Scientists have identified important genes for plant growth whose products help to distribute an vital growth factor throughout the plant. The discovery of these genes means that scientists will be able to design better crops and herbicides. The scientist's findings, reported recently in Science (Vol 282, 2226-2230) and in the December 1998 issue of EMBO Journal (Vol 17, 6903-1911) are regarded as a major breakthrough.
Auxin, an important plant growth factor, plays a key role in determining how and in what direction plants grow. Like many animal hormones, plant growth factors are transported and so have long been regarded to act in a similar fashion to animal hormones. One key difference, though, is that animals have a blood system to transport hormones to target sites around every part of the body, but plants don't. Instead, plants use a specialised delivery system to transport auxin from cell to cell. This delivery system, called the polar auxin transporter, has eluded scientists for a long time, even though its existence had already been postulated in the 1930s. Now, a group headed by Klaus Palme at the Max Delbrck Laboratory in Cologne (a part of the German Max Planck Society) has identified the major parts of this system and provided important pieces in the puzzle of how plant cells communicate with each other.
Plant cells need to communicate with one another to coordinate development of the plant as a whole. For decades, scientists have known that plants move auxin from its site of synthesis in the shoot tips to sites of action elsewhere in the plant. The direction of transport is from the shoot tip down to the tip of the root. Scientists believe it is the movement of auxin that determines the shape of the plant.
The transport of auxin within the plant is a process involving tiny molecular
gates that span the membranes surrounding living plant cells. These gates
selectively allow auxin to flow from one side of the membrane to the other.
Contact: Klaus Palme (MDL), Leo Gäelweiler, Andreas Mueller