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Scientists have isolated the world's oldest DNA traces from pandas from a fossil dating back 22,000 years and discovered a new lineage of the species.
The report, published in the journal Current Biology, shows that the ancient panda found in Cizhutuo Cave in Guangxi Province in China separated from the current pandas 144,000 to 227,000 years ago, suggesting that he belonged to a separate group.
"Using a single complete mitochondrial DNA sequence (mt), we find a distinct mitochondrial lineage, suggesting that the Cizhutuo panda, although genetically closer to the pandas today than at present. Other bears, has a deep and separate history of the common ancestor of current pandas, "said Qiaomei Fu of the Chinese Academy of Sciences.
"This really highlights that we have to sequence more DNA from the old pandas to really grasp how their genetic diversity has changed over time and how that relates to their current, much smaller and fragmented habitat," Fu said. .
Very little is known about the pandas' past, particularly in areas outside their current range in Shaanxi Province or in Gansu and Sichuan Provinces.
Evidence suggests that pandas in the past were much more prevalent, but it is unclear how these pandas were related to pandas today.
In the new study, researchers used sophisticated methods to fish mitochondrial DNA from the ancient specimen of the cave. This is a particular challenge because the specimen comes from a subtropical environment, which makes it difficult to preserve and recover DNA.
The researchers successfully sequenced nearly 150,000 DNA fragments and aligned them to the mitochondrial genome reference sequence of the giant panda to recover the complete mitochondrial genome of the Cizhutuo panda. They then used the new genome with the mitochondrial genomes of 138 current bears and 32 old bears to build a family tree.
Their badysis shows that the split between the Cizhutuo panda and the ancestor of the current pandas dates back to around 183,000 years ago. The Cizhutuo panda also has 18 mutations that would alter the structure of proteins through six mitochondrial genes.
The researchers said that these amino acid changes can be related to the distinct habitat of the ancient panda in Guangxi or perhaps climatic differences during the last glacial maximum. The findings suggest that the maternal lineage of the ancient panda had a long and unique history that differed from maternal lineages leading to current pandas populations.
The researchers said their success in capturing the mitochondrial genome also suggests that they could isolate and successfully badyze the much more expansive nuclear genome DNA from the old specimen.
"The comparison of Cizhutuo panda nuclear DNA with current data on the entire genome would allow a deeper badysis of the evolutionary history of the Cizhutuo specimen, as well as its common history with the current pandas," he said. said Fu.
Very little is known about the pandas' past, particularly in areas outside their current range in Shaanxi Province or in Gansu and Sichuan Provinces.
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