The Y-segment of novel cold dehydrin genes is conserved and codons in the PR-10 genes are under positive selection in Oxytropis (Fabaceae) from contrasting climates |
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Authors: | Annie Archambault Martina V Str?mvik |
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Institution: | (1) Department of Plant Science, McGill University, 21111 Lakeshore Road, Sainte-Anne-de-Bellevue, QC, H9X3V9, Canada;(2) Present address: Department of Biology, Quebec Center for Biodiversity Science, McGill University, Stewart Biology Building, 1205 Dr. Penfield Avenue, Montreal, QC, H3A 1B1, Canada |
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Abstract: | While the arctic flora is particularly threatened by climate changes, the molecular aspects allowing colonization of this
harsh environment remain largely enigmatic. Genes with a likely functional or evolutive role for arctic Oxytropis (Fabaceae) were previously discovered given a sharp differential expression between arctic and temperate species, but the
evolutionary forces in action were unknown within the respective species. Here, we analyze gene duplication patterns and positive
and negative selection between genes from species of contrasting environments, which can reveal potential gene functions.
Genes were amplified and sequenced from two arctic (Oxytropis arctobia and O. maydelliana) and two temperate (O. campestris subsp. johannensis and O. splendens) species. Detection of codons under positive or negative selection and phylogenetic analyses were used to further elucidate
pathogenesis-related class 10 (PR-10), ripening-related proteins, cold dehydrins gene families and light-harvesting complex
(lhcaIII and lhcbI) genes from Oxytropis. Overall, results showed that the three gene families duplicated in tandem prior to the Oxytropis genus diversification; that genes overexpressed in arctic species evolve under higher constraints at the sequence level in
these species; that evolving novel protein variants in PR-10 genes were required for initial adaptation to the Arctic, and
that Oxytropis cold dehydrins are of a novel (K-like–Y4–K–S) structure, where the Y-segment is under stringent evolutive constraints in the arctic species. This suggests a scenario
not previously described for arctic plants, where tandem duplications precede gene recruitment that later become both highly
expressed and under stringent constraints in the arctic species. |
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