Examples of BioSentinels

Aresa_Sand_plants

Weed exhibiting red-purple colour due to the presence of TNT in the soil (Photo provided by Aresa)

One significant aspect of the innovation will be identification of indicator species appropriate to the local cultivation system, sensitive to the condition of interest, and able to provide an observable signal.

In 1998, Kovalchuk et al., Bioindicator plants to detect nuclear pollution, engineered Arabidopsis plants to analyze the influence of chronic irradiation from the environment of the Chernobyl exclusion zone, on the stability of plant genomes. In this example, bioindicator plants were shown to be an effective indicator of change within the surrounding environment.

Another example encompasses research conducted by Aresa, a private company originally based at the University of Copenhagen, that is marketing bioindicator plants commercially. Aresa genetically engineered a weedy plant with a gene that produced a red-colored product when the gene’s expression was induced by a receptor as a breakdown product of TNT. This allowed the plant to become a potential field biosentinel to alert about the presence of land mines.

Proof of concept is thus established for Biosentinels.  For example, the underlying mechanism by which the color changes from green to red in the Arabidopsis plants, occurs is via an altered regulation of the natural pigment biosynthetic pathways in the plants.  The genetically engineered plants could then be modified in a way that allows these plants to turn red-purple if triggered by TNT in the soil. The field applicability of such a technology remains to be evaluated.

Shown below2 at left is a photo of a soil tray planted with the engineered bioindicator seed in which the upper right quadrant of the soil has been drenched with liquid TNT. The photo at the right indicates the size of isolated plants.

Aresaphotos

Because CAMBIA’s project goes beyond a model system approach,  we envision that the real field problems are going to be complex and variable and thus through the provision of various modules, the coordination of their accessability by an open source approach, and the evaluation of their potential field applicability, a more efficient and enabled innovation can be achieved, with the production of prototypes, by the end-users themselves.

For example, scientists have identified gene products that might be applied to measuring iron and phosphate levels and heavy metals in soil3, and Aresa has announced a plan to commercialize biosentinels for bioremediation4.  Unfortunately, in the iron and phosphate plant sentinel prototype systems, the effects of the measurement are seen in the roots5 (not readily visible to the farmer) or as a very slow change in the shoots6 (timing that may not facilitate effective response measures), or like in the case of phosphate, we do not know yet the rate limiting step that determines level of phosphate in the plant.

New examples of detection methods include a color change on a de-greened background (Medford et al.), a shape change or a texture change, such as the presence or absence of trichomes. Such changes might appear in leaves or stem segments produced only in plastochrons immediately associated with the stress, and leaf or stem segment production would revert to normal in sectors produced after the stress passes.

If you have ideas about such changes and how to effect them and you are willing to contribute or participate in this project, please email us.

References

  1. Images are used with permission, from Aresa’s website, www.aresa.dk
  2. Vert G, Grotz N, Dedaldechampa F, Gaymard F, Guerinot ML, Briat J-F, and Curie C (2002) ‘IRT1, an Arabidopsis transporter essential for iron uptake from the soil and for plant growth’. Plant Cell 14: 1223-1233;
  3. www.aresa.dk
  4. Vert et al. ibid.
  5. 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 in Arabidopsis shoots during phosphate starvation and the potential for developing smart plants’. Plant Physiology 132: 578-596.