roki3581

Dr. Roy Kirsch

   Department of Entomology
   Molecular Biology of the Insect Digestive System
 Phone:+49 (0)3641 57 1562Max Planck Institute for Chemical Ecology
 Fax:+49 (0)3641 57 1202Hans-Knöll-Straße 8
  emailD-07745 Jena

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Current Reseach:

Evolutionary origin and functional diversification of pectolytic enzymes in herbivorous beetles

Pectin is a highly complex mixture of polysaccharides present in the primary walls 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 contain α-1,4-linked galacturonic acid which makes approximately 70 % of pectin and can be acetylated, methylated or linked to a broad range of sugar molecules. Reflecting this complex structure, microbial plant pathogens and saprophytes secrete a diverse set of pectin degrading enzymes to penetrate plant tissues or directly utilize this huge source of energy. Recently generated transcriptome and genome data show that herbivorous insects also possess genes encoding such enzymes. But whereas these are widely distributed in microbes, pectin degrading enzymes are restricted to a few lineages of herbivorous insects, namely plant bugs and some beetle clades.

I am interested in the evolutionary origin and 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 every plant tissue and organ as well as on decaying plant material. As the composition of cell walls differs between tissues, stages and plant species, the amount and chemistry of pectin the beetles ingest varies. 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. Second, their biological relevance is investigated using the RNAi technique and by tracing the breakdown products released during pectin digestion in the beetle´s gut. 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 second, 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 2014-02-14