Max Planck Institute for Chemical Ecology, Beutenberg Campus, Hans-Knoell-Str. 8, 07745 Jena, Germany.
Proc Biol Sci. 2012 Oct 22;279(1745):4126-34. doi: 10.1098/rspb.2012.1342. Epub 2012 Aug 8.
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.
信息素被昆虫广泛用于阻止捕食。这些化学刺激物通常从专门的腺体中释放出来。叶甲科幼虫在腺体储器中产生信息素，所需的前体和附着在腺体细胞上的酶也被分泌到储器中。因此，储器可以被认为是产生防御性分泌物的封闭生物反应器。我们使用 RNA 干扰 (RNAi) 来分析昆虫分泌物生物合成途径中蛋白质的体内功能。在白杨叶甲幼虫中沉默水杨酸醇氧化酶后，水杨酸醇在 5 天内增加到 98%，而水杨酸醛减少到 2%。类似地，我们在相关的芥菜叶甲幼虫的幼虫防御腺中沉默了一种被注释为保幼激素结合蛋白超家族成员的新型蛋白。该蛋白与环化 8-氧香叶醛成裂环烯醚萜（甲基环戊烷单萜）有关，这在 RNAi 触发 5 天后，非环化前体的积累表明了幼虫分泌物中的这种关系。类似的环化反应产生植物中吲哚生物碱的 secologanin 部分。
