Insecticidal diversity of butterfly pea (Clitoria ternatea) accessions

Abstract Butterfly pea (Clitoria ternatea) is currently the only leguminous plant species known to produce a suite of ultrastable cyclic plant defense peptides called cyclotides. For agricultural applications, cyclotides have attracted significant interest, leading to the recent registration of a butterfly pea extract as an ecofriendly pesticide (Sero-X®). In this study, we set out to distinguish the variation in cyclotide expression and toxicity towards insect cells for butterfly pea accessions sourced worldwide. In characterizing the peptide extracts from 23 butterfly pea accessions sourced from 11 countries, we show that significant variation in cyclotide expression exists between them. For some accessions, the cyclotide Cter M, typically the most abundantly expressed cyclotide in vegetative butterfly pea tissues, is absent. Genomic and transcriptomic sequencing revealed the presence of CterM-like precursor genes in these accessions that contained missense mutations that were likely contributing to the lack of Cter M expression. Peptide profiling also showed that one accession does not produce detectable levels of other cyclotides: cliotide T1, cliotide T4, Cter A and Cter Q. A comparison of cytotoxicity against Sf9 (Spodoptera frugiperda) cells revealed that cytotoxicity is not dependent on Cter M, with accessions lacking this peptide also displaying cytotoxicity. Overall, insights from this study provides foundational knowledge about characters to be considered for selective breeding of butterfly pea with enhanced insecticidal properties.