Scientists Sequence Genome of Coast Redwood

Researchers have successfully sequenced, assembled and annotated the genome of coast redwood (Sequoia sempervirens), one of the most widely recognized and iconic tree species on Earth.

Coast redwood is an evergreen tree reaching up to 115.5 m (379 feet) in height and living up to 2,200 years.

Also known as coastal redwood and California redwood, it the only living species of the genus Sequoia in the family Cupressaceae.

Coast redwood is considered ‘Endangered’ by the IUCN Red List. Its natural range is found primarily along the northern California Pacific Ocean coastline, although coast redwood trees have been planted all over the world.

Each of its two closest relatives, giant sequoia (Sequoiadendron giganteum) and dawn redwood (Metasequoia glyptostroboides), is also the only living member of its genus.

Coast redwood forests were extensively logged (nearly 95% of virgin forest) following immigration of Europeans into California.

There is currently strong interest in accelerating the return of old-growth forest characteristics including a diverse forest structure with large-stature trees.

Restoration and conservation efforts rely critically on the ability to measure and monitor genetic variation.

The ability to interrogate genomic regions under selection and estimate adaptive genetic diversity requires genetic markers from protein-coding regions of the genome.

Such markers have not existed for coast redwood and can only be developed following transcriptome or whole-genome sequencing.

“Our work on the coast redwood and giant sequoia genomes will enable us to develop modern genetic tools that can be used in the restoration and conservation of these ecologically important tree species,” said Professor David Neale, a researcher in the Department of Plant Sciences at the University of California, Davis.

Nearly nine times larger than the human genome, the redwood genome has 26.5 billion base pairs of DNA, and it is hexaploid, meaning redwoods have six sets of chromosomes. Humans have 3 billion base pairs of DNA and are diploid, with two sets of chromosomes.

The redwood genome is also the second largest genome sequenced.

When comparing the coast redwood genome sequence to that of other conifers, the researchers found hundreds of gene families unique to the coast redwood. Many are genes that help the trees respond to and fight stress, resist disease and repair after injury.

“This ambitious scientific research provides a critical foundation for Save the Redwoods League and the entire redwoods community,” said Dr. Joanna Nelson, director of science and conservation planning for Save the Redwoods League.

“It will ultimately help us understand the incredible range of responses that coast redwood and giant sequoia species have exhibited in the face of climate change and how native genetic diversity has informed these responses.”

“The Redwood Genome Project helps us see, for the first time, the full genetic diversity that has allowed these forests to adapt and survive for millennia — and could protect them against a suite of conditions they have never experienced.”

The team’s results were published in the journal G3: Genes, Genomes, Genetics.

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David B. Neale et al. Assembled and annotated 26.5 Gbp coast redwood genome: a resource for estimating evolutionary adaptive potential and investigating hexaploid origin. G3: Genes, Genomes, Genetics, publihsed online December 14, 2021; doi: 10.1093/g3journal/jkab380