Frequently Asked Questions

Rice Azospirillum

Roots can be engineered to express different colors that are linked to specific gene function

What are Biosentinels?

Biosentinels also known as bioindicators, ambiosensors, Sentinel plants, bio-reporters, biomarkers, “Smart” plants, and biosensors, are in vivo reporter systems applied to resolve a specific field problem, are live organisms that their sole purpose is to mark an event at a specific time and in a particular microenvironment.  Biological indicators include natural organisms that are used to monitor the atmosphere or soil. Some examples include

  • mosses, which are used as bioindicators for heavy metal deposition in the atmosphere in Finland,
  • native plants species that are used to monitor airborne fluorides in Europe and USA,
  • lichens, which are used as bioindicators of air pollution in Italy,
  • honeybees and their products, which are explored as potential bioindicators of environmental pollution also in Italy, and
  • bacteria that were used to monitor toxic metals in soil.

Engineered bioindicators consist mainly of transgenic plants that are designed to monitor levels of specific contaminants in natural resources such as soil, water or sediments. Specific examples include transgenic plants whose leaves turn from green to red after 3-5 weeks exposure to nitrogen dioxide gas, making the plants useful bioindicators of landmines (, transgenic Arabidopsis plants that are metal specific bioindicators5, transgenic Arabidopsis plants that monitor their own phosphorus status6, and transgenic Arabidopsis that were explored as sensitive bioindicators of nuclear pollution caused by the Chernobyl accident.7

What is unique about this particular project?

This project goes beyond the model system approach. It seeks to develop specifications for biosentinel plants (rather than prototypes) and modules (component parts), if you will, that can be accessed fairly, assembled or disaasembled and reassembled again by various end users based on their own needs.  CAMBIA’s intention not to claim ownership for this stratigic project, instead provides some modules and expertise to facilitate project development by various collaborators and institutes.  Our ultimate aim is to enable informed decision-making and maximization of limited resources by farmers themselves (for more details, see Jefferson, R.A. (1993) ‘Beyond model systems: New Strategies, Methods, and Mechanisms for Agricultural Research‘, Annals of the New York Academy of Sciences 700: 53-73).

The community approach to this project, as opposed to a single lab for a single crop, may bring a deliverable mechanism to lab outputs and link them to address field challenges in heterogeneous environments and unpredictable agricultural ecosystems.

Our approach to develop modular parts that can be combined in various ways is also supported by a delivery mechanism that is royalty-free and under a BiOS license, to ensure open access and fair use by local groups wishing to develop their own biosentinel systems.  The project began by voluntary contributions but now is supported through funding by the Lemelson Foundation, and we hope that your direct and indirect contributions will enrich it and sustain it as a public good.

What is the modular strategy for the BioForge bioindicators project?

To engineer and develop a bioindicator plant, our approach envisions that various modules can be recombined for different crops and settings:

  1. Identification of the potential bioindicator plant: what plants will grow well in the context of the field problem that you are trying to solve? Does the proposed indicator plant enter the food chain or not? What are the consequences of either option?Some of the desired characteristics for an indicator plant:
    • relevance to the problem and crop-growing context;
    • easily transformable;
    • can be sterile, if need be; and
    • ideally, it already contains the appropriate sensor or a homologue (which is helpful from a regulatory perspective).
  2. Sensor identification: preferably one or more regulatory element(s) or gene(s) that are specifically induced or up-regulated in response to the constraint the bioindicator is desired to address, such as soil available concentration of a nutrient. Many such sensors are found in the published literature and more may be found via interactions with the BioForge user community.
  3. Engineering the sensor with a known reporter system, such as GUS or GUSPlus, GFP, etc. The choice will depend on interactions with the type of sensor used, the position in the plant where the response must be visualised, and its mode of regulation.
  4. Regulation of the time and duration of the response: inducibility, how long the system is “turned on” (i.e. the signal persists through to plant senescence or it is turned on and off based on the initiation for perhaps a few days to provide the needed response).
  5. Detection: this can be as simple as an induced change in the color of the leaf/stem or productive organs, so that the response will be obvious and easily detected by inexperienced persons. Alternatively, it can be designed to induce a strong unusual smell to serve the same purpose. Such sensory systems are available, but they need to be tuned to the purpose of this project.

How will the community access and help in the innovation of plant bioindicators?

The scientific and IP teams at CAMBIA have developed some initial modules (such as the TransBacter and GUSPlus technologies) and will continue to further develop much needed modules. But also we would welcome contributions, suggestions, new ideas or tools that you would like to share under an open source business models.  All the available technologies will be available under a BiOS license .

We also expect, with the assistance of the community, to develop for each module one or more technology landscapes or “Freedom to co-operate” analyses for those components of modules that are not in CAMBIA’s “protected commons” yet.

Communities interested in customizing the modules to develop a preferred bioindicator can then acquire the parts cost-free, assemble and develop the product and test it under local conditions. Within the community of BiOS licensees, shared successes and failures will be discussed and reported, and improved versions of the modules/products will continue to be widely available as public goods.


  1. Poikolainen J, Kubin E, Piispanen J, Karhu J (2004) Atmospheric heavy metal deposition in Finland during 1985-2000 using mosses as bioindicators?. The Science of the Total Environment 318 (1-3): 171-185.
  2. Weinstein LH, Davison AW (2003) Native plant species suitable as bioindicators and biomonitors for airborne fluoride, Environmental Pollution 125 (1): 3-11.
  3. Conti ME, Cecchetti G (2001) Biological monitoring: lichens as bioindicators of air pollution assessment: a review, Environmental Pollution 114 (3): 471-492.
  4. Ramanathan S, Ensor M, Daunert S (1997) Bacterial biosensors for monitoring toxic metals. Trends in Biotechnology 15 (12): 500-506.
  5. Krizek BA, Prost V, Joshi RM, Stoming T, and Glenn TC (2003) ‘Developing transgenic Arabidopsis plants to be metal-specific bioindicators’, Environmental Toxicology and Chemistry  22 (1): 175-181
  6. Hammond JP, Bennett MJ, Bowen HC, Martin R. Broadley MR, Eastwood DC, May ST, Rahn C, Swarup R, Woolaway KE, and White PJ (2003) ‘ Changes in gene expression inArabidopsis shoots during phosphate starvation and the potential for developing smart plants‘. Plant Physiology 132: 578-596.
  7. Kovalchuk I, Kovalchuk O, Arkhipov A, Hohn B (1998) Transgenic plants are sensitive bioindicators of nuclear pollution caused by the Chernobyl accident. Nature Biotechnology16: 1054-1059.