Bacterial speck of tomato, caused by Pseudomonas syringae pv. tomato (Pst), poses a serious threat to tomato production worldwide. Once visible symptoms appear, control is difficult, and the disease causes irreversible yield and quality loss. Existing early detection methods, however, are barely able to meet practical needs. Colony culture is time-consuming, while molecular detection methods like PCR rely on professional equipment and technicians with high costs (see more on the Description page).

There is an urgent need for an economical, efficient, and easy-to-operate detection device in agricultural production to fill the current gap.

Why PROTATO?

PROTATO can be of great use to achieve fast detection with low cost and labor input. Specifically, compared with other existing detection methods, PROTATO has the following advantages:

  • Reliable early detection. Dependable early-stage pathogen identification and enabling timely intervention.
  • High portability and practicality. PROTATO is designed for convenient on-site use and aligns with real-world agricultural application scenarios.
  • Low cost and high accessibility. Features economical hardware and simple operation, making it easily accessible to a wide range of users.

From Laboratory to Field: System Design and Feasibility

1. Cell-free Protein Sensing System

PROTATO functions entirely in a cell-free environment, composed of purified or recombinant proteins. This design eliminates living organisms and thus removes the biosafety risks associated with genetically modified materials.

At the molecular level, PROTATO detects two virulence factors secreted by Pst — AvrRpt2 protease and Coronatine (COR). Using a split-protein logic gate, the biosensor produces an output only when both effectors are present, achieving specific and reliable pathogen identification.

After receiving feedback from agricultural technicians, we replaced our initial split-GFP design with a split trehalase (TreA) system. Trehalase converts trehalose into glucose, and the resulting glucose concentration can be conveniently detected using a commercial glucometer. This transformation — inspired by farmers’ comparison with “blood glucose meters” — made the detection process faster, cheaper, and more familiar to users.

2. Hardware Integration

To bridge the gap between laboratory biosensors and practical agricultural use, we developed the Protato Kit — a compact, all-in-one device integrating collection, grinding, reaction, and detection.

The upper section is a metal grinder enclosed in a resin shell, while the bottom orange section serves as a sealed reaction chamber containing pre-prepared reagents. During grinding, tomato leaf tissue is crushed, releasing potential pathogen effectors into the buffer. Afterward, the mixture reacts in the sealed chamber, and the glucometer electrode cap reads the glucose output.

The device’s modular design ensures ease of operation, safety, and reusability. The entire detection workflow can be completed within 30 minutes, requiring no electricity, laboratory setup, or technical training.

Stakeholder and User Feedback

To ensure PROTATO meets real agricultural demands, we conducted multiple rounds of field investigation and expert consultation with farmers, agricultural technicians, and plant pathologists. These interactions helped us shape both the biological design and the feasibility of our system.

Understanding Real Needs

From conversations with tomato growers across different regions, we learned that bacterial speck disease is especially severe in greenhouse cultivation, where warm and humid conditions accelerate its spread. Farmers emphasized that prevention is more effective than treatment, yet early detection tools are currently unavailable. Most rely on visual inspection and experience, often missing the best window for disease control.

These findings validated the necessity and feasibility of our biosensor — a low-cost, portable, and intuitive diagnostic tool for use directly in the field.

Design Iteration and Optimization

Feedback from agricultural practitioners inspired several key improvements:

  • Output signal transformation: Farmers compared our system to blood glucose meters, which led us to redesign the output from fluorescent protein to split trehalase, allowing glucose-based readout compatible with glucometers.
  • Hardware optimization: Practical users preferred a compact and enclosed system for field use rather than per-plant deployment. This guided our modular “Protato Kit” design integrating collection, grinding, and detection in one device.
  • Sample selection: Since early symptoms first appear on leaves, we focused on leaf extracts as testing material.
  • APP integration: Modern farms and distributors highlighted the need for digital result recording. We thus planned a mobile APP to display results and store data for long-term monitoring.

Expert Guidance

Plant biologists and synthetic biology specialists provided crucial insights into system feasibility and biosafety. Their advice refined our effector protein screening, verified substrate compatibility in the glucose detection system, and confirmed that our cell-free design avoids risks associated with living modified organisms.

Experts in plant pathology also pointed out the limitations of existing molecular methods (PCR, RPA), reinforcing PROTATO’s value as a field-friendly alternative.

Field Validation and Reflection

Field visits to different types of farms — including traditional soil cultivation and hydroponic smart agriculture — allowed us to validate PROTATO’s real-world potential. We found that while high-tech farms already use automated monitoring, they still rely on visual diagnosis, whereas small- and medium-scale farmers urgently need affordable early detection solutions.

