title: Fundamental shift in vitamin B12 eco-physiology of a model alga demonstrated by experimental evolution.
abstract: A widespread and complex distribution of vitamin requirements exists over the entire tree of life, with many species having evolved vitamin dependence, both within and between different lineages. Vitamin availability has been proposed to drive selection for vitamin dependence, in a process that links an organism's metabolism to the environment, but this has never been demonstrated directly. Moreover, understanding the physiological processes and evolutionary dynamics that influence metabolic demand for these important micronutrients has significant implications in terms of nutrient acquisition and, in microbial organisms, can affect community composition and metabolic exchange between coexisting species. Here we investigate the origins of vitamin dependence, using an experimental evolution approach with the vitamin B(12)-independent model green alga Chlamydomonas reinhardtii. In fewer than 500 generations of growth in the presence of vitamin B(12), we observe the evolution of a B(12)-dependent clone that rapidly displaces its ancestor. Genetic characterization of this line reveals a type-II Gulliver-related transposable element integrated into the B(12)-independent methionine synthase gene (METE), knocking out gene function and fundamentally altering the physiology of the alga.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Cambridge, UK.
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Helliwell
authors.affiliation: Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Sinéad
authors.initials: S
authors.lastname: Collins
authors.affiliation: Department of Plant Sciences, University of Cambridge, Cambridge, UK.
authors.forename: Elena
authors.initials: E
authors.lastname: Kazamia
authors.affiliation: Institute of Structural and Molecular Biology, UCL, London, UK.
authors.forename: Saul
authors.initials: S
authors.lastname: Purton
authors.affiliation: 1] Plymouth Marine Laboratory, Plymouth, UK [2] Marine Biological Association of UK, The Laboratory, Citadel Hill, Plymouth, UK.
authors.forename: Glen L
authors.initials: GL
authors.lastname: Wheeler
authors.affiliation: Department of Plant Sciences, University of Cambridge, Cambridge, UK.
authors.forename: Alison G
authors.initials: AG
authors.lastname: Smith
mesh_terms: D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000235:genetics* / Q000378:metabolism; D005075:Biological Evolution; D016825:Chlamydomonas reinhardtii / Q000201:enzymology / Q000235:genetics*; D018920:Coculture Techniques; D004251:DNA Transposable Elements; D018977:Micronutrients; D009154:Mutation; D010641:Phenotype; D014805:Vitamin B 12 / Q000378:metabolism*; D014803:Vitamin B Complex
chemical_list: D004251:DNA Transposable Elements; D018977:Micronutrients; D014803:Vitamin B Complex; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D014805:Vitamin B 12