Dr. Roy Kirsch

   Department of Insect Symbiosis
   Molecular Biology of the Insect Digestive System
 Phone:+49 (0)3641 57 1555Max Planck Institute for Chemical Ecology
 Fax:+49 (0)3641 57 1502Hans-Knöll-Straße 8
  emailD-07745 Jena

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Current Reseach:

Evolutionary origin, functional diversification and ecological relevance of pectolytic enzymes in herbivorous beetles

Pectin is a highly complex mixture of polysaccharides present in the walls and middle lamellae of living plant cells. Its major components, homogalacturonan and rhamnogalacturonans, form a matrix embedding the other plant cell wall polysaccharides, namely cellulose and hemicellulose fibers. Pectic polysaccharides are rich in α-1,4-linked galacturonic acid building blocks, which form the backbone of pectin. Microbial plant pathogens and saprophytes secrete a diverse set of enzymes targeting this backbone to penetrate plant tissues or directly utilize this huge source of energy. A rapidly growing number of transcriptome and genome datasets revealed genes encoding such pectinolytic enzymes also to be present in several herbivorous insect lineages.

I am interested in the evolutionary origin and the biological relevance of pectin degrading enzymes in the two beetle superfamilies Chrysomeloidea (leaf beetles, long-horn beetles) and Curculionoidea (weevils). These closely related lineages are the most successful radiations of herbivorous beetles, feeding on all kinds of plant tissues and organs as well as on decaying plant material. We know from transcriptome data that chrysomeloids possess pectolytic polygalacturonases and curculionoids express in addition carbohydrate esterases and rhamnogalacturonan lyases, all encoded by small gene families. My project is centered first, on the characterization of these pectolytic enzymes after their heterologous expression. Secondly, their biological relevance is investigated using the RNAi-based gene silencing as well as the CRISPR/Cas-based gene knockout method. In addition, the breakdown products released during pectin digestion will be traced in the beetle´s gut to understand how pectin digestion is connected with other metabolic networks. Third, beyond its biological relevance, I am also interested in the ecological impact of pectin digestion, as plants produce pectinase inhibitors potentially contributing to the plant´s defense.
All these approaches will first, help clarifying the benefit for the beetles to express a set of pectolytic enzymes in high amounts in the gut, and secondly, they will also provide insights in the evolution of herbivory and adaptations that reflect sophisticated insect-plant interactions in the chrysomeloid and curculionoid superfamilies.

last updated on 2021-04-14