Isolation and Characterization of Insecticidal Cyclotides from Viola communis

Area of Science:

• Biochemistry
• Molecular Biology
• Proteomics

Background:

• Cyclotides are cysteine-rich peptides with cyclic backbones and disulfide bonds.
• They possess beneficial biophysical properties for pharmaceutical and agricultural use.
• The Violaceae family is a major source of cyclotides, with Viola communis previously showing inferred presence.

Purpose of the Study:

• To investigate the occurrence, sequences, and properties of cyclotides in Viola communis.
• To identify and characterize novel cyclotides from this plant.
• To explore the potential insecticidal activity of identified cyclotides.

Main Methods:

• Proteomics and transcriptomics were employed to identify cyclotides.
• Mass spectrometry was used for peptide identification.
• Biological assays were conducted to determine cytotoxicity and potency.

Main Results:

• Twenty cyclotides were identified in Viola communis, including two new members: Vcom1 (bracelet subfamily) and Vcom2 (Möbius subfamily).
• Vcom1 and Vcom2 exhibited cytotoxicity against Sf9 insect cells, with Vcom1 being more potent.
• Seven new cyclotide-like sequences were found in the transcriptome, suggesting Violaceae as a rich source for novel cyclotides.

Conclusions:

• Viola communis contains a diverse range of cyclotides with potential insecticidal applications.
• Bracelet cyclotides demonstrate higher insecticidal activity than Möbius cyclotides.
• New insights into cyclotide processing and biosynthesis were gained, suggesting alternative N-terminal processing enzymes.