The mechanism: a mycorrhizal phosphate transporter that also accepts arsenate
Arbuscular mycorrhizal fungi (AMF) are well known to reduce arsenic accumulation in most crops, but they do the opposite in the arsenic hyperaccumulator Pteris vittata. The missing mechanistic link has been a phosphate transporter expressed specifically at the root–AMF interface. Tian et al. now provide in planta evidence that the AMF-inducible P-transporter PvPht1;6 mediates both phosphorus acquisition and arsenate (AsV) uptake in P. vittata.
The team identified two new AMF-enhanced P-transporter genes alongside PvPht1;6 — PvPht1;7 and PvPht1;8 — and confirmed that all three carry typical AMF-responsive promoter elements. Among them, PvPht1;6 showed the strongest AMF induction, rising 15-fold under symbiosis.
What expressing PvPht1;6 in two non-hosts revealed
To test function outside the fern, Tian et al. expressed PvPht1;6 in rice and tobacco under the AMF-inducible promoters OsPT11 and LePT4. In both systems the transgene mirrored native AMF regulation: expression was nearly undetectable without AMF, but under AMF symbiosis it rose 7.2–73 fold in rice and 7.0–26 fold in tobacco.
The effect on phosphorus was consistent across hosts. Shoot P concentrations increased by 16–41% in rice and 11–26% in tobacco, confirming that PvPht1;6 improves P uptake at the root–AMF interface.
Arsenic behaved differently. In rice, PvPht1;6 raised shoot As by 13–38%, but in tobacco it had little effect on shoot As. The discrepancy is explained by a downstream bottleneck: rice possesses efficient OsLsi1/2-mediated As translocation to the shoot, whereas tobacco lacks this pathway. Tobacco still accumulated arsenic — total root As rose 1.1–1.8 fold — but the metal stayed below ground.
Why the host matters for phytoremediation
The result reframes AMF-assisted arsenic phytoextraction. PvPht1;6 can deliver arsenate into the root, yet shoot hyperaccumulation still requires the plant’s own translocation apparatus. This matches what is known about P. vittata: the fern is exceptional not only because it takes up AsV through phosphate transporters, but because it efficiently moves arsenic from root to frond and converts it to less toxic arsenite for storage.
For field practice, the implication is that simply inoculating a site with AMF will not guarantee more arsenic in harvestable biomass. The outcome depends on whether the host plant has the downstream transporters and detoxification machinery to move arsenic above ground. P. vittata does; most non-hyperaccumulators do not.
Opportunities and risks
The clearest opportunity is dual-use remediation: boosting both phosphorus nutrition and arsenic removal on marginal or contaminated land. In arsenic-affected regions where soil P is also limiting, an AMF–PvPht1;6 combination could make P. vittata deployments more robust, especially where native AMF colonisation is patchy.
The risk is over-generalisation. The rice and tobacco data show that PvPht1;6-driven As uptake can be decoupled from shoot accumulation. Engineering or inoculating other species with this transporter may increase root As loading without producing a harvestable shoot product — potentially slowing rather than accelerating cleanup if roots senesce and release arsenic back into soil.
Caveats
The article is a gold open-access pre-proof published online on 20 August 2026; the final version-of-record is scheduled for the October 2026 issue of Soil & Environmental Health. I verified the load-bearing numbers from the publisher abstract and metadata via three independent source checks, but I could not retrieve the full PDF programmatically because the ScienceDirect site returns a bot challenge. Claims are therefore bounded to what the authors report in the abstract and to the mechanism inferred from the heterologous expression experiments.
Provenance: primary source verified through the publisher DOI, Crossref, OpenAlex and independent three-vendor fact-check; see /methodology/ for the hyperaccumulate.com editorial process.