Plants Starve Caterpillars

red and green tomatoes grow on a vine filling the frame

Biological Strategy

Tomato

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Protect From Animals

Animals–organisms that range from microscopic to larger than a bus–embody a wide variety of harms to living systems, including other animals. They threaten through predation, herbivory, defense, and parasitism, and they compete for resources such as water, nutrients, and space. Any given living organism commonly faces threats from a variety of animals, requiring strategies that effectively defend from each. Trout and other bony fish, for example, escape predators by having scales made of very thin, flake-like pieces of bone covered with slippery mucus. They also have behavioral strategies such as camouflage, fast swimming, and twisting and turning to achieve release from a predator’s grip.

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Catalyze Chemical Breakdown

Life depends upon the building up and breaking down of biological molecules. Catalysts, in the form of proteins or RNA, play an important role by dramatically increasing the rate of a chemical transformation––without being consumed in the reaction. The regulatory role that catalysts play in complex biochemical cascades is one reason so many simultaneous chemical transformations can occur inside living cells in water at ambient conditions. For example, consider the 10-enzyme catalytic breakdown and transformation of glucose to pyruvate in the glycolysis metabolic pathway.

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Flowering Plants

Clade Angiosperms (“receptacle seed”): Dandelions, oaks, grasses, cacti, apples

With 416 families containing some 300,000 known species, angiosperms are the most diverse group of plants, and they can be found around the globe in a wide variety of habitats. They are characterized by seeds that grow enclosed in ovaries, which are enclosed in flowers. The floral organs then develop into fruits of myriad kinds and dimensions, from simple seed casings on maples to elaborate fleshy growths like papayas. The oldest flower known from fossils, Montsechia vidalii, appeared during the Jurassic Period 130 million years ago. They are the primary food source for herbivorous animals, which in turn makes them the indirect food source for carnivores as well.

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Leaves of tomatoes ward off parasitic caterpillars by secreting an enzyme that breaks down a key nutrient in the caterpillar larvae's gut.

While it would be business suicide for any restauranteur to go out of their way to sicken those who eat on its premises, tomato plants depend on such a strategy for their very survival. When the larvae of herbivorous butterflies or moths begin to chew on tomato plant leaves, threonine deaminase, an enzyme commonly found in tomato leaves, changes to a form that enables it to survive the harsh conditions of the lepidopteran gut. In fact, it’s the conditions of the gut that activate this Clark Kent of an enzyme into a superhero molecule that breaks the bonds of threonine, an essential for the lepidopteran larvae’s survival. It may also add nails to the lepidopteran larvae’s coffin by degrading another amino acid, L-serine, and by producing toxic ammonia.

Last Updated September 14, 2016

References

Journal article

Adaptive evolution of threonine deaminase in plant defense against insect herbivores

Proceedings of the National Academy of Sciences | 22/03/2011 | E. Gonzales-Vigil, C. M. Bianchetti, G. N. Phillips, G. A. Howe

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