An international team of scientists has identified and cloned the first gene known to control the production of cellulose--the most abundant organic compound on Earth. Cellulose fibers wrap around cells like barrel hoops, giving plants their basic strength. The discovery, reported in today's issue of Science, could have far-reaching implications for improving wood, paper, cotton, and other plant-based products.
The finding comes from work on a small relative of mustard called Arabidopsis. A team led by Richard Williamson of the Australian National University in Canberra noticed that a mutant Arabidopsis variety produced much less cellulose when grown in soil that was hotter than normal--31 degrees Celsius instead of 18. By breeding the mutant with a normal Arabidopsis plant several times in a row, the Australian group calculated the rough location of the critical gene on one of the plant's five chromosomes. After identifying that short strand of DNA, the team members inserted it into yeast DNA and were able to grow copies of the few dozen genes it contained. Then they used a gene-sequencing machine to decode each one.
Help in identifying the mutant gene came from a team from the University of California, Davis, headed by plant biologist Deborah Delmer. In 1996, her group found strong but not conclusive evidence that an almost identical gene controlled cellulose synthesis in cotton. To prove that the related Arabidopsis gene was the mutant behind cellulose production, Williamson's team isolated a normal gene and cloned it into a mutant plant, which then cranked out normal amounts of cellulose, even at high temperatures.
The cellulose gene may eventually be useful in developing new, high-fiber products, but don't look for tougher clothes or stronger two-by-fours anytime soon. According to Delmer, plants "may have more than 10 genes" regulating cellulose production. That will make genetic engineering of cellulose difficult until all the genes in at least one species are found and understood, she says.