A photograph shows a shell of an "Akoya" pearl oyster and pearls harvested in Japan at the University of Tokyo. (Mainichi)

A team of Japanese scientists has identified almost all of about 30,000 different kinds of genes that form the shell of pearl oysters, a discovery that could shed light on the mystery surrounding the beauty of pearls.

A team of scientists from the University of Tokyo, the Pearl Research Institute of Mikimoto Co., Ltd., and other organizations found 29,682 unique sequences containing novel gene candidates for nacreous and prismatic layer formation, using a device called a "GS FLX 454 system." Some of the genes had already been known, but most of them had not been identified.

The production of the "Akoya" pearl oyster, or pinctada, a genus of pearl oysters, has been decreasing in recent years, but the finding could help select superior species to harvest pearls in high genetic qualities.

On June 23, the research finding was posted on the electronic edition of "PLoS ONE," a publication dedicated to presenting the results of scientific research from any scientific discipline in an open-access environment.

Pearl oysters are raised in many parts of the world, but the pinctada, or the "Akoya" pearl oyster, is said to be particularly beautiful. A pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The protein trapped between pearl layers is composed of various genes that are believed to control the growth and sparkling of a pearl.

Of about 30,000 kinds of genes identified, 52 of which are involved in the formation of pearl layers, about two thirds of them had been unknown. "We want to uncover the reason why Japan's 'Akoya' pearl oyster can form elaborate pearl layers to produce beautiful sparkles," said Shugo Watanabe, professor at the University of Tokyo.