( able to get that to work in a test tube...)At long last, scientists figure out how plants grow

Auxin may stick around awhile, but it is eventually broken down by natural cell processes.

The scientists used the common plant model Arabidopsis thaliana (wall cress) for their experiments. They also expressed TIR1 in insect cell cultures, to make sure that the binding of TIR1 to auxin is not directly influenced by other plant cell proteins.

Auxins influence a wide variety of plant processes. For example, they are the hormones that cause roots to grow downward and flowers to track the moving sun. Auxins also stop the growth of lateral branches. Since auxins are produced in shoot tips, lopping off the tip can cause numerous side shoots to appear, giving a plant a denser, more sculpted look.

Auxin also promotes fruit development. In strawberries, for example, auxin produced by the developing seeds promotes the growth of a red and juicy fruit.

Another protein called ABP1 (Auxin Binding Protein 1) has previously been shown to bind auxin. But unlike TIR1 and auxin, it remains unclear whether the pairing of ABP1 and auxin actually stimulates plant growth.

The research reported by Estelle, Dharmasiri and Dharmasiri was funded by grants from the National Science Foundation, the National Institutes of Health and the U.S. Department of Energy.

To speak with Estelle, please call 812-856-1216 or e-mail him at maestell@indiana.edu.

"The F-box protein TIR1 is an auxin receptor," Nature, v. 435, no. 7040