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

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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Role of de novo biosynthesis in ecosystem scale monoterpene emissions from a boreal Scots pine forest

Biogeosciences ◽

10.5194/bg-8-2247-2011 ◽

2011 ◽

Vol 8 (8) ◽

pp. 2247-2255 ◽

Cited By ~ 28

Author(s):

R. Taipale ◽

M. K. Kajos ◽

J. Patokoski ◽

P. Rantala ◽

T. M. Ruuskanen ◽

...

Keyword(s):

Scots Pine ◽

De Novo ◽

Proton Transfer Reaction ◽

Eddy Covariance Method ◽

De Novo Biosynthesis ◽

Monoterpene Biosynthesis ◽

Monthly Changes ◽

Scots Pine Forest ◽

Storage Pools

Abstract. Monoterpene emissions from Scots pine have traditionally been assumed to originate as evaporation from specialized storage pools. More recently, the significance of de novo emissions, originating directly from monoterpene biosynthesis, has been recognized. To study the role of biosynthesis at the ecosystem scale, we measured monoterpene emissions from a Scots pine dominated forest in southern Finland using the disjunct eddy covariance method combined with proton transfer reaction mass spectrometry. The interpretation of the measurements was based on a correlation analysis and a hybrid emission algorithm describing both de novo and pool emissions. During the measurement period May–August 2007, the monthly medians of daytime emissions were 200, 290, 180, and 200 μg m−2 h−1. The emissions were partly light dependent, probably due to de novo biosynthesis. The emission potential for both de novo and pool emissions exhibited a decreasing summertime trend. The ratio of the de novo emission potential to the total emission potential varied between 30 % and 46 %. Although the monthly changes were not significant, the ratio always differed statistically from zero, suggesting that the role of de novo biosynthesis was observable. Given the uncertainties in this study, we conclude that more accurate estimates of the contribution of de novo emissions are required for improving monoterpene emission algorithms for Scots pine dominated forests.

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Implication of HMGR in homeostasis of sequestered and de novo produced precursors of the iridoid biosynthesis in leaf beetle larvae

Insect Biochemistry and Molecular Biology ◽

10.1016/j.ibmb.2007.09.006 ◽

2008 ◽

Vol 38 (1) ◽

pp. 76-88 ◽

Cited By ~ 15

Author(s):

Antje Burse ◽

Sindy Frick ◽

Axel Schmidt ◽

Rita Buechler ◽

Maritta Kunert ◽

...

Keyword(s):

De Novo ◽

Leaf Beetle

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Deciphering the route to cyclic monoterpenes in Chrysomelina leaf beetles: source of new biocatalysts for industrial application?

Zeitschrift für Naturforschung C ◽

10.1515/znc-2017-0015 ◽

2017 ◽

Vol 72 (9-10) ◽

pp. 417-427 ◽

Cited By ~ 2

Author(s):

Antje Burse ◽

Wilhelm Boland

Keyword(s):

De Novo ◽

Sustainable Use ◽

Building Blocks ◽

Leaf Beetle ◽

Industrial Applications ◽

Metabolic Diversity ◽

Leaf Beetles ◽

Wide Range ◽

Extreme Habitats ◽

Plant Sources

AbstractThe drastic growth of the population on our planet requires the efficient and sustainable use of our natural resources. Enzymes are indispensable tools for a wide range of industries producing food, pharmaceuticals, pesticides, or biofuels. Because insects constitute one of the most species-rich classes of organisms colonizing almost every ecological niche on earth, they have developed extraordinary metabolic abilities to survive in various and sometimes extreme habitats. Despite this metabolic diversity, insect enzymes have only recently generated interest in industrial applications because only a few metabolic pathways have been sufficiently characterized. Here, we address the biosynthetic route to iridoids (cyclic monoterpenes), a group of secondary metabolites used by some members of the leaf beetle subtribe Chrysomelina as defensive compounds against their enemies. The ability to produce iridoids de novo has also convergently evolved in plants. From plant sources, numerous pharmacologically relevant structures have already been described. In addition, in plants, iridoids serve as building blocks for monoterpenoid indole alkaloids with broad therapeutic applications. As the commercial synthesis of iridoid-based drugs often relies on a semisynthetic approach involving biocatalysts, the discovery of enzymes from the insect iridoid route can account for a valuable resource and economic alternative to the previously used enzymes from the metabolism of plants. Hence, this review illustrates the recent discoveries made on the steps of the iridoid pathway in Chrysomelina leaf beetles. The findings are also placed in the context of the studied counterparts in plants and are further discussed regarding their use in technological approaches.

