Millipede genes reveal how plants and animals evolved similar defense chemicals

Jim Crocker
26th November, 2025

Millipede genes reveal how plants and animals evolved similar defense chemicals

Cyanogenesis process in Chamberlinius hualienensis millipedes and the broader cyanohydrin biosynthesis pathway shared by millipedes, insects, and plants, highlighting the key enzymes involved in converting amino acids to defensive compounds like hydrogen cyanide.

Image adapted from: Yamaguchi, Asano. / CC BY (Source)

Key Findings

  • This study sequenced the genome of a millipede, Chamberlinius hualienensis, revealing insights into how it defends itself with hydrogen cyanide (HCN)
  • Millipedes evolved the ability to produce HCN independently from plants and insects, utilizing a unique set of enzymes for this defense mechanism
  • Researchers identified a novel enzyme, ChuaMOxS, responsible for the first step in HCN production in this millipede, differing from the pathways found in plants and insects
Hydrogen cyanide (HCN) is a potent chemical compound used as a defense mechanism by a surprising variety of organisms, from plants to insects and even millipedes. Unlike many defensive chemicals unique to specific groups of organisms, the ability to produce HCN, termed “cyanogenesis”, appears to have evolved independently multiple times across the tree of life. This widespread, yet sporadic, occurrence has long puzzled scientists[2]. A key question has been understanding how different organisms developed this capability, and whether they utilize similar biochemical pathways. Recent research from Toyama Prefectural University and Universidad de Valparaiso[1] has shed light on the cyanogenesis process in millipedes, specifically Chamberlinius hualienensis. For 140 years, it has been known that millipedes can release HCN as a defense, but the specific enzymes involved remained unknown. This study aimed to identify and characterize the complete set of enzymes responsible for HCN production in this millipede species. The researchers employed a combination of techniques. First, they sequenced the genome of C. hualienensis – essentially, they determined the complete genetic code of the millipede. Then, they used biological characterization, meaning they tested the function of specific genes identified in the genome to confirm their role in cyanogenesis. This involved identifying the enzymes involved and demonstrating their activity in the laboratory. The study revealed a fascinating picture of how cyanogenesis evolved in millipedes. A crucial enzyme, hydroxynitrile lyase, which releases HCN from a precursor molecule called (R)-mandelonitrile, was found to have multiple, closely related copies of its gene. This suggests the gene duplicated over time, with each copy potentially evolving slightly different functions. Interestingly, the initial step in producing (R)-mandelonitrile differs from that seen in most plants and insects. Plants and insects typically use an enzyme called cytochrome P450 (CYP) to convert a compound called aldoxime into cyanohydrin, a precursor to (R)-mandelonitrile. However, the millipede utilizes a different enzyme, a flavin-dependent monooxygenase (ChuaMOxS), more similar to that found in ferns[3]. This finding supports the idea that cyanogenesis has arisen through multiple, independent evolutionary pathways. Furthermore, the conversion of aldoxime to nitrile – another step in the process – also differs in millipedes. While a single CYP enzyme handles this conversion in plants and insects, the millipede requires two CYP enzymes (CYP4GL4 and CYP30008A2) to accomplish the same task, followed by a third CYP (CYP3201B1) to form the final (R)-mandelonitrile product. This research builds upon earlier observations that plants and insects sometimes produce identical secondary metabolites, despite their evolutionary distance[2]. These shared compounds could arise from parallel functions, or even from independent evolution of the same chemical structures. The study of benzoxazinoids (BXDs) provides a compelling example of this independent evolution, with BXD biosynthesis arising multiple times in the plant kingdom, utilizing different enzymes each time[3]. Similarly, the polyacetylenic fatty acid 8Z-dihydromatricaria acid is found in plants, fungi and soldier beetles, with the soldier beetle having evolved its own unique pathway for production[4]. The findings from demonstrate that millipedes evolved their cyanogenic defenses independently from both plants and insects. This is further evidence of the metabolic plasticity observed in nature, where organisms can arrive at similar chemical solutions using entirely different enzymatic machinery. The repeated evolution of cyanogenesis, and the diverse enzymatic pathways involved, highlights the power of natural selection to converge on effective defense mechanisms, even through different routes. The study also illustrates how repeated evolution can occur, where new enzymes with the same function evolve independently from a shared pool of related enzymes[5].

GeneticsAnimal ScienceEvolution

References

Main Study

1) Cyanogenic millipede genome illuminates convergent evolution of cyanogenesis-related enzymes

Published 24th November, 2025

https://doi.org/10.1371/journal.pgen.1011955

Related Studies

2) Chemical convergence between plants and insects: biosynthetic origins and functions of common secondary metabolites.

https://doi.org/10.1111/nph.15718

3) Reinventing metabolic pathways: Independent evolution of benzoxazinoids in flowering plants.

https://doi.org/10.1073/pnas.2307981120

4) The convergent evolution of defensive polyacetylenic fatty acid biosynthesis genes in soldier beetles.

https://doi.org/10.1038/ncomms2147

5) Genetics and biochemistry of secondary metabolites in plants: an evolutionary perspective.

Journal: Trends in plant science, Issue: Vol 5, Issue 10, Oct 2000


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