Phyllotreta striolata flea beetles use host plant defense compounds to create their own glucosinolate-myrosinase system.

Abstract

The ability of a specialized herbivore to overcome the chemical defense of a particular plant taxon not only makes it accessible as a food source but may also provide metabolites to be exploited for communication or chemical defense. Phyllotreta flea beetles are adapted to crucifer plants (Brassicales) that are defended by the glucosinolate-myrosinase system, the so-called "mustard-oil bomb." Tissue damage caused by insect feeding brings glucosinolates into contact with the plant enzyme myrosinase, which hydrolyzes them to form toxic compounds, such as isothiocyanates. However, we previously observed that Phyllotreta striolata beetles themselves produce volatile glucosinolate hydrolysis products. Here, we show that P. striolata adults selectively accumulate glucosinolates from their food plants to up to 1.75% of their body weight and express their own myrosinase. By combining proteomics and transcriptomics, a gene responsible for myrosinase activity in P. striolata was identified. The major substrates of the heterologously expressed myrosinase were aliphatic glucosinolates, which were hydrolyzed with at least fourfold higher efficiency than aromatic and indolic glucosinolates, and β-O-glucosides. The identified beetle myrosinase belongs to the glycoside hydrolase family 1 and has up to 76% sequence similarity to other β-glucosidases. Phylogenetic analyses suggest species-specific diversification of this gene family in insects and an independent evolution of the beetle myrosinase from other insect β-glucosidases.

• Authors: Franziska Beran, Yannick Pauchet, Grit Kunert, Michael Reichelt, Natalie Wielsch, Heiko Vogel, Andreas Reinecke, Aleš Svatoš, Inga Mewis, Daniela Schmid, Srinivasan Ramasamy, Christian Ulrichs, Bill S Hansson, Jonathan Gershenzon, David G Heckel
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 111 Issue 20 Pg. 7349-54 (May 20 2014) ISSN: 1091-6490 [Electronic] United States
• PMID: 24799680 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Glucosinolates
• Plant Proteins
• Cellulases
• Glycoside Hydrolases
• thioglucosidase

Topics

• Animals
• Arabidopsis (chemistry)
• Cellulases (metabolism)
• Coleoptera (enzymology, immunology, physiology)
• Expressed Sequence Tags
• Female
• Gene Expression Regulation, Enzymologic
• Glucosinolates (chemistry)
• Glycoside Hydrolases (metabolism)
• Herbivory
• Hydrogen-Ion Concentration
• Hydrolysis
• Male
• Molecular Sequence Data
• Phylogeny
• Plant Proteins (metabolism)
• Substrate Specificity