Sequestration of phytochemicals by leaf beetles: Selective transport proteins and their influence on diversification processes in plant-herbivore interactions

点击翻译按钮获取中文摘要

Insects can have the capability to use plant derived secondary metabolites for their own defense against predators. The leaf beetle larvae of the subtribe Chrysomelina developed specialized defensive glands in which such plant metabolites are converted, stored and released in case of attack. Detailed studies of the sequestration process revealed a functional network of transport processes guiding plant derived glucosides through the larval body. The initial uptake by the larvae’s intestine seems to be fairly unspecific, which contrasts sharply with the specific import of precursors into the defensive glands. Excretion organs facilitate the rapid clearing of body fluid from excess or unusable compounds. The sequestration of glucosides represents a mechanism widely spread in the insect world. Due to their water solubility these compounds can pass membranes only under controlled conditions. Transport proteins modified their substrate specificity to translocate such glucosylated phytochemicals. With this function they are in a key position during the adaptation process of herbivores to their host plants. Despite their obvious importance such transport proteins haven’t neither identified nor characterized up to now. Because of the carrier network identified in the Chrysomelina species so far, this subtribe represents an excellent model system to study sequestration. The detailed understanding of membrane transfer allows on one hand to draw parallels to other sequestering insects and on the other hand to discover factors that interfere with co-evolution of insects and plants.