Need for Protein Detection

Before exploring the details of protein detection topics, first consider scenarios when identifying the presence of a protein would be useful. For example, the use of modern agricultural biotechnology methods has led to the development of crops that exhibit unique agronomic characteristics. These crops have novel pieces of DNA inserted into their genome that code for the production of unique proteins. The transgenic DNA and protein can be found in a variety of tissues of these plants, including seeds and grain, and even foods derived from them.

There are situations where traits need to be detected in a growing plant in the field or greenhouse. In the case of corn borer resistance or herbicide resistance in genetically engineered crops, it may be desirable to use some test to detect the expression of the protein or the presence of the new gene. Good examples of this would be when a scientist needs a quick test to see which of their plants express the gene, when an agronomist needs to know if a plant with corn borer feeding damage really does make the Bt protein and is being attacked by resistant borers, or if a herbicide applicator needs to be sure of where the rows of Roundup Ready soybeans start in the field.

In another scenario, some food consumers question the safety of biotech derived crops. As a result, a few countries have enacted laws mandating that foods containing ag biotech ingredients above a specified threshold must be labeled as such. The threshold concentration specified in these regulations is defined in terms of the percentage of genetically modified organisms (GMO) present in the food or ingredient. These importing countries need a test available for measuring protein levels in grain shipments and food products before accepting them into their borders.

Laboratory methods have been developed that could be used in these real-life situations which detect either the transgene or the protein encoded by the transgene (Fig. 1). Details of DNA detection for a specific gene are described at length in the online lesson Real Time PCR-Some Basic Principles. This lesson, however, will focus on protein detection applications in GMOs, but keep in mind, the general principles are the same for other protein detection uses as well. For example, clinical diagnostics for HIV, hepatitis, drug monitoring, pregnancy, etc. all rely on protein detection. Similarly protein detections for the presence of microorganisms, allergens, toxins and pesticides are routinely employed in foods.

Figure 1 Diagram illustrating that a GMO can be detected at both a gene and protein level.