Biological and ecological significance of pectin digestion in Phytophaga beetles

• Applicant: Dr. Roy Kirsch
• Subject Area: Animal Physiology and Biochemistry ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: from 2015 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 277315210

The complex polysaccharide structure of the plant cell wall not only maintains cellular integrity but also provides a rich source of energy for organisms that are able to digest it. Plant pathogenic fungi secrete plant cell wall degrading enzymes (PCWDEs) to breach and degrade it. Many plants in turn attempt to counter this attack by producing inhibitors of the fungal enzymes. PCWDEs produced by herbivorous beetles are the subject of increasing attention; but it is not known whether they are inhibited by plant-derived enzyme inhibitors or whether the beetles derive energy from cell wall digestion. This project addresses these questions using a new model system: beetle-produced pectin-degrading polygalacturonases (PGs) and plant-derived PG-inhibiting proteins (PGIPs). PGs from the mustard leaf beetle Phaedon cochleariae will be heterologously expressed and challenged with PGIPs from its host plant to test for binding, PG inhibition and the specificity of PG-PGIP interactions in vitro. Subsequently, PG enzymes will be silenced to in vivo elucidate the biological relevance of pectin degradation and PG inhibition. Catalytically inactive PGs will also be examined to test the hypothesis that they act as decoy molecules, sequestering PGIPs and thus preventing the inhibition of active PGs. Expression patterns of PGIPs in beetle-attacked and fungus-infested plants will be compared to see whether the plants respond differently to these two sources of PGs. These studies will develop a novel aspect of insect-plant interactions at the molecular level, which may provide new ways of controlling beetles which are agricultural pests, as well as more efficient means of biofuel production.

• DFG Programme: Research Grants