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De novo biosynthesis versus sequestration: A network of transport systems supports in iridoid producing leaf beetle larvae both modes of defense

Insect Biochemistry and Molecular Biology ◽

10.1016/j.ibmb.2008.06.005 ◽

2008 ◽

Vol 38 (10) ◽

pp. 895-904 ◽

Cited By ~ 36

Author(s):

Maritta Kunert ◽

Astrid Søe ◽

Stefan Bartram ◽

Sabrina Discher ◽

Karla Tolzin-Banasch ◽

...

Keyword(s):

De Novo ◽

Leaf Beetle ◽

Transport Systems ◽

De Novo Biosynthesis

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Molecular Characterization of Donacia provosti (Coleoptera: Chrysomelidae) Larval Transcriptome by De Novo Assembly to Discover Genes Associated with Underwater Environmental Adaptations

Insects ◽

10.3390/insects12040281 ◽

2021 ◽

Vol 12 (4) ◽

pp. 281

Author(s):

Haixia Zhan ◽

Youssef Dewer ◽

Cheng Qu ◽

Shiyong Yang ◽

Chen Luo ◽

...

Keyword(s):

Molecular Mechanisms ◽

De Novo ◽

Orthologous Gene ◽

Leaf Beetle ◽

Scientific Basis ◽

Protein Coding ◽

Effective Prevention ◽

Gene Pairs ◽

Major Pest ◽

And Control

Donacia provosti (Fairmaire, 1885) is a major pest of aquatic crops. It has been widely distributed in the world causing extensive damage to lotus and rice plants. Changes in gene regulation may play an important role in adaptive evolution, particularly during adaptation to feeding and living habits. However, little is known about the evolution and molecular mechanisms underlying the adaptation of D. provosti to its lifestyle and living habits. To address this question, we generated the first larval transcriptome of D. provosti. A total of 20,692 unigenes were annotated from the seven public databases and around 18,536 protein-coding genes have been predicted from the analysis of D. provosti transcriptome. About 5036 orthologous cutlers were identified among four species and 494 unique clusters were identified from D. provosti larvae including the visual perception. Furthermore, to reveal the molecular difference between D. provosti and the Colorado potato beetle Leptinotarsa decemlineata, a comparison between CDS of the two beetles was conducted and 6627 orthologous gene pairs were identified. Based on the ratio of nonsynonymous and synonymous substitutions, 93 orthologous gene pairs were found evolving under positive selection. Interestingly, our results also show that there are 4 orthologous gene pairs of the 93 gene pairs were associated with the “mTOR signaling pathway”, which are predicted to be involved in the molecular mechanism of D. provosti adaptation to the underwater environment. This study will provide us with an important scientific basis for building effective prevention and control system of the aquatic leaf beetle Donacia provosti.

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Role of de novo biosynthesis in ecosystem scale monoterpene emissions from a boreal Scots pine forest

Biogeosciences Discussions ◽

10.5194/bgd-7-8019-2010 ◽

2010 ◽

Vol 7 (6) ◽

pp. 8019-8040 ◽

Cited By ~ 2

Author(s):

R. Taipale ◽

M. K. Kajos ◽

J. Patokoski ◽

P. Rantala ◽

T. M. Ruuskanen ◽

...

Keyword(s):

Scots Pine ◽

De Novo ◽

Hybrid Approach ◽

Proton Transfer Reaction ◽

Eddy Covariance Method ◽

De Novo Biosynthesis ◽

Monoterpene Biosynthesis ◽

Emission Modelling ◽

Scots Pine Forest

Abstract. Monoterpene emissions from Scots pine have traditionally been assumed to originate as evaporation from specialized storage pools. More recently, the significance of de novo emissions, originating directly from monoterpene biosynthesis, has been recognized. To study the role of biosynthesis in the ecosystem scale, we measured monoterpene emissions from a Scots pine dominated forest in southern Finland using the disjunct eddy covariance method combined with proton transfer reaction mass spectrometry. The interpretation of the measurements was based on a hybrid emission algorithm describing both de novo and pool emissions. During the measurement period May–August 2007, the monthly medians of daytime emissions were 170, 280, 180, and 180 μg m−2 h−1. The emission potential for both de novo and pool emissions exhibited a decreasing summertime trend. The ratio of the de novo emission potential to the total emission potential varied between 30% and 46%. Although the monthly changes were not significant, the ratio always differed statistically from zero, i.e., the role of de novo biosynthesis was evident. The hybrid approach showed promising potential for the improvement of the ecosystem scale emission modelling. Given this feature and the significant role of biosynthesis, we recommend incorporating both de novo and pool emissions into the monoterpene emission algorithms for Scots pine dominated forests.

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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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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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