Researchers Shake Out Basis For Rice Domestication

In an article on the cover of the March 31 edition of Science Magazine, MSU scientists, led by Tao Sang, associate professor of plant biology, identify for the first time the genetic mutation for the reduction of shattering, a key step in the domestication of all cereal crops including corn and wheat.

The researchers were able to pinpoint and confirm that a single base pair mutation in DNA causing an amino acid change in a protein led to non-shattering rice varieties. This slight change in DNA prevented mature rice grains from easily falling from stalks to allow a more effective field harvest. In essence, humans several thousand years ago unknowingly practiced de facto gene selection by planting varieties with this trait.

Shattering in cereal crops refers to grains easily falling off of plants. The shattering trait of the wild forerunners of rice and cereals prevents effective field harvest and is undesirable for cultivation.

"What we can learn from historical plant domestication will benefit our ongoing and future effort to domesticate energy crops that will be equally important to the long-term sustainability of our society," Sang said. "It is remarkable how the earliest farmers could have selected a single mutation in DNA to develop a major food crop of the world."

The researchers first determined which chromosomal regions contained the mutations selected for rice domestication. Chromosome 4 was pegged as being responsible primarily for the reduction of shattering.

"Several hundred hours were spent in the greenhouses where we had to shake the plants and record the various degrees of shattering," Sang said. "Even with all the advances in technology, a careful firsthand observation proves to be essential for biological research."

The researchers then developed a new method for rapid and cost-effective DNA isolation to clone a gene from the chromosomal region. Changbao Li, research associate in plant biology, invented a process that increased the speed of DNA isolation and allowed researchers to efficiently complete the screening of 12,000 seedlings.

"This technical innovation will greatly speed up genetic research for plants since it saved us time and money, yet delivered accurate results," Sang said.

"By tracing the breeding of rice and identifying the genetic mutations, the researchers have opened new doors to the science community that benefit the world through a more effective use of the land and water used to grow rice," said Rich Triemer, chairperson of the Department of Plant Biology.

"These findings will improve yields to a crop that is the staple food for more than half of the world's population. Our scientists are continuing the legacy started by William Beal more than one hundred years ago of using plant research to benefit the world," he said.

The article, "Rice Domestication by Reducing Shattering," was published today in Science Express an electronic publication designed to get important papers quickly in front of the scientific community prior to being published in Science. Science is the world's leading journal of original scientific research, global news, and commentary and is published by the American Association for the Advancement of Science.

The research is funded in part by the Michigan Agricultural Experiment Station at MSU.

Other Department of Plant Biology researchers involved in this project include Changbao Li, research associate, and Ailing Zhou, graduate student.