In Plants, "Calling All Cells" Means Busy Electrical Circuits

By Don Comis
June 14, 1999

BELTSVILLE, Md., June 14--Drought, an insect walking on a plant leaf, a friendly pat from a gardener: All can trigger the equivalent of a cellular "911 call" from a plant to literally all of its cells, warning them to prepare for defense, according to a scientist at USDA's Agricultural Research Service.

The existence of such warning systems has been known for a long time, but no one knows how they work. Now, ARS plant molecular biologist Frank J. Turano reports the "cell phone network" may run along neural "lines" similar to those found in animals.

"Plant cells respond to changes in their environment and warn distant parts of the plant of potential problems," said Turano.

His preliminary studies at the ARS Climate Stress Laboratory in Beltsville, Md., are starting to unravel the molecular workings behind this cellular communication system. The research may lead to new tactics for strengthening crop plants' capacities to adapt, survive and thrive in different environmental conditions.

Turano has identified and cloned a dozen genes that enable plants to make receptors similar to those found in animal nerves. Previously, only two plant genes of this type have been reported in the scientific literature.

He believes that these receptors may be responsible for an electrical signaling system in plants. "Knowing where the receptor genes are the most active could help pin down the basic mechanism for cell-to-cell signaling that may be involved in plant growth and environmental responses," he said.

Turano has also cloned plant genes that control glutamate and GABA--gamma- aminobutyric acid--levels in plants. Glutamate and GABA are two amino acids known to control neural signal transmission in animals. Turano speculates that plants beset by insects or other stresses may use glutamate or GABA to trigger a chain reaction by opening the receptor's "floodgate." A flood of ions passing through this gate may initiate an electrical signal. The signal may trigger a long distance cell-to-cell message that can warn and prepare the plant to defend itself.

The signaling system will be explored under a cooperative research and development agreement between ARS and Auxein Corp. of Lansing, Mich. Turano will pursue the genetic and molecular studies, while Auxein scientists will concentrate on the physiological aspects of the system. ARS and Auxein are applying for patent protection on the genes and technology.

Scientific contact: Frank J. Turano, ARS Climate Stress Laboratory, Beltsville, Md., phone (301) 504-5527, fax (301) 504-6626, fturano@asrr.arsusda.gov.