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New record size for a genome goes to rare plant

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paris japonica plant largest genomeA rare plant called Paris japonica has a genome 50 times longer than that of humans, making it the longest genome ever recorded. The Royal Botanic Gardens, Kew, announced the discovery last week, and details appear in the September 2010 issue of the Botanical Journal of the Linnean Society.

The Paris japonica genome weighs in at 152.23 picograms (trillionths of a gram), 15 percent larger than the previously biggest known genome, that of related herb, a hybrid trillium known as Trillium × hagae. “It’s so large that when stretched out it would be taller than Big Ben,” said Ilia Leitch, a research scientist at Kew’s Jodrell Laboratory, in a prepared statement. Human DNA would only stretch out to about two meters. The plant has 150 billion base pairs, compared with humans’ 3 billion.

More than being a monumental discovery, the genome size  shows the vulnerability of this already rare plant. “In plants, research has demonstrated that those with large genomes are at greater risk of extinction, are less adapted to living in polluted soils and are less able to tolerate extreme environmental conditions – all highly relevant in today’s changing world,” Leitch said.

Part of the problem is that large genomes take longer to reproduce, and plants with more DNA require more time to grow. According to a growing guide at Rareplants.co.uk, Paris japonica can take anywhere from two to four years to sprout above ground after planting.

Paris japonica , a canopy plant, is native to Japan, where it lives in sub-alpine regions. According to the Global Biodiversity Information Facility, it has only been observed at seven sites in the wild.

Photo by Ray Drew, courtesy of the Royal Botanic Gardens, Kew.





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  1. 1. jtdwyer 6:32 pm 10/13/2010

    I think there should be little surprise that plant species have much longer genomes than humans, since photosynthesizing cyanobacteria are thought to have been busily accumulating mutations several billion years ago, whereas mammals are new kids on the block.

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  2. 2. E-boy 1:11 pm 10/14/2010

    You do realize that while vertebrate life forms in general and mammals specifically are relatively new individually, we still have a common ancestor with this plant right?

    As of the understanding we have of life at present, every living thing on this planet has a common ancestor with every other living thing on this planet. Which means, they can trace their line of descent just as far back in time and they’ve had just as long to accumulate change. Genomes can shrink over time, as well as get more complex. There are a host of parasitic organisms that can attest to that.

    Link to this
  3. 3. jtdwyer 7:42 pm 10/14/2010

    OK, I’ll accept that that may be the majority view – who actually knows? If life developed or arrived on Earth one time, why could it not have done so two or more times?

    That animals do not extract energy directly from the environment but consume organisms that do may indicate that we could have eliminated a significant amount of DNA required to produce the basic mechanism of external energy extraction.

    The article quotes Ilia Leitch: "In plants, research has demonstrated that those with large genomes are at greater risk of extinction, are less adapted to living in polluted soils and are less able to tolerate extreme environmental conditions – all highly relevant in today’s changing world."

    That statement infers a profound relationship between the amount of genetic instructions accumulated and some sort functional inflexibility. Such a relationship seem counter-intuitive to me and is certainly not explained here.

    My principle point is: what is the significance of having a more lengthy genome and what is the point of comparing the length of any other species’ genome to humans’? There seems to be no meaningful point of comparison.

    Perhaps you can explain…

    Link to this

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