Endocytosis and Digestion in Carnivorous Pitcher Plants of the Family Sarraceniaceae

Highly evolved carnivorous plants secrete digestive enzymes for degradation of trapped animals and absorb whole macromolecules from their prey by means of endocytosis. (1) Background: In the pitcher-plant family Sarraceniaceae, the production of enzymes is dubious and no evidence for endocytosis is known so far. (2) Methods: <i>Heliamphora nutans</i>, <i>Darlingtonia californica</i>, and nine taxa of <i>Sarracenia</i> are tested for cuticular pores, and for protease and endocytosis of the fluorescent protein analogue FITC-BSA, after 10&#8722;48 h of stimulation. (3) Results: Cuticular pores as a prerequisite for enzyme secretion and nutrient uptake are present in all tested species. Permeable cells form clusters in the inner epidermis of the pitchers, but are only little differentiated from impermeable epidermis cells. Proteases are found in <i>S. psittacina</i>, <i>S. leucophylla</i>, <i>S. minor</i>, <i>S. oreophila</i>, <i>S. alabamensis</i>, <i>H. nutans</i>, <i>D. californica</i> lacking only in <i>S. flava</i> and in <i>S.</i> <i>purpurea</i> ssp. <i>purpurea</i>, <i>S. purpurea</i> ssp. <i>venosa</i>, <i>S. rosea</i>, where enzyme production is possibly replaced by degradation <i>via</i> the extraordinary diverse inquiline fauna. <i>S.</i> <i>leucophylla</i>, <i>S. minor</i>, <i>S. oreophila</i> exhibit both protease production and endocytosis; <i>S. psittacina</i>, <i>S. alabamensis</i>, <i>H. nutans</i>, <i>D. californica</i> produce proteases only; no single species shows endocytosis without protease production. (4) Conclusions: Protease secretion seems to be a prerequisite for endocytotic nutrient uptake. Transport of FITC-BSA absorbed by endocytosis towards the vascular tissue of the trap leaves suggests that endocytosis of nutrients is more than a side effect of enzyme secretion.

Abstract licence: CC BY

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