Anchored cyclic peptides for use in crop protection

• Applicant: Dr. Abdulkadir Yayci
• Subject Area: Biological and Biomimetic Chemistry
• Term: from 2022 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 510743119

Cyclotides are naturally occurring, cyclic peptides that inhibit widely occurring agricultural pests such as funghi and insects. In addition to being environmentally benign due to their biological origin, cyclotides have proven broad-range activity and high operational stability, making them a prime candidate to substitute conventional pesticides in agriculture. Current approaches include the production of cyclotides in transgenic crops, making the plants resistant to infestation or infection, or the use of extracts from selected, naturally cyclotide-producing plants that can then be sprayed onto the surface of crops. However, cyclotides also show various interactions with protein targets in humans, which may render transgenic plants unfit for agriculture if the cyclotides are produced heterologously. Plant extracts, on the other hand, are mixtures of a variety of cyclotides, whose composition may change significantly with the growing conditions. If cyclotide-based pesticides are sprayed onto the crops, they can also be easily washed off by rain or irrigation, requiring frequent re-application and thereby increasing cost and environmental impact. The goal of this research project is to combine cyclotides with anchor peptides and to test the efficacy in pest management. Anchor peptides are small peptides that bind tightly to the surface of the crops, making the cargo of the anchor rain-fast. To achieve tight binding, the anchor peptide-cyclotide (APC) is to be produced as a fusion construct. Due to the sophisticated structure of cyclotides, two routes for production are considered: 1) by overexpressing the APC entirely in a biological host or 2) by solid-phase synthesis of the cyclotide, recombinant production of the anchor peptide and the subsequent addition of a cyclizing enzyme (asparaginyl endopeptidase, AEP) that both links the two parts together as well as finalizes the structure of the cyclotide. In both cases, production conditions will be monitored and systematically optimized to ensure that sufficient material for follow-up experiments is produced. The activity of the APC is then tested in a cell model and on various pests to ensure efficacy of the fusion construct. Here, the aim is to generate an APC variant that shows comparable activity to the native cyclotide. In addition, APCs are tested in wash-off experiments on plant parts to ensure long-lasting activity on the surface. Finally, greenhouse experiments are conducted to test whether the APC can protect crops in a rain-fast manner when applied by spraying. Overall, the objective is to gain fundamental knowledge for the design and production principles of peptide-based pesticides and to generate a fully biobased, rain-fast pesticide based on the cyclotide-anchor peptide architecture.

• DFG Programme: WBP Fellowship
• International Connection: Australia
• Host: Professor David Craik