Just so stories (botanical division): How the pitcher plant digests bugs

The carnivorous plants, which in the wild "... live mostly in the Asian tropics... rely on occasional insect snacks to stay nourished, since they mostly grow in nutritient-depleted soil," wrote Rick Weiss in an item in the February 4, 2008 Washington Post.

Above, an interesting video detailing the overall process.

Scientists in Japan have now learned precisely how they digest their prey and they reported their findings in a paper in the January 28, 2008 issue of the Journal of Proteome Research; the abstract follows.

Proteome Analysis of Pitcher Fluid of the Carnivorous Plant Nepenthes alata

The genus Nepenthes comprises carnivorous plants that digest insects in pitcher fluid to supplement their nitrogen uptake. In a recent study, two acid proteinases (nepenthesins I and II) were purified from the pitcher fluid. However, no other enzymes involved in prey digestion have been identified, although several enzyme activities have been reported. To identify all the proteins involved, we performed a proteomic analysis of Nepenthes pitcher fluid. The secreted proteins in pitcher fluid were separated by sodium dodecyl sulfate−polyacrylamide gel electrophoresis, and several protein bands [below]



were detected by silver staining. The proteins were identified by in-gel tryptic digestion, de novo peptide sequencing, and homology searches against public databases. The proteins included homologues of β-D-xylosidase, β-1,3-glucanase, chitinase, and thaumatin-like protein, most of which are designated “pathogenesis-related proteins”. These proteins presumably inhibit bacterial growth in the pitcher fluid to ensure sufficient nutrients for Nepenthes growth.