Adaptive sequence evolution is driven by biotic stress in a pair of orchid species (Dactylorhiza) with distinct ecological optima

Francisco Javier Balao Robles, Emiliano Trucchi, Thomas M Wolfe, Bao-Hai Hao, Maria Teresa Lorenzo, Juliane Baar, Laura Sedman, Carolin Kosiol, Fabian Amman, Mark W Chase, Mikael Hedrén, Ovidiu Paun

Publications: Contribution to journalArticlePeer Reviewed

Abstract

The orchid family is the largest in the angiosperms, but little is known about the molecular basis of the significant variation they exhibit. We investigate here the transcriptomic divergence between two European terrestrial orchids, Dactylorhiza incarnata and Dactylorhiza fuchsii, and integrate these results in the context of their distinct ecologies that we also document. Clear signals of lineage-specific adaptive evolution of protein-coding sequences are identified, notably targeting elements of biotic defence, including both physical and chemical adaptations in the context of divergent pools of pathogens and herbivores. In turn, a substantial regulatory divergence between the two species appears linked to adaptation/acclimation to abiotic conditions. Several of the pathways affected by differential expression are also targeted by deviating post-transcriptional regulation via sRNAs. Finally, D. incarnata appears to suffer from insufficient sRNA control over the activity of RNA-dependent DNA polymerase, resulting in increased activity of class I transposable elements and, over time, in larger genome size than that of D. fuchsii. The extensive molecular divergence between the two species suggests significant genomic and transcriptomic shock in their hybrids and offers insights into the difficulty of coexistence at the homoploid level. Altogether, biological response to selection, accumulated during the history of these orchids, appears governed by their microenvironmental context, in which biotic and abiotic pressures act synergistically to shape transcriptome structure, expression and regulation.

Original languageEnglish
Pages (from-to)3649-3662
Number of pages14
JournalMolecular Ecology
Volume26
Issue number14
DOIs
Publication statusPublished - Jul 2017

Austrian Fields of Science 2012

  • 106012 Evolutionary research
  • 106003 Biodiversity research
  • 106044 Systems biology

Keywords

  • Journal Article
  • ecological divergence
  • defence
  • transcriptomics
  • positive selection
  • abiotic stress
  • small RNAs

Cite this