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The Rigakubu News
The Rigakubu News, Sep. 2025.
Research Student Communicates to Faculty >
Visualizing the Effects of Antiplatelet Drugs
Keisuke Goda (Professor, Department of Chemistry)
ISome organisms have flourished by acquiring abilities that most others lack, thereby opening up new ecological niches. Understanding the mechanisms by which such novel abilities arise has long been a central concern in evolutionary biology, and strange flowers that emit odors reminiscent of rotten meat to deceive flies into pollinating them provide an excellent example. Recently, we succeeded in uncovering how multiple plant lineages independently acquired the ability to produce such foul odors, showing that this specialized form of evolution can, contrary to expectation, occur through relatively simple steps.
Our research focuses on how diverse angiosperms, which form the foundation of terrestrial ecosystems, have evolved in association with various pollinators, including insects. Members of the genus Asarum (family Aristolochiaceae) exhibit strikingly different floral scents from species to species, attracting different groups of flies, which are then exploited as pollinators without offering nectar or other rewards. A key component of this floral scent diversity is dimethyl disulfide (DMDS), a compound that constitutes the main odor of rotting meat and carnivore feces. Since some closely related Asarum species emit DMDS while others do not, we hypothesized that comparative analysis could reveal the mechanism—previously unknown—by which flowers produce DMDS.
By narrowing down candidate genes whose expression levels correlated with differences in DMDS emission among Asarum species, we identified two genes, MGL and SBP. Biochemical assays showed that the enzymes encoded by these genes use methionine, a sulfur-containing amino acid, as a substrate, and that DMDS is synthesized through the combined action of the two enzymes. In particular, the second reaction, catalyzed by the SBP-derived enzyme, represented a previously unknown step crucial to the ability to produce the “foul odor.” We therefore named this enzyme disulfide synthase (DSS).
Although DSS was expected to be a newly evolved enzyme specific to Asarum, further investigation revealed the surprising presence of functionally equivalent enzymes in distantly related plants, including Eurya japonica and Symplocarpus renifolius. Detailed analysis showed that in Asarum, Eurya, and Symplocarpus, DSS originated from a gene duplication of the universally conserved SBP gene in angiosperms, followed by the same amino acid changes that altered enzymatic function. Remarkably, this process had occurred independently in each lineage. This represents a striking case of molecular convergent evolution, in which distinct evolutionary lineages acquire the same traits under common selective pressures. Thus, foul-smelling flowers offer us a remarkable glimpse into the mechanisms of biological evolution. These findings were published in Y. Okuyama et al., Science, 388, 656 (2025).
Conceptual diagram of this research