PLANT PHYSIOLOGY , Vol 115, Issue 4 1461-1471, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Signal Transduction in the Carnivorous Plant Sarracenia purpurea (Regulation of Secretory Hydrolase Expression during Development and in Response to Resources)
D. R. Gallie and S. C. Chang
Department of Biochemistry, University of California, Riverside, California 92521-0129
Carnivory in plants has developed as an evolutionary adaptation to
nutrient-poor environments. A significant investment of the resources of a
carnivorous plant is committed to producing the traps, attractants, and
digestive enzymes needed for the carnivory. The cost:benefit ratio of
carnivory can be improved by either maximizing the prey capture rate or by
reducing the metabolic commitment toward carnivory. Using the pitcher plant
Sarracenia purpurea, we have investigated whether the expression of the
hydrolytic enzymes needed for digestion is regulated in response to the
presence of prey. Expression of protease, RNase, nuclease, and phosphatase
activities could be induced in the fluid of nonactive traps by the addition
of nucleic acids, protein, or reduced nitrogen, suggesting that hydrolase
expression is induced upon perception of the appropriate chemical signal.
Hydrolase expression was also developmentally controlled since expression
commenced upon opening of a trap, increased for several days, and in the
absence of prey largely ceased within 2 weeks. Nevertheless, the traps
remained competent to induce expression in response to the appropriate
signals. These data suggest that in young traps hydrolase expression is
developmentally regulated, which is later replaced by a signal transduction
mechanism, and they demonstrate the ability of a carnivorous species to
respond to the availability of resources.
