Scientists say rare plant has biggest genome yet

Thu Oct 7, 2010 11:15am EDT
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By Kate Kelland

LONDON (Reuters) - When it comes to genomes, size matters -- and British scientists say a rare and striking plant native to Japan is in a perilous position.

Researchers at Britain's Kew Botanical Gardens say the plant, Paris japonica, has the largest genome yet recorded, putting it at high risk of extinction.

"Some people may wonder what the consequences are of such a large genome and whether it really matters if one organism has more DNA than another," said Ilia Leitch, a researcher at Kew's Jodrell Laboratory. "The answer to this is a resounding 'yes'"

"Having a large genome increases the risk of extinction. The larger it is, the more at risk you are."

The vast range of genome size -- the amount of DNA -- in plants and animals has long fascinated and puzzled scientists.

With 152.23 picograms (pg) of DNA, the Paris japonica has around 15 percent more than the previous record holder, the marbled lungfish or Protopterus aethiopicus, with 132.83 pg.

It is also more than 50 times bigger than the human genome, which is 3.0 picograms. A picogram is one trillionth of a gram.

Leitch said the importance of size lies in the fact that the more DNA there is in a genome, the longer it takes for a cell to copy all of its DNA and divide.   Continued...

<p>A Paris japonica is seen in a handout photo. REUTERS/Karl Kristensen</p>