Research Article: Metabolite profiling of the carnivorous pitcher plants Darlingtonia and Sarracenia

Date Published: February 21, 2017

Publisher: Public Library of Science

Author(s): Hannu Hotti, Peddinti Gopalacharyulu, Tuulikki Seppänen-Laakso, Heiko Rischer, Vijai Gupta.

http://doi.org/10.1371/journal.pone.0171078

Abstract

Sarraceniaceae is a New World carnivorous plant family comprising three genera: Darlingtonia, Heliamphora, and Sarracenia. The plants occur in nutrient-poor environments and have developed insectivorous capability in order to supplement their nutrient uptake. Sarracenia flava contains the alkaloid coniine, otherwise only found in Conium maculatum, in which its biosynthesis has been studied, and several Aloe species. Its ecological role and biosynthetic origin in S. flava is speculative. The aim of the current research was to investigate the occurrence of coniine in Sarracenia and Darlingtonia and to identify common constituents of both genera, unique compounds for individual variants and floral scent chemicals. In this comprehensive metabolic profiling study, we looked for compound patterns that are associated with the taxonomy of Sarracenia species. In total, 57 different Sarracenia and D. californica accessions were used for metabolite content screening by gas chromatography-mass spectrometry. The resulting high-dimensional data were studied using a data mining approach. The two genera are characterized by a large number of metabolites and huge chemical diversity between different species. By applying feature selection for clustering and by integrating new biochemical data with existing phylogenetic data, we were able to demonstrate that the chemical composition of the species can be explained by their known classification. Although transcriptome analysis did not reveal a candidate gene for coniine biosynthesis, the use of a sensitive selected ion monitoring method enabled the detection of coniine in eight Sarracenia species, showing that it is more widespread in this genus than previously believed.

Partial Text

Sarraceniaceae is a New World carnivorous plant family comprising three genera: Darlingtonia Torr. (monotypic), Heliamphora Benth. (ca. 23 species [1]) and Sarracenia L. (ca. 11 species [2]). The distribution of Darlingtonia is limited to a few locations along the western coast of North America, Heliamphora occurs mainly on tepuis of the Guiana Highlands in South America and Sarracenia is the most widespread genus in the family, found in the eastern coastal plains of North America. Darlingtonia californica, Sarracenia, and Heliamphora are able to compete in nutrient-poor habitats due to their insectivorous nature, i.e. the ability to attract, capture, and digest insects to supplement their nutrient uptake. A common feature for all three genera is that they lure insects to their elongated tubular leaves. In order to attract insects, they produce extrafloral nectar [3], emit insect attractants [4], and most species are brightly colored. They utilize various methods to capture their prey. Darlingtonia californica and S. psittacina, for example, hide their entry/exit hole from the inside, displaying multiple translucent false exits so that insects finally get exhausted and fall into the pitcher. Other Sarracenia and Heliamphora species utilize downward pointing hairs and waxy surfaces in their pitchers in order to trap insects.

Studied accessions of Sarraceniaceae possessed a diverse variety of compounds. Lids and pitchers were studied separately and approximately 600 compounds were detected in both collections. The accessions also showed huge diversity, with every accession containing unique compounds. Coniine was newly detected in seven Sarracenia species in addition to the known source, S. flava. However, we could not identify a specific candidate gene involved in coniine biosynthesis in Sarracenia spp. Among the common constituents of Sarraceniaceae are sarracenin, erucamide, and nonanal. By integrating existing phylogenetic information of Sarraceniaceae, we successfully demonstrated that the phylogeny can explain the metabolite composition of the plants. Phylogeny explained the presence or absence of compounds more strongly than their concentrations.

 

Source:

http://doi.org/10.1371/journal.pone.0171078