Carnivorous Nutrition in Pitcher Plants (Nepenthes spp.) via an Unusual Complement of Endogenous Enzymes

J Proteome Res. 2016 Sep 2;15(9):3108-17. doi: 10.1021/acs.jproteome.6b00224. Epub 2016 Aug 1.


Plants belonging to the genus Nepenthes are carnivorous, using specialized pitfall traps called "pitchers" that attract, capture, and digest insects as a primary source of nutrients. We have used RNA sequencing to generate a cDNA library from the Nepenthes pitchers and applied it to mass spectrometry-based identification of the enzymes secreted into the pitcher fluid using a nonspecific digestion strategy superior to trypsin in this application. This first complete catalog of the pitcher fluid subproteome includes enzymes across a variety of functional classes. The most abundant proteins present in the secreted fluid are proteases, nucleases, peroxidases, chitinases, a phosphatase, and a glucanase. Nitrogen recovery involves a particularly rich complement of proteases. In addition to the two expected aspartic proteases, we discovered three novel nepenthensins, two prolyl endopeptidases that we name neprosins, and a putative serine carboxypeptidase. Additional proteins identified are relevant to pathogen-defense and secretion mechanisms. The full complement of acid-stable enzymes discovered in this study suggests that carnivory in the genus Nepenthes can be sustained by plant-based mechanisms alone and does not absolutely require bacterial symbiosis.

Keywords: Nepenthes; carnivory; enzymes; fluid; mass spectrometry; transcriptomics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Digestion
  • Enzymes / analysis
  • Feeding Behavior
  • Gene Library
  • Insecta / metabolism
  • Mass Spectrometry
  • Plant Proteins / analysis
  • Plant Proteins / metabolism
  • Proteome / analysis
  • Sarraceniaceae / enzymology*
  • Sarraceniaceae / metabolism


  • Enzymes
  • Plant Proteins
  • Proteome