Comparative transcriptomics reveals lineage specific evolution of cold response in Pooideae

Abstract

BackgroundUnderstanding how complex traits evolve through adaptive changes in gene regulation remains a major challenge in evolutionary biology. Over the last ~50 million years, Earth has experienced climate cooling and ancestrally tropical plants have adapted to expanding temperate environments. The grass subfamily Pooideae dominates the grass flora of the temperate regions, but the role of cold-response gene regulation in the transitioning from tropical to temperate climate remains unexplored.\n\nResultsTo establish if molecular responses to cold are conserved throughout the phylogeny, we assembled the transcriptomes of five Pooideae species spanning early to later diverging lineages, and compared short- and long-term cold responsive genes using 8633 high confidence ortholog groups with resolved gene tree topologies. We found that a majority of cold responsive genes were specific to one or two lineages, an observation that we deem incompatible with a cold adapted Pooideae ancestor. However, all five species shared short-term cold response in a small set of general stress genes as well as the ability to down-regulate the photosynthetic machinery during cold temperatures.\n\nConclusionsOur observations indicate that the different Pooideae lineages have assembled cold response programs in parallel by taking advantage of a common potential for cold adaptation.