The plant need to perform a number of biochemical reactions to maintain the complex phenomena called life. Almost every one of these reactions is controlled by biological catalysts known as enzymes. Almost all enzymes are proteins. In turn, the information to synthesize every one of the enzymes is present in small segments of DNA called genes. Every gene from eukaryotic organisms is basically formed by two sections: a promoter and an encoding region. The encoding region is the part of the gene which is read and translated into proteins. By other side, the promoter region is the regulatory section of the gene. This is the part of the gene which controls in what part of the organisms the protein is going to be present, how much of the protein will be present, when the protein is going to be made and what kind of stimuli will trigger the synthesis of the protein. Among the stimuli which can induce the synthesis of proteins we can mention the different stages of development of the organisms, the light, wound, salinity stress, hydric stress, heat stress, cold stress, infections by bacteria and fungi, lack of oxygen, and basically every change in either physiological status of the plant or environmental one can trigger the synthesis of proteins. From the above mentioned, the knowledge of the promoter properties is important to understand the function of the gene in the physiology of the plant.

By other side, there are tools derived from the DNA recombinant technology which allows to change parts of a gene. In this way, it is possible to have a gene created with a promoter from a virus controlling the natural encoding region of the gene. This type of gene is called chimera (from the Greek mythological creature created with parts from different animals). Although chimeras are not natural genes, they are important tools during the study of the characteristics of the real gene. Chimeras once created can be put back in the plant to study its behavior.

In this work, a chimera was created by joining together the natural promoter of a gene which is responsible for synthesizing an enzyme called pectin methylesterase and a protein which is easy to quantify and locate. That is, it is easy to known how much of the protein exists at one point in time and in what part of the plant is being synthesized. This protein is known as beta-glucuronidase.

The chimera was inserted in both tobacco and tomato plants, creating what is known as transgenic plants. These two group of transgenic plants were used to study the characteristics of the promoter region of the gene encoding the enzyme pectin methylesterase.

The studies in the transgenic plants showed that the promoter is active in all parts of the plant, including roots, stem, leaf, flower and fruit. However, we did not find activity of this gene in pollen grains.

We also found that all the promoter region was needed to have the same amount of protein synthesized because the removal of one part of the promoter region caused a reduction in the amount of protein synthesized. This behavior was similar in root, stem and leaf of the transgenic plants.

Besides of the studies in the plant, modern tools allows to study the sequence of the genes. We know exactly the composition of the components of the promoter we are studying and in what order these components are arranged, something known as the sequence. Besides of that, the study of the sequence of hundreds of different promoters had found that there are sequences in common between promoters which responds to the same kind of stimuli called boxes. In this way, promoters activated in response to light, physical damage, pathogen attack, etc., usually bears in the sequence what is called an specific box. A box is basically a sequence of 5 to 10 bases. There are light responsive boxes, hormones responsive boxes, wound responsive boxes, fruit ripening response boxes, hidric stress boxes, heat response boxes, etc. The finding of one of these boxes in the sequence of a promoter, suggest that this promoter most likely is activated by the corresponding stimuli. That is, if the box was found in wounding responsive promoters, then, the promoter under study will probably be a wounding responsive promoter.

There are software developed which scans the sequence of a promoter to find these specific boxes we mentioned above. It turns out that we also did the study of our promoter and found three light responsive boxes.

Up to now, we know the different characteristics of the promoter, namely: It is active in all plant tissues except pollen, the whole region is needed to have the right amount of protein and in the promoter there are elements that suggest that this promoter can be active in response to light. It is quite possible that the removal of some parts of the promoter can eliminate some of the elements present and in turn its distinctive characteristic of light response.

With all the information mentioned above, we are ready to speculate about the function of the gene pectin methylesterase. First of all, this gene is most likely playing an important role in the normal development of the plant. Furthermore, it is quite possible that this gene is also playing a role in the plant responses to changes in the light of the environment. This is specially important considering that the plant’s responses to the light includes changes in the growth of some parts of the plant in order to get the plant closer to the light source. In turn, changes in plant growth implies alterations in the hard structures surrounding the cells. Indeed, in those structures is where the pectin methylesterase catalyzes the changes.

In summary, it is possible that the enzyme pectin methylesterase, which is able to produce some alterations in the hard structure which gives support to the plant cell, plays a role in the normal development of the plant and in the plant’s responses to the light.

At this point, it is important to make clear that the conclusion above mentioned needs still more experimental evidence to be scientifically probed. However, the strategy depicted above was the one followed by the real scientific paper from which this document is derived.