title: Carnivorous Nutrition in Pitcher Plants (Nepenthes spp.) via an Unusual Complement of Endogenous Enzymes.
abstract: 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.
authors.affiliation: Department of Biochemistry and Molecular Biology and the Southern Alberta Cancer Research Institute, University of Calgary , Calgary, Alberta T2N 4N1, Canada.
authors.forename: Linda
authors.initials: L
authors.lastname: Lee
authors.affiliation: Department of Biochemistry and Molecular Biology and the Southern Alberta Cancer Research Institute, University of Calgary , Calgary, Alberta T2N 4N1, Canada.
authors.forename: Ye
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Biochemistry and Molecular Biology and the Southern Alberta Cancer Research Institute, University of Calgary , Calgary, Alberta T2N 4N1, Canada.
authors.forename: Brittany
authors.initials: B
authors.lastname: Ozar
authors.affiliation: Institute of Molecular Biotechnology, Graz University of Technology , Graz 8010, Austria.
authors.forename: Christoph W
authors.initials: CW
authors.lastname: Sensen
authors.affiliation: Department of Biochemistry and Molecular Biology and the Southern Alberta Cancer Research Institute, University of Calgary , Calgary, Alberta T2N 4N1, Canada.
authors.forename: David C
authors.initials: DC
authors.lastname: Schriemer
mesh_terms: D000818:Animals; D004063:Digestion; D004798:Enzymes / Q000032:analysis; D005247:Feeding Behavior; D015723:Gene Library; D007313:Insecta / Q000378:metabolism; D013058:Mass Spectrometry; D010940:Plant Proteins / Q000032:analysis / Q000378:metabolism; D020543:Proteome / Q000032:analysis; D052583:Sarraceniaceae / Q000201:enzymology* / Q000378:metabolism
chemical_list: D004798:Enzymes; D010940:Plant Proteins; D020543:Proteome
keywords: Nepenthes; carnivory; enzymes; fluid; mass spectrometry; transcriptomics