Kapralov, Maxim V.Smith, J. Andrew C.Filatov, Dmitry A.2015-11-162015-11-161932-6203http://hdl.handle.net/1885/16497BACKGROUND Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) catalyses the key reaction in the photosynthetic assimilation of CO₂. In C₄ plants CO₂ is supplied to Rubisco by an auxiliary CO₂-concentrating pathway that helps to maximize the carboxylase activity of the enzyme while suppressing its oxygenase activity. As a consequence, C₄ Rubisco exhibits a higher maximum velocity but lower substrate specificity compared with the C₃ enzyme. Specific amino-acids in Rubisco are associated with C₄ photosynthesis in monocots, but it is not known whether selection has acted on Rubisco in a similar way in eudicots. METHODOLOGY/PRINCIPAL FINDINGS We investigated Rubisco evolution in Amaranthaceae sensu lato (including Chenopodiaceae), the third-largest family of C₄ plants, using phylogeny-based maximum likelihood and Bayesian methods to detect Darwinian selection on the chloroplast rbcL gene in a sample of 179 species. Two Rubisco residues, 281 and 309, were found to be under positive selection in C₄ Amaranthaceae with multiple parallel replacements of alanine by serine at position 281 and methionine by isoleucine at position 309. Remarkably, both amino-acids have been detected in other C₄ plant groups, such as C₄ monocots, illustrating a striking parallelism in molecular evolution. CONCLUSIONS/SIGNIFICANCE Our findings illustrate how simple genetic changes can contribute to the evolution of photosynthesis and strengthen the hypothesis that parallel amino-acid replacements are associated with adaptive changes in Rubisco.This research was funded by NERC (http://www.nerc.ac.uk/; grant number NE/H007741/1).8 pages© 2012 Kapralov et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.amaranthaceaebase sequencegenes, plantmolecular sequence dataphotosynthesisphylogenyribulose-bisphosphate carboxylaseribulosephosphatesselection, geneticevolution, molecular2012-12-2010.1371/journal.pone.00529742015-12-10