These insights shaped our implementation focus:

  • ensuring affordability and accessibility for traditional farms,
  • maintaining precision and safety under diverse conditions, and
  • integrating our system with digital tools for future scalability.

Through this iterative process, we summarized our principle “Beyond Lab” — grounding synthetic biology innovation in real social and agricultural contexts.

Safety and Environmental Considerations

PROTATO's cell-free system and sealed reaction cartridges ensure no release of genetic material or pathogens into the environment. Residual proteins are inactivated using guanidine hydrochloride solution, preventing any contamination. Device components are made of recyclable materials (resin, silicone, stainless steel), allowing safe reuse and eco-friendly disposal.

This design supports safe, decentralized detection even in open-field conditions, aligning with biosafety and sustainability goals.

Feasibility and Cost Evaluation

Each PROTATO test takes less than 15 minutes and costs under USD 2 per reaction. The device can be mass-produced using simple molding or 3D-printing techniques, and reagents can be lyophilized for long-term storage and transportation.

Its ease of use, low cost, and portability make PROTATO suitable for both smallholder farmers and agricultural cooperatives.

SWOT Analysis

We have made an overall SWOT analysis on PROTATO, helping us to find out the advantages and weaknesses.

Strengths

  • Reliable early detection.
  • Portability and practicality.
  • Low cost and high accessibility.

Weaknesses

  • Consistency of protein activities in our system is hard to guarantee.
  • It can only achieve qualitative detection instead of providing quantitative data. Usually, it is necessary to use other detection methods for support.
  • The adaptability and stability of the system in real field environments still need further verification.

Opportunities

  • A market gap in the early detection of bacterial disease in plants.
  • Replacing the system's input effector protein provides possibilities for the detection of different pathogens, extending use to more crop diseases and boosting technical versatility and value.
  • Bactericidal treatment can be harmful to human health and the environment, making early detection systems vital for plant disease management.

Threats

  • Security and accuracy in use.
  • New methods may face low acceptance by farmers and promotion difficulties.
  • Other detection methods available (such as PCR) can achieve more accurate detection compared.
  • The market supervision of synthetic biology products is not well-established.

Methods of Implementation

Improvement Directions

  • Explore replaceable effector proteins as input signals to expand the detection coverage.
  • Address issues of large-scale protein production for PROTATO, promoting the transformation of the technology from the laboratory stage to the mass production stage.

Marketing and Promotion

  • Investigate more about the target market. Understand the needs, preferences, and behavioral characteristics of potential customers in these fields.
  • Figure out the target audience. We aim to establish PROTATO as a convenient, affordable, and portable detection method for various bacterial diseases in plants. Furthermore, different modes of agriculture have different demands for the design of our device.
  • Conduct marketing activities. Execute marketing strategies and engage in marketing activities, such as related exhibitions and conferences, and utilize social media and graphic design to increase product visibility and appeal.
  • Regular evaluation and adjustment. Regularly assess the effectiveness of marketing strategies and make necessary adjustments and optimizations based on market feedback and competition. Maintain flexibility and adaptability to ensure the ongoing effectiveness of marketing strategies.

Policy Advocacy

In China, supporting policies for synthetic biology detection technologies like PROTATO are still incomplete. To accelerate such technologies from labs to practical use, advocating policies is key:

  • Engage with regulatory authorities. Initiate dialogues and engage in discussions with relevant regulatory authorities to raise awareness about the potential benefits of synthetic biology products like PROTATO.
  • Collaborate with synthetic biology associations and organizations. Gather our competencies to advocate for policy reforms and regulations that support the development and commercialization of synthetic biology products.
  • Educate the public. Conduct awareness campaigns and educational initiatives to inform policymakers, stakeholders, and the general public about synthetic biology, its applications, and the potential benefits it offers. Highlight the safety measures and ethical considerations in the development and use of synthetic biology products.
  • Foster international collaboration. Engage in international collaborations and exchanges to learn from the practices and experiences of other countries in regulating and promoting synthetic biology products.

Conclusion

Through continuous dialogue with farmers, technicians, and researchers, PROTATO has evolved from a laboratory prototype into a field-oriented, safe, and cost-effective detection system. It represents a step toward bridging synthetic biology and sustainable agriculture, empowering farmers with early, accessible, and reliable pathogen detection — protecting both tomatoes and livelihoods.

 

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