title: Glandular β-glucosidases in juvenile Chrysomelina leaf beetles support the evolution of a host-plant-dependent chemical defense.
abstract: Plant-feeding insects are spread across the entire plant kingdom. Because they chew externally on leaves, leaf beetle of the subtribe Chrysomelina sensu stricto are constantly exposed to life-threatening predators and parasitoids. To counter these pressures, the juveniles repel their enemies by displaying glandular secretions that contain defensive compounds. These repellents can be produced either de novo (iridoids) or by using plant-derived precursors. The autonomous production of iridoids pre-dates the evolution of phytochemical-based defense strategies. Both strategies include hydrolysis of the secreted non-toxic glycosides in the defensive exudates. By combining in vitro as well as in vivo experiments, we show that iridoid de novo producing as well as sequestering species rely on secreted β-glucosidases to cleave the pre-toxins. Our phylogenetic analyses support a common origin of chrysomeline β-glucosidases. The kinetic parameters of these β-glucosidases demonstrated substrate selectivity which reflects the adaptation of Chrysomelina sensu stricto to the chemistry of their hosts during the course of evolution. However, the functional studies also showed that the broad substrate selectivity allows building a chemical defense, which is dependent on the host plant, but does not lead to an "evolutionary dead end".
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Rahfeld
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany; Department of Entomology, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Wiebke
authors.initials: W
authors.lastname: Haeger
authors.affiliation: Department of Entomology, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Roy
authors.initials: R
authors.lastname: Kirsch
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Pauls
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Becker
authors.affiliation: Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Halle (Saale), Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Schulze
authors.affiliation: Research Group Mass Spectrometry/Proteomics, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Natalie
authors.initials: N
authors.lastname: Wielsch
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Ding
authors.initials: D
authors.lastname: Wang
authors.affiliation: Genome Analysis Group, Leibniz Institute for Age Research, Fritz Lipmann Institute, Jena, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Groth
authors.affiliation: Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Halle (Saale), Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Brandt
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Boland
authors.affiliation: Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany. Electronic address: aburse@ice.mpg.de.
authors.forename: Antje
authors.initials: A
authors.lastname: Burse
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D044602:Cellulases / Q000096:biosynthesis / Q000378:metabolism*; D001517:Coleoptera / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D039823:Iridoids / Q000378:metabolism; D007814:Larva / Q000201:enzymology / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D018515:Plant Leaves / Q000737:chemistry / Q000469:parasitology; D010944:Plants / Q000737:chemistry / Q000469:parasitology; D034622:RNA Interference
chemical_list: D039823:Iridoids; D044602:Cellulases
keywords: Enzyme kinetics; Evolution; Homology modeling; Insect; RNA interference; β-Glucosidase