Scientists discover protein switch that controls how plants absorb nitrogen fertilizer

Researchers at New York University have identified a protein that acts as a molecular stop signal for nitrogen uptake in plants, a discovery that could eventually give breeders a genetic target for developing crops that use fertilizer far more efficiently. The study, published in The Plant Cell, centers on a transcription factor called HHO5.

How HHO5 works as a nitrogen brake

The NYU team found that HHO5 tells a plant when it has absorbed enough nitrogen and can stop taking more from the soil. When nitrogen levels in the plant reach a threshold, HHO5 expression rises and triggers a cascade of downstream gene changes that effectively shut down the uptake machinery. The protein responds specifically to organic nitrogen, the form plants use for long-distance transport, storage and synthesis of amino acids essential to human nutrition.

“By identifying gene regulators that are sensitive to different levels and types of nitrogen, we uncovered a regulatory factor controlling nitrogen use and a key to improving nitrogen uptake and assimilation into organic nitrogen in plants,” said Gloria Coruzzi, the Carroll and Milton Petrie Professor in NYU’s Department of Biology and Center for Genomics and Systems Biology and co-senior author of the study.

Why plant nitrogen efficiency matters for fertilizer

Crops globally use only about 30–50% of the nitrogen fertilizer applied to fields. The rest escapes into waterways as nitrate runoff or enters the atmosphere as nitrous oxide, a greenhouse gas roughly 300 times more potent than carbon dioxide per unit. Improving nitrogen use efficiency at the plant level is one of the most direct paths to reducing both fertilizer costs and environmental damage.

Current approaches to improving nitrogen use efficiency focus primarily on the soil side: slow-release coatings, nitrification inhibitors and precision application timing. The HHO5 discovery opens a complementary path by targeting the plant’s own regulatory wiring. If breeders can modify how aggressively HHO5 shuts down nitrogen uptake, crops could potentially pull more nitrogen from the soil before the brake engages, reducing the amount of unused fertilizer left behind.

From lab discovery to field application

The research team found that different forms of nitrogen had distinct effects on HHO5 expression levels. Inorganic nitrogen, the form directly absorbed from fertilizer, triggered a different response pattern than organic nitrogen. This distinction matters because it suggests the signaling pathway is nuanced enough that breeders could potentially fine-tune it without disrupting other metabolic processes.

NYU has filed a patent application covering the research and its potential use in improving plant nitrogen use efficiency. The university did not disclose licensing discussions, but the patent signals commercial intent.

The discovery arrives at a moment when nitrogen fertilizer costs are elevated globally. U.S. retail urea prices averaged $594 per tonne in early August, according to USDA data, and have declined only modestly from mid-year peaks driven by the Strait of Hormuz disruption. Any genetic improvement that lets crops extract more value from each tonne of applied nitrogen would directly affect farm economics.

A growing field of nitrogen efficiency research

The NYU work fits into a broader wave of nitrogen efficiency research. A Purdue study published in July identified a genetic switch controlling nitrogen fixation in soybeans, while Washington State University researchers reported in May that nitrogen-fixing genes could be transferred between bacterial strains. Companies including Pivot Bio, Intrinsyx Bio and Kula Bio are commercializing microbial approaches to biological nitrogen fixation.

What distinguishes the HHO5 finding is its focus on the plant’s own signaling rather than the soil microbiome. It targets a regulatory checkpoint that exists in all plants, not just legumes, which means any improvement could theoretically apply across major cereal crops including corn, wheat and rice.

Still, translating a transcription factor discovery into a commercial crop variety typically takes a decade or more. The immediate value lies in giving plant scientists a specific, well-characterized genetic target to work with as they pursue varieties that deliver more grain per unit of applied nitrogen.

Source: Phys.org