The Norway spruce genome sequence and conifer genome evolution. Conifers, which have dominated forests for over 200 million years, are ecologically and economically important. This study presents the first draft genome sequence of a gymnosperm, the Norway spruce (Picea abies), with a genome size of 20 gigabases. The number of well-supported genes is similar to that of Arabidopsis thaliana, despite the much larger genome size. The large genome size is attributed to the accumulation of long-terminal repeat transposable elements, possibly due to a lack of efficient elimination mechanisms. Comparative sequencing of other conifers revealed shared transposable element diversity. Expression of 24-nucleotide small RNAs, involved in transposable element silencing, is tissue-specific and lower than in other plants. The genome contains numerous long introns, gene-like fragments, long non-coding RNAs, and short RNAs, opening new genomic avenues for conifer forestry and breeding. Gymnosperms include conifers, cycads, Ginkgo, and gnetophytes. Conifers first appeared over 300 million years ago, before the angiosperm lineage diverged. Conifer families radiated 250–65 million years ago, with relatively little morphological change. Conifers are dominant in many terrestrial ecosystems, especially in the Northern Hemisphere. They have survived major mass extinction events. Conifers are ecologically and economically valuable, contributing significantly to terrestrial photosynthesis and biomass. However, our understanding of conifer genomes is limited. Most conifers have 12 chromosomes, with large genome sizes and high repetitive elements. Conifer genomes have not been well characterized, although some reports suggest larger gene families and numerous pseudogenes. Conifer genomes are among the largest, making genome-wide analyses challenging. No full genome sequence of a gymnosperm is available, while many angiosperm genomes have been sequenced. Conifer genomes are challenging to sequence due to their outbreeding nature, large effective population sizes, and high heterozygosity. Despite this, conifer genomes have lower nucleotide substitution rates than most angiosperms, possibly due to long lifespans. Inbreeding depression limits the production of inbred lines for genome assembly. The availability of conifer genome sequences would enable comparative analyses of genome architecture and the evolution of key traits in seed plants, including flower or fruit development and life history. This would help determine how and why conifer genomes became so large. To address these issues, the study assembled a draft of the 20-Gb nuclear genome of Norway spruce, one of the most widespread and ecologically and economically important plants in Europe. The genome was analyzed, and compared to the low-coverage draft genomes of five other gymnosperms. The study identified numerous long introns, gene-like fragments, long non-coding RNAs, and short RNAsThe Norway spruce genome sequence and conifer genome evolution. Conifers, which have dominated forests for over 200 million years, are ecologically and economically important. This study presents the first draft genome sequence of a gymnosperm, the Norway spruce (Picea abies), with a genome size of 20 gigabases. The number of well-supported genes is similar to that of Arabidopsis thaliana, despite the much larger genome size. The large genome size is attributed to the accumulation of long-terminal repeat transposable elements, possibly due to a lack of efficient elimination mechanisms. Comparative sequencing of other conifers revealed shared transposable element diversity. Expression of 24-nucleotide small RNAs, involved in transposable element silencing, is tissue-specific and lower than in other plants. The genome contains numerous long introns, gene-like fragments, long non-coding RNAs, and short RNAs, opening new genomic avenues for conifer forestry and breeding. Gymnosperms include conifers, cycads, Ginkgo, and gnetophytes. Conifers first appeared over 300 million years ago, before the angiosperm lineage diverged. Conifer families radiated 250–65 million years ago, with relatively little morphological change. Conifers are dominant in many terrestrial ecosystems, especially in the Northern Hemisphere. They have survived major mass extinction events. Conifers are ecologically and economically valuable, contributing significantly to terrestrial photosynthesis and biomass. However, our understanding of conifer genomes is limited. Most conifers have 12 chromosomes, with large genome sizes and high repetitive elements. Conifer genomes have not been well characterized, although some reports suggest larger gene families and numerous pseudogenes. Conifer genomes are among the largest, making genome-wide analyses challenging. No full genome sequence of a gymnosperm is available, while many angiosperm genomes have been sequenced. Conifer genomes are challenging to sequence due to their outbreeding nature, large effective population sizes, and high heterozygosity. Despite this, conifer genomes have lower nucleotide substitution rates than most angiosperms, possibly due to long lifespans. Inbreeding depression limits the production of inbred lines for genome assembly. The availability of conifer genome sequences would enable comparative analyses of genome architecture and the evolution of key traits in seed plants, including flower or fruit development and life history. This would help determine how and why conifer genomes became so large. To address these issues, the study assembled a draft of the 20-Gb nuclear genome of Norway spruce, one of the most widespread and ecologically and economically important plants in Europe. The genome was analyzed, and compared to the low-coverage draft genomes of five other gymnosperms. The study identified numerous long introns, gene-like fragments, long non-coding RNAs, and short RNAs