The solution: plants
NavarraBG proposes plants as a way of sensing substances of interest as an ecological alternative to the electric sensors used nowadays. Working with plants has multiple advantages, they produce the oxygen we breathe, maintain the soil, regulate humidity and contribute to climate stability. Also, the use of plants as biosensors instead of the current devices is an alternative option much more economical and easier to transport.
In addition, plants as biosensors have positive impact on the human mental health. Plants can improve the human psychology while they develop the work that they have been designed for. If we take as an example sensing the air quality by measuring the concentration of CO2 in the ambient, a sensor plant can detect high CO2 concentration while it improves the mental health of the people that usually around it by creating a bond between the plant and the human beings.
Another benefit of using plants is that we need a new way of sensing different substances of commercial, social and health interest due to the damage that using electrical sensors over a long period can do to the ecosystem. This is why plants are the perfect solution, as they are organic, they do not generate pollution when they become obsolete, and they do not require electricity to work or be produced. In addition, they could be reproduced by seeds, and you will produce more biosensors with no economic and ecological waste (see “The process of modifying a plant”).
The process of modifying a plant
The process of modifying a plant could be done by two ways, transitory and permanent transformation. The first one is a method of temporarily introducing foreign DNA into a plant cell and the DNA is not integrated into the host genome. In a permanent transformation, the foreign DNA taken up by the host is fully and permanently integrated into the host genome and the genetic modifications are present in further generations.
One time the permanent transformation has be done, it is the time to know if the plants have correctly modified. To achieve this, we have different options.
Phenotyping: this is only possible if the modifications make a significative change in the phenotype of the plant such as a change of the colour (with the RUBY cassette which turn the plant red) or a fluorescence when the plant is exposed to UV light (with the reporter eYGFPuv the plant shines when is exposed to UV light). This way could help us to select which plants have been correctly modified quickly.
Antibiotic selection: once we have obtained the transgenic seeds, we must know if they are modified. If the plants have resistance to a specific antibiotic, they will growth in a plate supplement with this antibiotic. In our case the modified plants are resistance to hygromycin, so in a plate that contains hygromycin, only will grow the plants with the correct modification.
PCR selection: once we have selected the seeds with the correct resistance to antibiotics, we should make a PCR to confirm that the plants have the correct construction. In our case, the promoters come from Arabidopsis thaliana, the reporter RUBY from Beta vulgaris and the eYGFPuv from Chiridius poppei). As a result, we select a primer from the promoter and other primer from the reporter, and if the plant is modified, we will get a PCR product, if the plant is WT the PCR will not be positive.
The promoters
In our project we use promoters that are induced at high concentrations of CO2 from Arabidopsis thaliana.
RUBY cassette
We use as a reporter the RUBY cassette because this reporter can be seen immediately (the plant turns into a red colour). This characteristic is very important to our project, due to the aim that creating a biosensor that is completely independent from technology. RUBY genes come from the Beta vulgaris.
As the RUBY cassette comes from the Beta vulgaris we need to know that the Arabidopsis thaliana is not negatively affected by the proteins produced by the RUBY genes. We compare if the Arabidopsis thaliana wild type have any difference with the Arabidopsis thaliana modified with RUBY.
PEST sequence
An important characteristic of a biosensor is the capability to return to a normal aspect once the exposure to the stimulus has finished. So, we decided to use the degradation sequence called PEST. This is a sequence of amino acids that are in proteins of a short half-life of different plants. We add this sequence to a gene reporter to study its half-life. In our project we make a construction that contains a constitutive promoter (p35S), a reporter that make the plant shine when is exposed to UV light (eYGFPuv), the degradation sequence (PEST) and the terminator (NOS).
For other teams
Our team has made a construction that could be useful to other teams since it can help another team make a plant capable of detecting different substances of interest with only a few steps. Other teams could change the promoter of the construction by another promoter that would be inducible by the substance that they are working with, as a result, they would obtain a completely functional biosensor that detect the substance they want to detect.
The specific attributions of plants
Plants are organism that have an amazing quantity of advantages and specific attributions that could be so much useful on the synbio, as a result, plants could be so much useful on the society, related with economy, health and ecosystems.