Understanding natural crop defenses( LA JOLLA CA Ever since insects deve...)

LA JOLLA, CA Ever since insects developed a taste for vegetation, plants have faced the same dilemma: use limited resources to out-compete their neighbors for light to grow, or, invest directly in defense against hungry insects. Now, an international team of scientists at the Salk Institute for Biological Studies and the Institute of Investigaciones Fisiolgicas y Ecolgicas Vinculadas a la Agronoma (IFEVA) has discovered how plants weigh the tradeoffs and redirect their energies accordingly.

The same light sensor that detects other plants crowding in and gives the signal to switch on the synthesis of the plant growth hormone auxin reduces the plant's responsiveness to the hormone jasmonic acid, which orchestrates the synthesis of a whole array of defensive chemicals, the researchers report in an article published in the current early online edition of the Proceedings of the National Academy of Sciences.

"Understanding how plants resolve the dilemma of resource allocation on a mechanistic level opens the possibility to increase the natural defenses of crops, especially in the high density plantings typical of modern agriculture, which depend on regular applications of insecticides," explains senior author Carlos L. Ballar, Ph.D., a senior scientist with CONICET (the National Research Council of Argentina) and associate professor at the University of Buenos Aires.

In an earlier study, Ballar discovered that plants dial down their investment in defense when they perceive an increased risk of competition for light. But just how changes in light quality caused plants to drop their guards were still poorly understood. To connect the two, he turned to Howard Hughes Medical Institute investigator Joanne Chory, Ph.D., in the Plant Biology Laboratory at the Salk Institute and former lab member, Yi Tao, Ph.D., who had dissected the molecular pathway that plants use to adjust their growth and flowering time to shade.

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