Why are some pandas brown? New research solves the mystery

Not everything in life is always black and white. This also applies to giant pandas.

For many years, scientists in China have been fascinated by the Qizai panda, the only brown and white panda in captivity. It was left in the wild and now lives in a Chinese breeding and conservation center. In all, only seven brown and white pandas have been documented – all from Qinling, a mountain range in China's Shaanxi province.

Now a team of researchers has discovered why the 14-year-old male bear has such an unusual coat. Brown pandas lack the short DNA sequence in Bace2, a gene associated with pigmentation. This finding may also apply to brown pandas in the wild.

Brown and white panda

The pandas in Qinling are very different from those in Sichuan, the province where most giant pandas are found.Giant panda melanoleuca) to live. This is what Hu Yibo, one of the researchers, says.

“Previous studies indicate that the Qinling panda separated from the Sichuan panda about 300,000 years ago,” said Hu, a geneticist at the Chinese Academy of Sciences in Beijing.

He and his colleagues studied the genomes of familial triplets — a pair of pandas and their cub — where one of the three pandas was brown and one was white. In addition, they also examined the genomes of 29 other black and white pandas.

The triplets consist of 1) Chizai and his parents, 2) Chizai and his mate and their cub, and 3) Dandan. (The first brown panda was documented about forty years ago)And her mate and their cub. Among them, only Qizai and the now deceased Dandan are brown and white.

Missing information

The researchers hypothesized that brown and white pandas are homozygous for a particular version of Bace2. This means that they have two identical copies of the gene. The research confirmed that both copies of Bace2 in brown and white bears are missing the same 25 base pair in the DNA. “This means that the sequence that codes for that protein has been disrupted, causing the protein to not function properly,” he explains.

DNA analysis of 192 other captive pandas found that none of them had two identical copies of Bace2. Another study also showed that genetically modified mice carrying this mutation have light-colored fur.

The team also found that brown panda fur contains fewer and smaller melanosomes than black pandas. Melanosome is a component of the cell responsible for pigmentation of the coat and skin.

“The core of this research is the discovery that color change can be caused by the absence of a gene or part of it,” says Shi Ping, also an evolutionary geneticist at the Chinese Academy of Sciences.

Scientists now plan to investigate how precisely the discovered mutation leads to changes in the size and number of melanosomes in brown and white pandas.