White Tiger's Coat Produced by Change in One Gene

All it took was one single change in a known pigment gene for the white tiger to get its striking color, according to new research from a Chinese laboratory.

White tigers are rare breeds of the typical orange species of Bengal tiger (Panthera tigris tigris). Records of white tigers go back the 1500s on the Indian subcontinent, though the last known free-roaming white tiger was shot in 1958. Today the only remaining white tigers exist in captive programs at animal conservations centers and zoos.

The BBC reports the limited number of white tigers still living are interbred to maintain their distinctive fur color, which has been viewed as a recessive trait. The inbreeding results sometimes in eyesight problems and deformities.

Prior to the new research, the genetic basis of tiger whiteness was unknown.

"The white tiger represents part of the natural genetic diversity of the tiger that is worth conserving, but is now seen only in captivity," said Shu-Jin Luo of China's Peking University.

Luo's team mapped the genomes of 16 tigers living in Chimelong Safari Park, including both white and orange individuals. They then sequenced the whole genomes of each of the three parents in the family.

The genomic mapping led to them to zero in on SLC45A2, a pigment gene which has long been associated with the light coloration seen in some human populations and in a range of other animals including horses, chickens, and fish. The white tigers carried a variant of the gene that inhibited production of red and yellow pigments, but did not affect black pigments, which explains why white tigers still show characteristic black stripes.

The researchers wrote that the because so many adult white tigers were killed by hunters throughout history, the unnaturally white cats must have been fit to thrive in the jungles. It's also noteworthy that the tiger's main prey, deer, are likely colorblind, the researchers said.

Luo said that now that the gene that makes tigers white has been identified, it will allow them to explore the evolutionary forces that have maintained tigers of both orange and white varieties.

The research was published in the journal Current Biology.