Conifer ancestors had a double dose of DNA

Douglas fir trees in Bryce Canyon

Ancestors of  Douglas firs (Pseudotsuga menziesii), such as this one growing in Bryce Canyon National Park, and other conifers underwent genome duplication — adding extra copies of genetic material — around the time of the Permian-Triassic extinction.

Zheng Li

Conifers grew giant genomes thanks to double doses of genetic material.

Ancient ancestors of today’s pine, cypress and yew trees had extra copies of their entire genome — the set of genetic instructions for an organism, researchers report November 20 in Science Advances.  

Whole genome duplications are common among plants, but a previous examination of Norway spruce DNA didn’t find evidence of such doubling in conifers. The new study examined the transcriptomes — the entire set of active genes in an organism — of 24 conifers and other seed plants and three distantly related plants.

In ancestors of cypress (Cupressaceae) and yew (Taxaceae) trees, genome duplication occurred about 210 to 275 million years ago, Michael Barker of the University of Arizona in Tucson and colleagues calculate. Such DNA multiplication occurred in trees in the pine family (Pinaceae) about 200 to 342 million years ago. The extra DNA may have helped conifers survive the Permian-Triassic extinction about 252 million years ago, the researchers speculate.

Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.

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