Comparative Genomics of Spruce and Other Gymnosperms

In contrast to flowering plants, the genomes of gymnosperms are still poorly understood. Current knowledge on the genomic architecture, gene space, and macrostructure of gymnosperm genomes mainly comes from Pinaceae species, in which spruce species (genera with most sequenced genomes to date) had played a significant role. Whereas the accumulation of nuclear genomes’ sequence information has followed a slow pace, the sequencing of chloroplast genomes skyrocketed in the last 10 years, with many spruce species sequenced so far. From the comparison of nuclear, mitochondrial, and chloroplast genomes, we can conclude that they all differ in their genomic macrostructure and rates of sequence evolution. The high structural conservation among species, genera, and families is characteristic of nuclear genomes, whereas chloroplast and mitochondrial genomes show less conserved structures due to genomic arrangements. Finally, Picea species follow trends observed in other gymnosperms and angiosperms, in which rates of sequence evolution are the highest in nuclear DNA, followed by chloroplast and then mitochondrial DNA.