Fort Collins, Colorado
February 21, 2003

Plants that lose their color, when sensing chemical signals is what biologists from the Colorado State University are developing for multiple future uses.

Dr. Reddy and Dr. June Medford, both professors of biology at Colorado State University, have teamed up to investigate the possibility of producing plants that would lose their green color, when they come into contact with specific chemical signals.

The main element in plants that is responsible for their green color is chlorophyll. As seasons change, plants can regulate the production of chlorophyll. In the fall, many plants will stop producing chlorophyll in preparation for the loss of leaves.

As a model plant for their investigation, Professors Medford and Reddy will use Arabidopsis, or Thale cress, because the genome of Arabidopsis has already been entirely sequenced. Thus, using the Arabidopsis will allow the professors to have access to a wealth of genetic information, which will decrease the time it takes to finish the project.

In Arabidopsis, there are two main genes that are responsible for the break down of chlorophyll, which in turn cause the plant to lose its green color. The research groups of Dr. Medford and Reddy will seek to overproduce these enzymes in Arabidopsis plants, with the hopes of speeding up the time it takes the plant to degrade chlorophyll.

In addition, the groups will introduce a gene that will have an end effect of blocking the production of new chlorophyll. Commenting on the goal of using this three gene approach Dr. Reddy said, “In this way we hope that the plant loses its color in hours – instead of days like in the natural process.”

The third part of the project involves the triggering mechanism for the system. The plan is to couple the three decolorizing genes to receptors that can sense either a plant or animal hormone and act as the systems trigger. After all these components are introduced into Arabidopsis, Dr. Reddy noted, “When we spray the plant (Arabidopsis) with a plant hormone or estrogen, it will hopefully loose its green color.”

The team has set the goal of developing the plant defense cascade in Arabadopsis within the next 18 months. For this period, the researchers have recently received a grant of nearly 500,000 dollars from Defense Advanced Research Projects Agency.

To make use of the plants sentinels in our daily life, the researchers also plan to create new receptor triggering systems that will recognize hazardous chemicals such as, toxins, gases and environmental pollutants. Commenting on some future options Dr. Reddy said, “The Toll-like receptor, a receptor that recognizes flagellar protein from Salmonella, is similar to the one for brassinosteroids, like estrogen.” He wants to take the outer part of the Toll-like receptor, and fuse it to parts of receptors involved in triggering the plant defence cascade, so that the system can recognize the flagellar protein from Salmonella.

Dr. Reddy also believes receptors recognizing other biological and chemical hazards could be used as soon as they have established a working model in Adabidopsis. Besides being aesthetically pleasing, these early warning plants offer an inexpensive alternative to existing devices. Such plants could be kept in offices, mass-transit stations and shopping centers, for example, to help alert individuals of a bioterrorist attack.

Other possibilities with this innovative technology include using algae and plants to monitor water pollution — be it through bioterrorist means or through hazardous wastes from industries and cities. Dr. Reddy also noted that outdoor evergreen plants, with similar artificial circuits, could be monitored by satellite as early detection systems and as environmental sentinels.

Although the project has a time frame of 18 months, Dr Reddy cautions that, “An inexpensive warning system may be 10 to 15 years off. Right now, we are doing the proof-of-principle studies.”