Polyketides in insects: ecological role of these widespread chemicals and evolutionary aspects of their biogenesis

Abstract

Polyketides are known to be used by insects for pheromone communication and defence against enemies. Although in microorganisms (fungi, bacteria) and plants polyketide biogenesis is known to be catalysed by polyketide synthases (PKS), no insect PKS involved in biosynthesis of pheromones or defensive compounds have yet been found. Polyketides detected in insects may also be biosynthesized by endosymbionts. From a chemical perspective, polyketide biogenesis involves the formation of a polyketide chain using carboxylic acids as precursors. Fatty acid biosynthesis also requires carboxylic acids as precursors, but utilizes fatty acid synthases (FAS) to catalyse this process. In the present review, studies of the biosynthesis of insect polyketides applying labelled carboxylic acids as precursors are outlined to exemplify chemical approaches used to elucidate insect polyketide formation. However, since compounds biosynthesised by FAS may use the same precursors, it still remains unclear whether the structures that are formed from e.g. acetate chains (acetogenins) or propanoate chains (propanogenins) are PKS or FAS products. A critical comparison of PKS and FAS architectures and activities supports the hypothesis of a common evolutionary origin of these enzyme complexes and highlights why PKS can catalyse the biosynthesis of much more complex products than can FAS. Finally, we summarise knowledge which might assist researchers in designing approaches for the detection of insect PKS genes.

Harvestman Phenols and Benzoquinones: Characterisation and Biosynthetic Pathway

“…The biosynthesis of 1-hepten-3-one produced by the harvestman Iporangaia pustulosa (Gonyleptidae) was recently described [24] as the condensation of one acetate and two propionate units following a polyketide pathway. However, there is no evidence of polyketide synthases (PKS) in harvestmen or in any other arthropod species studied so far [25]. These results claimed that additional evidence of PKS activities lay in the production of other classes of harvestman metabolites, such as benzoquinones.…”

RNA Sequencing, De novo assembly, functional annotation and SSR analysis of the endangered diving beetle Cybister chinensis (= Cybister japonicus) using the Illumina platform

“…The metabolism of the terpenoids polyketides contained a lesser number of sequences under the secondary metabolites category. These pathways may be required to establish the ecological dependence, interactions, and evolutionary relationships (Pankewitz and Hilker ). Two sequences classified to ubiquinone and other terpenoid‐quinone biosynthesis pathway consistent to the detection of methylhydroquinone, and toluquinone 2, 3‐dimethylquinone in the larval transcriptome of the carabid beetle, Chlaenius cordicollis (Holliday et al .…”

First Biosynthetic pathway of 1-hepten-3-one in Iporangaia pustulosa (Opiliones)

“…13). On the basis of the PKS mode of action14 we propose assembling to initiate with a propionyl-CoA (C 3 ), which is extended by a malonyl-CoA (C 2 ) and a methylmalonyl-CoA (C 3 ) (Fig.…”