and Evolution

Published on behalf of Society for Molecular Biology and Evolution

Volume 1, issue , pages 221-230
Published in print January 2009 |
Published online July 2009 | e-ISSN: 1759-6653 | DOI: http://dx.doi.org/10.1093/gbe/evp020

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In plants, an oligogene family encodes NADP-malic enzymes (NADP-me), which are responsible for various functions and exhibit different kinetics and expression patterns. In particular, a chloroplast isoform of NADP-me plays a key role in one of the three biochemical subtypes of C4 photosynthesis, an adaptation to warm environments that evolved several times independently during angiosperm diversification. By combining genomic and phylogenetic approaches, this study aimed at identifying the molecular mechanisms linked to the recurrent evolutions of C4-specific NADP-me in grasses (Poaceae). Genes encoding NADP-me (nadpme) were retrieved from genomes of model grasses and isolated from a large sample of C3 and C4 grasses. Genomic and phylogenetic analyses showed that 1) the grass nadpme gene family is composed of four main lineages, one of which is expressed in plastids (nadpme-IV), 2) C4-specific NADP-me evolved at least five times independently from nadpme-IV, and 3) some codons driven by positive selection underwent parallel changes during the multiple C4 origins. The C4 NADP-me being expressed in chloroplasts probably constrained its recurrent evolutions from the only plastid nadpme lineage and this common starting point limited the number of evolutionary paths toward a C4 optimized enzyme, resulting in genetic convergence. In light of the history of nadpme genes, an evolutionary scenario of the C4 phenotype using NADP-me is discussed.

Keywords: gene duplication; molecular convergence; evolutionary constraint; genetic adaptation; multiple origins

Journal Article.  6559 words.  Illustrated.

Subjects: Bioinformatics and Computational Biology ; Evolutionary Biology ; Genetics and Genomics

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