Hormone regulates plant growth.

• Position: Vegetation - Auxin

The mechanism by which a key hormone called auxin regulates the growth and development of plants by promoting the degradation of repressor proteins has been discovered by researchers at The University of Texas at Austin. This eventually could allow scientists to manipulate plant growth in desirable ways.

The auxin study was conducted on a plant called Arabidopsis, the first for which the entire genome has been sequenced. Previous research had identified proteins involved in auxin's regulation of many aspects of plant development. This is the first documentation of how the mechanism actually works. It also identifies the specific complex of proteins that promotes degradation of the repressor proteins. Auxin is required for plant growth, stimulating cell division and cell elongation. Among other things, it regulates lateral root formation and the direction in which plants grow, or gravitropism.

Auxin performs its functions by stimulating gene expression--that is, it turns genes on and off. "What we discovered is that the genes involved in these activities are normally off because there are proteins that act as repressors and prevent the genes from being turned on,"...