Open AccessA subset of chemosensory genes differs between two populations of a specialized leaf beetle after host plant shift
Author(s) -
Wang Ding,
Pentzold Stefan,
Kunert Maritta,
Groth Marco,
Brandt Wolfgang,
Pasteels Jacques M.,
Boland Wilhelm,
Burse Antje
Publication year - 2018
Publication title -
ecology and evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.17
H-Index - 63
ISSN - 2045-7758
DOI - 10.1002/ece3.4246
Subject(s) - biology , willow , botany , ionotropic effect , host (biology) , receptor , genetics , nmda receptor
Due to its fundamental role in shaping host selection behavior, we have analyzed the chemosensory repertoire of Chrysomela lapponica . This specialized leaf beetle evolved distinct populations which shifted from the ancestral host plant, willow ( Salix sp., Salicaceae), to birch ( Betula rotundifolia , Betulaceae). We identified 114 chemosensory candidate genes in adult C. lapponica : 41 olfactory receptors ( OR s), eight gustatory receptors, 17 ionotropic receptors, four sensory neuron membrane proteins, 32 odorant binding proteins ( OBP s), and 12 chemosensory proteins ( CSP ) by RNA ‐seq. Differential expression analyses in the antennae revealed significant upregulation of one minus‐C OBP ( Clap OBP 27) and one CSP ( Clap CSP 12) in the willow feeders. In contrast, one OR ( Clap OR 17), four minus‐C OBP s ( Clap OBP 02, 07, 13, 20), and one plus‐C OBP ( Clap OBP 32) were significantly upregulated in birch feeders. The differential expression pattern in the legs was more complex. To narrow down putative ligands acting as cues for host discrimination, the relative abundance and diversity of volatiles of the two host plant species were analyzed. In addition to salicylaldehyde (willow‐specific), both plant species differed mainly in their emission rate of terpenoids such as ( E , E )‐α‐farnesene (high in willow) or 4,8‐dimethylnona‐1,3,7‐triene (high in birch). Qualitatively, the volatiles were similar between willow and birch leaves constituting an “olfactory bridge” for the beetles. Subsequent structural modeling of the three most differentially expressed OBP s and docking studies using 22 host volatiles indicated that ligands bind with varying affinity. We suggest that the evolution of particularly minus‐C OBP s and OR s in C. lapponica facilitated its host plant shift via chemosensation of the phytochemicals from birch as novel host plant.