From genotypes to phenotypes: expression levels of genes encompassing adaptive SNPs in black spruce

Tackling the challenges of evolutionary forest research with multidata approaches

Many forest tree species have characteristics that make the study of their evolutionary ecology complex. For example, they are long-lived and thus have long generation times, and their often large, complex genomes have hampered establishing genomic resources. One way to tackle this challenge is to access multiple complementary data sources and analytical approaches when attempting to infer patterns of adaptive evolution. In the cover article of this issue of Molecular Ecology, Depardieu et al. (2021) combine large amounts of environmental, genomic, dendrochronological, and gene expression data in a common garden to explore the polygenic basis of drought resistance in white spruce (Picea glauca), a long-lived conifer. They identify candidate genes involved in growth and resistance to extreme drought events and show how multiple data sets may deliver complementary evidence to circumvent the manifold challenges of the research field.

Connecting tree-ring phenotypes, genetic associations and transcriptomics to decipher the genomic architecture of drought adaptation in a widespread conifer

As boreal forests face significant threats from climate change, understanding evolutionary trajectories of coniferous species has become fundamental to adapting management and conservation to a drying climate. We examined the genomic architecture underlying adaptive variation related to drought tolerance in 43 populations of a widespread boreal conifer, white spruce (Piceaglauca [Moench] Voss), by combining genotype–environment associations, genotype–phenotype associations, and transcriptomics. Adaptive genetic variation was identified by correlating allele frequencies for 6,153 single nucleotide polymorphisms from 2,606 candidate genes with temperature, precipitation and aridity gradients, and testing for significant associations between genotypes and 11 dendrometric and drought‐related traits (i.e., anatomical, growth response and climate‐sensitivity traits) using a polygenic model. We identified a set of 285 genes significantly associated with a climatic factor or a phenotypic trait, including 110 that were differentially expressed in response to drought under greenhouse‐controlled conditions. The interlinked phenotype–genotype–environment network revealed eight high‐confidence genes involved in white spruce adaptation to drought, of which four were drought‐responsive in the expression analysis. Our findings represent a significant step toward the characterization of the genomic basis of drought tolerance and adaptation to climate in conifers, which is essential to enable the establishment of resilient forests in view of new climate conditions.

see also the Perspective by Lars Opgenoorth and Christian Rellstab