As concerns grow over the threat of bioterrorism and weapons of mass destruction, Penn State University genetic researchers are working on an early warning system -- the figurative canary in the mineshaft -- that could be as unobtrusive and ubiquitous as plants in a landscape. This canary is a specially engineered plant or group of plants designed to detect and signal the presence of many harmful chemical or biological agents.

In theory, soldiers could be equipped with a hand-held electronic device. When pointed at a native plant, the readings on the device would indicate the plant was exposed to nerve gas some time in the last several hours or several days. At present such a device does not exist.

To develop such technology, the Defense Advanced Research Projects Agency has awarded Penn State University a 3 year, $3.5 million grant to lay groundwork for genetically engineered plants that can detect the presence of harmful nerve agents. Plants are a suitable candidate because they are rooted to their environment, and cannot move out of a given area like an insect or other animal. They can therefore become a short-term history book of their environment over the last several days. Just as a plant will wilt without water, or become lighter green with less nitrogen, a plant that is genetically altered to become sensitive to a nerve agent or other chemical compounds poisonous to humans would retain certain effects of its exposure.

Plants and animals detect and respond to a range of things -- including microbes, insects, chemicals and hormones -- via cellular proteins. These proteins, called receptor-like kinases (RLKs), have a sensing domain outside the cell membrane that binds molecules in the environment. This binding sends a signal inside the cell to the response domain, known as the kinase, which then turns on genes that trigger a response. One of the plants being studied at Penn State is Arabidopsis, a small flowering plant from the mustard family that grows around the world and is widely used as a model organism in plant biology.

Even detection of something such as explosives in the soil is under research. A military commander, with the proper electronic device, could receive a readout from a plant in his locale that could indicate the presence of explosives nearby. Of course, such genetically modified plants would have to be planted into the environment ahead of time, which may pose its own set of problems.

Jack Schultz, a chemical ecologist and professor of entomology in the College of Agricultural Sciences, indicates in the Penn State extension website that their experiments may eventually aid the agricultural community as well. One example given was that a sensor could be mounted on the front of a farm tractor traveling across a field when operating a pesticide sprayer. The sensor could detect the presence of a certain weed or insect pest and turn the sprayer on or off or add different chemical components for a given section of the field, and thus reduce the total volume of pesticides used.