32,000-year-old Seeds Brought Back to Life

One of the most intriguing stories in Paleoethnobotany is that of the oldest plant ever to be “resurrected” grown from 32,000-year-old seeds found from ancient squirrel burrows.

A team of scientists from the Institute of Cell Biophysics and the Institute of Physicochemical and Biological Problems in Soil Science, of the Russian Academy of Sciences, successfully revived a flowering plant from a 32,000-year-old fruit buried in Siberian permafrost.

Fruiting (at left) and flowering plants of Silene stenophylla regenerated from tissue of fossil fruits (S. Yashina et al)

Reviving the story of 2007, when a team of scientists from Russia, Hungary and the United States recovered frozen Silene stenophylla seeds and remains from the Pleistocene era, while investigating about 70 ancient ground squirrel hibernation burrows or caches, hidden in permanently frozen loess-ice deposits in north eastern Siberia, in the plant’s present-day range.

In a study, published in the Proceedings of the National Academy of Sciences, the scientists describe how they regenerated fertile plants of Silene stenophylla from fruit tissue of Late Pleistocene age using in vitro tissue culture and clonal micropropagation techniques.

Commonly called narrow-leafed campion, S. stenophylla is an extant species of flowering plant in the family Caryophyllaceae. Its seeds and fruits dating back to the last Ice Age were excavated from fossil burrows of an Arctic species of ground squirrel (Urocitellus parryii).

The scientists discovered about 70 prehistoric storage chambers of this squirrel species in 2007 at depths of 20–40 m below the present day surface in permanently frozen loess-ice deposits on the right bank of lower Kolyma River, northeastern Siberia. These chambers contained a great supply of various plant seeds and fruits. In some of them, the number of seeds and fruits reached up to 600–800 thousands.

“Several immature fruits were found at a depth of 38 m in a seed conglomerate from the Duvanny Yar burrow,” the team wrote in the paper. “Silene seeds and fruits were dominant in this burrow and were in a state of good morphological preservation. Radiocarbon dating showed them to be 31,800 years old.”

Using in vitro tissue culture method, adopted for the regeneration of ancient plants, and microclonal propagation technique, the team was able to grow 36 ancient plants from fragments of the placental tissue of three immature uninjured fruits of S. stenophylla.

Immature fruit of Silene stenophylla from burrow buried in permafrost more than 30,000 y ago. (A) Dissected fruit showing seeds and placenta (P). (B) Fragment of placenta with seeds at different developmental stages. (Scale bars, 1 mm.)

Then the scientists tested the plants for their sexual fertility: “It should be noted that S. stenophylla is allogamous and requires cross-fertilization for sexual reproduction to occur. Flowers of the ancient plants were pollinated artificially using pollen from other ancient plants, pollination of extant plants was performed similarly. The time from artificial pollination of flowers to ripening of first seeds took 8–9 weeks. Laboratory germination of seeds taken from regenerated ancient plants was 100 %.”


Clonal micropropagation of Silene stenophylla regenerated from placenta tissue of immature 30,000-y-old fruits buried in permafrost deposits. (А) Initial shoot initiated from placental tissue in vitro. (В) Stages of clonal micropropagation from primary shoots to rooted plants. (Scale bars, 20 mm.)

The taxonomic identification of both ancient and extant plants revealed that they are distinct phenotypes of S. stenophylla.

The team claims that the regenerated plants of S. stenophylla are now the most ancient, viable, multicellular, living organisms. The previous record-holder is a date palm derived from a 2,000-year-old seed recovered from the ancient fortress of Masada in Israel.

Sources

Sci-News

Proc Natl Acad Sci U S A

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