Media type: E-Article Title: Anthraquinones as defensive compounds in eggs of Galerucini leaf beetles: Biosynthesis by the beetles? Contributor: Pankewitz, Florian; Zöllmer, Anja; Gräser, Yvonne; Hilker, Monika imprint: Wiley, 2007 Published in: Archives of Insect Biochemistry and Physiology Language: English DOI: 10.1002/arch.20215 ISSN: 0739-4462; 1520-6327 Keywords: Insect Science ; General Medicine ; Biochemistry ; Physiology Origination: Footnote: Description: <jats:title>Abstract</jats:title><jats:p>Eggs of leaf beetles of the tribe Galerucini, subfamily Galerucinae, contain polyketides that are unusual in insects: 1,8‐dihydroxylated anthraquinones (chrysazin, chrysophanol) and anthrones (dithranol, chrysarobin) deterring predators. The host plants do not contain these compounds. In the present study, we tested the hypothesis that the beetles, but not bacterial or fungal microorganisms living as endosymbionts within the beetles, produce the anthraquinones. The tansy leaf beetle <jats:italic>Galeruca tanaceti</jats:italic> was used as Galerucini model organism. It was treated with antimicrobial substances to eradicate the microorganisms and inhibit the hypothesised endosymbiotic anthraquinone production. Despite treatment, female <jats:italic>G. tanaceti</jats:italic> laid eggs containing anthraquinones. Although broad spectrum antimicrobials were used, it cannot be excluded that the potential endosymbiotic microorganisms are resistant. Given that the hypothesised endosymbionts are transferred via the eggs from one generation to the next, bacterial or fungal DNA was expected to be present in the eggs. With the exception of <jats:italic>Wolbachia pipientis</jats:italic>, however, no further 16S rDNA from bacteria responsible for anthraquinone biosynthesis was detected in eggs of untreated beetles. Because <jats:italic>Wolbachia</jats:italic> were also found in closely related anthraquinone‐free insects, we exclude these bacteria as producers of the defensive polyketides. Nor was any 18S rDNA from fungi with anthraquinone biosynthetic abilities detected. Our results indicate that anthraquinones and anthrones in eggs of Galerucini are produced by beetle enzymes and not by endosymbiotic microorganisms within the eggs. Arch. Insect Biochem. Physiol. 66:98–108, 2007. © 2007 Wiley‐Liss, Inc.</jats:p>