Genomic perspective for understanding ecological adaptability in oaks
image: Positively selected gene analysis of Quercus (A) Phylogenetic tree of deciduous-related species and evergreen species. The Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway enrichment analysis of positively selected genes in (B) deciduous Quercus with evergreen Quercus as background branches and (C) evergreen Quercus with deciduous Quercus as background branches (D) Model representing a simplified overview of the multiple pathways between environmental input signals and dormancy regulation and growth based on information gathered from annuals and perennials.
Credit: WANG ET AL.
Main text:
Oak (Quercus) is one of the most important taxa in the Northern Hemisphere in terms of its ecological, economical and cultural aspects. As a speciose and widely distributed tree genera, with approximately 450 species, oaks have exhibited remarkable adaptability to drought, cold and diverse environmental stress across different habitats. Nonetheless, it remains largely unclear how oaks evolved to exhibit such extensive ecological adaptability, particularly regarding the differences in adaptive evolution among various oak species.
In a study published in the KeAi journal Plant Diversity, a research group led by Yi-Gang Song from the College of Forestry and Biotechnology at Zhejiang A&F University, China, used a newly sequenced genome Quercus gilva, along with 18 previously published genomes, and RNA-seq data from leaves and other tissues of five oaks to assess the degree of genomic conservation, stability and the genomic footprints that underpin ecological adaptability in oaks.
“Many studies have explored the ecological adaptation footprints of tree species by assessing genetic variations associated with climate variables and evaluating millions of genomic variants within a single species. However, focusing solely on a single species may not fully capture the extensive and profound impacts of global climate change on species, communities and even ecosystems,” explains Song. “Investigating the genomic sequences of multiple closely related species can provide crucial insights into biological factors such as evolutionary history, genome evolution and functional gene identification, allowing us to clarify the foundation of species’ ecological adaptations."
In particular, the researchers found that oak species demonstrated a high degree of genomic conservation and stability, as indicated by the absence of large-scale chromosomal structural variations or additional whole-genome duplication events.
“The expansion and tandem duplication of gene families related to plant physical and chemical defense mechanisms, including cuticle biosynthesis and oxidosqualene cyclase genes, provided the foundation for the ecological adaptation of oak species,” shares Song. “Additionally, genes associated with circadian rhythm and hormone regulation may influence the ecological habits of evergreen and deciduous oaks.”
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Contact the author: Yi-Gang Song, ygsong@cemps.ac.cn
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