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Zombie Moss?

In the year 450 A.D., Attila the Hun was invading Europe, the last of the Roman empire was crumbling (including the abandonment of Londinium), the Aztec civilization in Mexico was just beginning, and a little moss plant (a bryophyte) was growing on Signy, a small subantarctic island.

Now fast-forward 1,564 years to the present day.

Small remnants of this moss plant, frozen in permafrost for over 1,500 years, are reportedly being regenerated in a laboratory at the University of Reading, in southern England, about 25 miles west of London.

In a recent report (see Ref. 1 below), researchers from the U.K. and New Zealand have broken the previous age record (about 400 years – see Ref. 2 below) for regeneration of intact, multicellular organisms from frozen environments. According to these scientists “…we show unprecedented millennial-scale survival and viability deep within an Antarctic moss bank preserved in permafrost.” (from: Ref. 1 below)

Here’s a brief (about 1 minute) YouTube video summarizing this report:

The mosses regenerated from core samples were carbon-dated to be at least 1,500 years old. But these aren’t even the oldest parts of the Signy Island frozen moss banks, which may be over 5,000 years old. Could mosses that were growing on Signy Island during the time of the construction of the Great Pyramid of Giza, about 2,600 B.C., be revived from frozen specimens? These researchers speculate that this may indeed be possible. (see Ref. 1 below)

But wait a minute? Haven’t 5,000-year-old seeds from ancient Egyptian tombs been germinated and revived?

Nope. This is a myth.

But what’s apparently not a myth is the regeneration of 1,500-year-old frozen moss plants. And it also should be mentioned that the successful regeneration of whole, fertile plants from small pieces of 30,000-year-old frozen fruit tissue using plant tissue culture has been reported. (Please see Ref. 3 below.)

How can intact moss plants remain viable for over a thousand years in permafrost? And how can frozen plant cells apparently remain viable even after 30,000 years in permafrost?

The (probable) answer is:

Cryptobiosis

Over fifty years ago, “David Keilin (Proc. Roy. Soc. Lond. B, 150, 1959, 149–191) coined the term “cryptobiosis” (hidden life) and defined it as “the state of an organism when it shows no visible signs of life and when its metabolic activity becomes hardly measurable, or comes reversibly to a standstill.”” and “Keilin noted that cryptobiosis resulted from such things as desiccation (anhydrobiosis), low temperature (cryobiosis), lack of oxygen (anoxybiosis) or combinations of these.” (from Ref. 4 below)

Though most of the reported research regarding cryptobiosis appears to have been conducted on tardigrades, the preservation of viable plant material in permafrost is likely due not only to cryobiosis but also to anoxybiosis and, especially, to desiccation.

Some mosses are well-known to be able tolerate drought and desiccation, and the cellular and molecular mechanisms responsible for this have been been studied (see Ref. 5, for example).

The desiccation tolerance of mosses likely involves both the accumulation of increased solutes (such as sucrose) and the production of protective proteins such as dehydrins in order to preserve cellular structures and also to aid in the recovery of the cells upon rehydration.

It wouldn’t be surprising if we find that the mosses revived after more than 1,500 years in permafrost relied on many of the same survival strategies that the desiccation-tolerant mosses use.

References

1. Roads, E., R. E. Longton and P. Convey (2014) “Millennial timescale regeneration in a moss from Antarctica.” Current Biology, Vol. 24, R222-R223, doi:10.1016/j.cub.2014.01.053. (Full Text)

2. La Farge, C., K. H. Williams, and J. H. England (2013) “Regeneration of Little Ice Age bryophytes emerging from a polar glacier with implications of totipotency in extreme environments.” Proc. Natl. Acad. Sci. (USA), Vol. 110, pp.9839–9844. (Full Text)

3.Yashina, S., et al. (2012) “Regeneration of whole fertile plants from 30,000-y-old fruit tissue buried in Siberian permafrost.” Proc. Natl. Acad. Sci. (USA), Vol. 109, pp. 4008–4013. (Full Text)

4. Clegg, J. S. (2001) “Cryptobiosis – a peculiar state of biological organization.” Comparative Biochemistry and Physiology, Part B, Vol. 128, pp. 613-624. (PDF).

5. Charron, A. J. and R. S. Quatrano (2009) “Between a Rock and a Dry Place: The Water-Stressed Moss.” Molecular Plant, Vol. 2, pp. 478-486. (Full Text)

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