Date: Mon, 15 Jun 1998 10:31:31 From: SCHLAUER@chemie.uni-wuerzburg.de To: cp@opus.hpl.hp.com Message-Id: <aabcdefg2031$foo@default> Subject: _Sarracenia purpurea_ enzymes
Gallie, D.R. & Chang, S.C.
"Signal transduction in the carnivorous plant _Sarracenia
purpurea_. Regulation of secretory hydrolase expression during
development and in response to resources."
Plant Physiology 115 (4): 1461-1471 (1997)
Abstract:
"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."
The hydrolase activities have been tested enzymatically. Bacterial
contamination has been demonstrated not to play any role within the
first two weeks after pitcher opening. This excellent paper puts a
definitive end to all fairy tales and rumours that _S. purpurea_ was
"dependent" on bacterial digestion because of an alleged absence of
endogenous hydrolytic enzymes. Therefore, the whole genus
_Sarracenia_, and (as demonstrated by previous work by Jaffe,
Michelangeli, Gonzalez, Miras & Ruiz, New Phytol. 122:733-744, 1992)
parts of _Heliamphora_ are carnivorous beyond doubt. Another
important result reconfirming that Sarraceniaceae are (essentially) a
carnivorous plant family.
Kind regards
Jan
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