Fusicoccin-A (FC-A) is a fungal phytotoxin best known for forcing stomata open and causing excessive water loss. A 2024 Scientific Reports study showed the opposite effect under carefully controlled conditions: with sufficient water and light, appropriately dosed FC-A increased biomass in Arabidopsis and komatsuna.
FC-A stabilizes the PM H+-ATPase–14-3-3 interaction
FC-A stabilizes binding between plasma-membrane H+-ATPase and 14-3-3 proteins in guard cells, activating the proton pump and promoting stomatal opening. Under drought this can be toxic; when water is sufficient, increased CO₂ entry can support higher photosynthesis.
Daily treatment increased Arabidopsis biomass by about 30%
Ten-day-old Arabidopsis plants received 0.3–30 µM FC-A daily for 15 days. At 30 µM, aboveground fresh and dry weights were about 30% greater than controls. FC-J showed similar growth-promoting activity, whereas the more hydrophilic FC-H did not, supporting a structure-dependent mechanism.
Komatsuna showed a dose window, not unlimited benefit
In hydroponic greenhouse-grown komatsuna, daily FC-A treatment for 28 days increased biomass up to 48 pmol plant−1 day−1. At 480 pmol plant−1 day−1, leaf number and size declined and partial wilting appeared.
FC-A is therefore not simply a toxin or a stimulant: the phenotype depends on dose, water and light.
This is not yet an agricultural biostimulant
The study is a proof of concept in Arabidopsis and komatsuna. Field yield, residues, environmental safety, application cost and regulatory classification remain unresolved. A compound that opens stomata could become harmful under water limitation, so any practical derivative would need a tightly controlled dose and duration.
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Reference
- Kiriyama H et al. Fungal toxin fusicoccin enhances plant growth by upregulating 14-3-3 interaction with plasma membrane H+-ATPase. Scientific Reports. 2024;14:23431. https://doi.org/10.1038/s41598-024-73979-4
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