Paleolithic Park

March 6, 2012 § Leave a comment

Perhaps not quite as exciting as revivified dinosaurs, but still amazing: plants from the late Paleolithic era are claimed to have been regenerated from fossil material (Yashina et al. 2012. Regeneration of whole fertile plants from 30,000-y-old fruit tissue buried in Siberian permafrost.  PNAS doi:10.10.73/pnas.1118386109).  This has very little to do with systems biology, but I was interested and thought you would be too.  Perhaps I could trace some kind of connection (did you know that our Artist-no-longer-in-Residence, Brian Knep, shared two Academy Awards for his work on the movie Jurassic Park?) but it would be forced and hardly worth it.  Better to admit to mild frivolity.

The plant material in question came, not from an insect trapped in amber, but from fruits buried in burrows of an Arctic-dwelling squirrel.  Some of these burrows contain hundreds of thousands of fruits and seeds.  I guess when you’re a squirrel living in the Arctic, you grab what’s going while the grabbing is good.  Shortly after the squirrels stored their hoards, about 30,000 years ago, the area froze, was buried deep in icy sludge, and has never since melted.  Constant subzero temperatures, with all available water immobilized as ice, are the best conditions you’re likely to find for cryopreservation.  Although the oldest plant seed previously germinated was only 2,000 years old, the authors were bold enough to make an attempt to grow plants from ancient frozen seeds of the plant Silene stenophylla, the arctic campion.

The placental tissue in a campion fruit. From Yashina et al.

In the end, what Yashina et al. say that they were able to grow was not the seeds themselves but an outgrowth of the placental tissue some of the immature seeds were embedded in.  The authors speculate that part of the reason they were successful with this tissue is because it has especially high levels of organic substances such as sucrose and phenolic compounds that would be expected to offer some protection against frost damage.  The plants derived from these placental tissues grew to maturity and were even capable of breeding.  They look somewhat different from modern Silene stenophylla, and they handle their flowering arrangements differently; flowers of the modern plants are always bisexual, whereas the ancient plants produced female flowers first, followed by bisexual flowers.

Micropropagation of plants from ancient placental tissue. From Yashina et al. 2012.

Though previous claims that plants have been grown from very old seeds have been debunked, the authors say that because the burrows were buried ~20-40 meters down and were apparently undisturbed they are confident that their samples were not contaminated with modern seeds.  They also performed direct radiocarbon dating on their samples.  And the plants that resulted were visibly different from their modern counterparts.  It’ll be fascinating to see the DNA sequence; I’m sure it’s on its way.

Sadly, the last author of the paper, Dr. David Gilichinsky, died just 2 days before the paper was published.

Yashina, S., Gubin, S., Maksimovich, S., Yashina, A., Gakhova, E., & Gilichinsky, D. (2012). Regeneration of whole fertile plants from 30,000-y-old fruit tissue buried in Siberian permafrost Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1118386109

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