The following points highlight the three potential risks associated with virus. The risks are: 1. Environmental Issue 2. Health Issue 3. Virus Overcoming Transgenic Resistance.
Virus: Potential Risk # 1.
Environmental safety issues have also been expressed with regard to the transfer of virus genes from transgenic crops into compatible plant species through pollination. It is not impossible that an otherwise susceptible plant could become resistance to virus infection upon successful hybridization.
As a consequence, hybrid progeny could have an increased fitness and eventually become more competitive in their habitat. This even may give birth to some highly potent weeds which can grow rampantly taking over the commercial crops.
Virus: Potential Risk # 2.
Effects of virus-resistant transgenic crops on human health relate essentially to allergen city in terms of the properties of proteins encoded by virus gene segments expressed in transgenic plants. Theoretically, virus-transgene protein products can have stretches of amino acid sequences that are identical to potential epitopes of allergen proteins.
As a consequence, transgenic plants expressing virus-gene fragments could promote allergy in people coming in contact with the products of such transgenic plants.
Virus: Potential Risk # 3.
Virus Overcoming Transgenic Resistance:
Some virus strains are able to overcome engineered resistance because RNA silencing is a defense mechanism based on nucleotide sequence identities. Resistance is more likely to be achieved against virus strains with high sequence homology to the strain(s) from which transgenes are derived than those that are most distantly related. In addition, viruses encode some proteins that can act as suppressors of RNA silencing.
This means that viruses can counteract the plant’s defense mechanism by interfering with some key steps of the antiviral pathways that lead to resistance. Also, the plant developmental stage and features of virus-derived transgenes, among other factors, can influence the effectiveness of RNA silencing.
In other words, activation and regulation of the antiviral pathways of RNA silencing is dynamic. Therefore, monitoring the introduction of virus-resistant transgenic crops and eventual emergence of new viral strains is key to maximize the effectiveness and durability of engineered virus resistance.