Plants are surrounded by billions of soil bacteria, but only a few actively help them grow. Now, researchers have pinpointed exactly how one such beneficial bacterium communicates with its host—and the molecule it uses turns out to be a powerful growth booster not just for citrus, but for peppers, celery, and mustard as well. The discovery opens a new avenue for developing stable, microbe-derived alternatives to traditional fertilizers.
For decades, scientists have known that certain plant growth-promoting rhizobacteria (PGPR) enhance crop performance through various mechanisms—producing hormones, solubilizing nutrients, or suppressing pathogens. Yet the specific chemical signals that mediate these beneficial interactions, particularly in woody perennial crops like citrus, have remained largely elusive. Based on these challenges, there is a clear need for in-depth research into the molecular dialogue between citrus and its rhizosphere microbiome.
Now, a team led by researchers at Huazhong Agricultural University in China, in collaboration with the University of Maryland, has identified a key player in this dialogue. Publishing (DOI: 10.1093/hr/uhag071) on February 28, 2026, in Horticulture Research , the scientists show that a dominant citrus rhizobacterium, Burkholderia strain Burk_2H3, promotes plant growth by secreting N-(3-oxo-octanoyl)-L-homoserine lactone—a molecule they named PGPHL—which significantly enhances nutrient uptake across multiple crop species.
The research team began by isolating Burk_2H3 from citrus rhizosphere soils across 15 distinct growing sites. Metabolomic profiling revealed that PGPHL was 9.7 to 17.2 times more abundant in the secretions of this growth-promoting strain than in three non-promoting Burkholderia strains. When applied exogenously, PGPHL increased citrus seedling dry weight by 43.12%. Transcriptomic analysis showed that Burk_2H3, its cell-free supernatant, and PGPHL all consistently upregulated key nutrient transporter genes in citrus roots—including FhNRT2.1 for nitrate, FhPHO1.1 and FhPHO1.2 for phosphate, and FhHAK5 and FhKT2 for potassium. Ion analysis confirmed that treated roots accumulated significantly higher levels of nitrogen, phosphorus, and potassium. Interestingly, the mechanism appears to differ from that reported in Arabidopsis, where similar molecules act through G protein-coupled receptor (GPCR) signaling—no such response was observed in citrus, suggesting a distinct pathway.
The authors said, “We were surprised to find that a single bacterial signal could coordinate the uptake of multiple nutrients at once. Instead of acting like a hormone, PGPHL seems to flip a master switch that tells the root to bring in more of what it needs.” They added, “What excites us most is that this isn't just a lab phenomenon—it works in the field, across different crops and soil conditions.”
The implications are substantial. Unlike live PGPR, which often suffer from poor viability, storage instability, and inconsistent field performance, PGPHL is a small, stable molecule that can be synthesized and applied directly. Field trials demonstrated that a 10 μM PGPHL solution increased pepper yield by 20.79%, mustard biomass by 14.54%, and celery biomass by 18.31%. This broad-spectrum efficacy suggests PGPHL could be developed into a new class of plant growth stimulants and biofertilizers, offering farmers a reliable, cost-effective tool to reduce chemical fertilizer dependence while boosting productivity. The team has already developed a synthetic route for large-scale production, bringing this microbial signal one step closer to the field.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhag071
Funding information
This work was supported by the National Key Research and Development Program of China (2024YFD2300800), the National Natural Science Foundation of China (32502615), Hubei Fruit Industrial Technology System Project (2025HBSTX4-08), the Fundamental Research Funds for the Central Universities (2662025YLPY010), Hubei Provincial Citrus Industry Chain Project (2024), Guangxi Science and Technology Major Project (GK AA23062085).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.
Horticulture Research
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Rhizobacteria promote plant growth via secretion of N-(3-oxooctanoyl)-L-homoserine lactone
28-Feb-2026
The authors declare that they have no competing interests.