In a breakthrough discovery poised to revolutionize sustainable agriculture, researchers led by Prof. Dr. Thomas Ott at the University of Freiburg have unveiled critical molecular mechanisms that govern the symbiotic relationship between leguminous plants and nitrogen-fixing bacteria. This groundbreaking study elucidates how a previously poorly understood protein, SYFO2, orchestrates the entry of beneficial rhizobia bacteria into plant root cells, facilitating the vital process of biological nitrogen fixation. Published in the esteemed journal Science, this research holds profound implications for reducing dependence on synthetic fertilizers and enhancing crop productivity worldwide.
Nitrogen is an essential nutrient for plant growth, yet most plants are unable to fix atmospheric nitrogen directly. Leguminous plants, such as peas, beans, and clover, uniquely engage in an evolutionary alliance with soil-dwelling rhizobia bacteria. These bacteria inhabit specialized root structures called nodules, where they convert inert nitrogen gas into bioavailable ammonium, effectively “fertilizing” their host. Although this symbiosis has been known for decades, the precise cellular and molecular mechanisms that enable bacterial infection and nodule formation have remained elusive—until now.
Central to the newly discovered infection pathway is SYFO2, a formin protein localized in nanodomains of plant root cell membranes. SYFO2 acts as a pivotal gatekeeper, modulating the actin cytoskeleton within root hair cells. This cytoskeletal rearrangement is essential as it facilitates the engulfment of rhizobia into infection threads, tubular structures that guide bacteria inward. By controlling these structural changes, SYFO2 effectively switches the plant’s response from bacterial detection to acceptance, allowing symbionts a safe passage into the cellular interior where mutualistic interactions commence.
The discovery was achieved through a combination of high-resolution live-cell imaging, molecular biology, and genetic manipulation. Notably, researchers demonstrated that manipulating the expression of the transcription factor NIN, a master regulator of nodulation, activated the tomato’s endogenous SYFO2-like protein. This activation enabled infection-like processes in tomato—a non-leguminous, solanaceous crop that does not naturally form nitrogen-fixing symbioses. This finding suggests an exciting avenue for bioengineering nitrogen fixation abilities in a broader range of crops beyond traditional legumes.
“This work identifies the molecular foundation underlying a critical step where plants open the door for rhizobia to enter,” explained Prof. Ott. “Our data show how SYFO2 initiates the reorganization of the actin cytoskeleton, converting root hairs from simple barriers into gateways for bacterial infection. Understanding and harnessing this switch is fundamental for future efforts aimed at engineering nitrogen fixation in important food crops.”
While SYFO2’s role in rhizobial infection is novel, the protein was also found to be involved in more ancient plant–fungal symbioses, specifically mycorrhizal relationships. Mycorrhizal fungi colonize plant roots to enhance nutrient and water acquisition, a partnership established hundreds of millions of years before legume-rhizobia symbioses evolved. The dual role of SYFO2 in both fungal and bacterial interactions reveals evolutionary plasticity, where plants have co-opted existing molecular machinery to establish new symbiotic partnerships.
The ENSA (Enabling Nutrient Symbioses in Agriculture) project, supported by Gates Agricultural Innovations, provided the collaborative framework for these findings. By bringing together expertise from plant cell biology, genetics, and ecology, the project seeks to unlock the full potential of symbiotic nitrogen fixation to reduce agricultural reliance on synthetic fertilizers. Fertilizers, while boosting crop yield, cause significant environmental issues including groundwater contamination and greenhouse gas emissions. Engineering nitrogen-fixing capabilities into staple crops could dramatically lower these negative impacts.
Methodologically, the study combined protein localization studies using fluorescence microscopy with mutant analyses and transcriptional regulatory assays. The researchers used legumes such as Medicago and Lotus as model systems before validating the findings in tomato plants. These experimental approaches allowed precise dissection of SYFO2 function at the cellular level and its regulation at the transcriptional level by the NIN transcription factor.
Importantly, this research not only advances fundamental understanding of plant–microbe interactions but also provides promising new tools for synthetic biology. By transferring or activating symbiosis-related genes like SYFO2 in non-legume crops, scientists could potentially engineer these plants to autonomously fix nitrogen—eliminating a critical yield-limiting nutritional constraint. Such innovations align with global goals for sustainable agriculture and food security under climate change pressures.
The implications of this study are vast. Beyond immediate agricultural applications, uncovering how proteins such as SYFO2 locally regulate actin dynamics sheds light on fundamental plant cell biology. The discovery opens avenues for exploring how similar nanodomain-localized formins and cytoskeletal regulators function in other developmental and environmental responses. Additionally, identifying the modular genetic control elements of symbiosis enables more targeted biotechnological interventions with fewer off-target effects.
Prof. Ott emphasized, “Our findings mark a significant step forward in deciphering the language plants use to negotiate symbiotic entry points. By understanding these molecular dialogues, we move closer to reprogramming crops for improved nutrient-use efficiency and resilience. The ultimate goal is to develop new agricultural strategies that harness nature’s own innovations for a sustainable future.”
The study titled “Nanodomain-localized formin gates symbiotic microbial entry in legume and solanaceous plants” was published in Science (Volume 391, pages 1036–1045) with DOI: 10.1126/science.adx8542. It catalyzes a paradigm shift from classical fertilizer-dependent agriculture toward an era of precision symbiotic engineering, proving once more how integrative biological signaling research can address some of humanity’s most pressing challenges in food production and environmental stewardship.
Subject of Research:
Molecular mechanisms underlying symbiotic nitrogen fixation and microbial entry in legumes and solanaceous plants.
Article Title:
Nanodomain-localized formin gates symbiotic microbial entry in legume and solanaceous plants.
News Publication Date:
June 2026
Web References:
https://doi.org/10.1126/science.adx8542
References:
Qiao, L. et al. (2026). Nanodomain-localized formin gates symbiotic microbial entry in legume and solanaceous plants. Science, 391(1036–1045).
Image Credits:
Not provided
Tags: actin cytoskeleton modulation in plant rootsbiological nitrogen fixation processcrop productivity enhancement through symbiosismolecular mechanisms of nitrogen fixationnitrogen-fixing bacteria infection pathwayprotein role in plant-microbe interactionsreducing synthetic fertilizer dependencyroot nodule formation in legumessustainable agriculture innovationsSYFO2 protein in leguminous plantssymbiotic relationship with rhizobiaUniversity of Freiburg plant research
