Putative Sugar Transporters of the Mustard Leaf Beetle Phaedon cochleariae: Their Phylogeny and Role for Nutrient Supply in Larval Defensive Glands

Phytophagous insects can tolerate and detoxify toxic compounds present in their host plants and have evolved intricate adaptations to this end. Some insects even sequester the toxins for their defence. This necessitates specific mechanisms, especially carrier proteins that regulate uptake and transport to specific storage sites or protect sensitive tissues from noxious compounds. We identified three ATP-binding cassette subfamily B (ABCB) transporters from the transcriptome of the cardenolide-sequestering leaf beetle Chrysochus auratus and analysed their functional role in the sequestration process. These were heterologously expressed and tested for their ability to interact with various potential substrates: verapamil (standard ABCB substrate), the cardenolides digoxin (commonly used), cymarin (present in the species's host plant) and calotropin (present in the ancestral host plants). Verapamil stimulated all three ABCBs and each was activated by at least one cardenolide, however, they differed as to which they were activated by. While the expression of the most versatile transporter fits with a protective role in the blood–brain barrier, the one specific for cymarin shows an extreme abundance in the elytra, coinciding with the location of the defensive glands. Our data thus suggest a key role of ABCBs in the transport network needed for cardenolide sequestration.

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Iridoid Monoterpene Biosynthesis in Insects: Evidence for a De Novo Pathway Occurring in the Defensive Glands of Phaedon armoraciae (Chrysomelidae) Leaf Beetle Larvae

The Science of Nature ◽

10.1007/s001140050318 ◽

1996 ◽

Vol 83 (10) ◽

pp. 470-473 ◽

Cited By ~ 3

Author(s):

N. J. Oldham ◽

M. Veith ◽

W. Boland ◽

Konrad Dettner

Keyword(s):

De Novo ◽

Leaf Beetle ◽

Defensive Glands ◽

Monoterpene Biosynthesis

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Precise RNAi-mediated silencing of metabolically active proteins in the defence secretions of juvenile leaf beetles

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2012.1342 ◽

2012 ◽

Vol 279 (1745) ◽

pp. 4126-4134 ◽

Cited By ~ 19

Author(s):

René Roberto Bodemann ◽

Peter Rahfeld ◽

Magdalena Stock ◽

Maritta Kunert ◽

Natalie Wielsch ◽

...

Keyword(s):

Alcohol Oxidase ◽

Leaf Beetle ◽

Leaf Beetles ◽

Juvenile Hormone Binding Protein ◽

Defensive Glands ◽

Hormone Binding Protein ◽

Chemical Stimuli ◽

Poplar Leaf ◽

Novel Protein

Allomones are widely used by insects to impede predation. Frequently these chemical stimuli are released from specialized glands. The larvae of Chrysomelina leaf beetles produce allomones in gland reservoirs into which the required precursors and also the enzymes are secreted from attached gland cells. Hence, the reservoirs can be considered as closed bio-reactors for producing defensive secretions. We used RNA interference (RNAi) to analyse in vivo functions of proteins in biosynthetic pathways occurring in insect secretions. After a salicyl alcohol oxidase was silenced in juveniles of the poplar leaf beetles, Chrysomela populi , the precursor salicyl alcohol increased to 98 per cent, while salicyl aldehyde was reduced to 2 per cent within 5 days. By analogy, we have silenced a novel protein annotated as a member of the juvenile hormone-binding protein superfamily in the juvenile defensive glands of the related mustard leaf beetle, Phaedon cochleariae . The protein is associated with the cyclization of 8-oxogeranial to iridoids (methylcyclopentanoid monoterpenes) in the larval exudates made clear by the accumulation of the acylic precursor 5 days after RNAi triggering. A similar cyclization reaction produces the secologanin part of indole alkaloids in plants.

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The mustard leaf beetle, Phaedon cochleariae, as a screening model for exogenous RNAi-based control of coleopteran pests

Pesticide Biochemistry and Physiology ◽

10.1016/j.pestbp.2021.104870 ◽

2021 ◽

pp. 104870

Author(s):

Sonja Mehlhorn ◽

Julia Ulrich ◽

Christian U. Baden ◽

Benjamin Buer ◽

Frank Maiwald ◽

...

Keyword(s):

Leaf Beetle ◽

Screening Model ◽

Phaedon Cochleariae

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ABC transporter functions as a pacemaker for sequestration of plant glucosides in leaf beetles

eLife ◽

10.7554/elife.01096 ◽

2013 ◽

Vol 2 ◽

Cited By ~ 38

Author(s):

Anja S Strauss ◽

Sven Peters ◽

Wilhelm Boland ◽

Antje Burse

Keyword(s):

Leaf Beetle ◽

Leaf Beetles ◽

Host Plant Specialization ◽

Defensive Strategies ◽

Atp Binding Cassette Transporter ◽

Defensive Glands ◽

Herbivore Interactions ◽

Plant Herbivore ◽

Multiple Chemical

Plant-herbivore interactions dominate the planet’s terrestrial ecology. When it comes to host–plant specialization, insects are among the most versatile evolutionary innovators, able to disarm multiple chemical plant defenses. Sequestration is a widespread strategy to detoxify noxious metabolites, frequently for the insect’s own benefit against predation. In this study, we describe the broad-spectrum ATP-binding cassette transporter CpMRP of the poplar leaf beetle, Chrysomela populi as the first candidate involved in the sequestration of phytochemicals in insects. CpMRP acts in the defensive glands of the larvae as a pacemaker for the irreversible shuttling of pre-selected metabolites from the hemolymph into defensive secretions. Silencing CpMRP in vivo creates a defenseless phenotype, indicating its role in the secretion process is crucial. In the defensive glands of related leaf beetle species, we identified sequences similar to CpMRP and assume therefore that exocrine gland-based defensive strategies, evolved by these insects to repel their enemies, rely on ABC transporters as a key element.

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