The European Food Safety Authority (EFSA) discovered a viral sequence in commercial GMO crops.  The viral sequence encodes a significant fragment of a viral gene, and the viral gene in question is called Gene VI (Podevin and du Jardin 2012). In most part, viral genes function to disable the host defense mechanism in order to initiate pathogen invasion. Viral gene such as Gene VI can be found in regulatory sequence of a constitutive cauliflower mosaic virus promoter (CaMV 35S promoter).  CaMV 35S promoter is a promoter used in most Agrobacteria-mediated vectors/cassette constructs used in the transformation process of any crop.  Based on Podevin and du Jardin’s assessment of 86 unique transgenic events commercialized to-date in the US, 54 transgenes contain Gene VI sequence.  The finding includes Roundup Ready soybeans (40-3-2) and MON810 maize. The gene is also found in the NK603 maize which was recently linked to tumors in rats (Seralini et al. 2012).

Gene VI is a multifunctional gene. Thus far, there are four known functions of gene VI in the viral infection cycle. Gene VI is associated with viral particles assembly. Secondly, Gene VI is an inhibitory machinery, a cellular anti-pathogen defense RNA silencer (Haas et al. 2008). Thirdly, Gene VI encodes active trans-activating long RNA (35S RNA) of a CaMV (Park et al. 2001). Fourthly, Gene VI disables an organism’s defense systems and make plants and other organisms susceptible to a bacterial pathogen (Love et al. 2012).

RNA silencing is a mechanism to suppress gene expression (Bartel, 2004). RNA silencing is an antiviral defense mechanism in both plants and animals, but most viral organisms evolved with genes such as Gene VI, to shut down RNA silencing (Dunoyer & Voinnet, 2006).  Hence, Gene VI raises some ethical and biosafety concerns, which include but not limited to aberrant gene expression in GMO crops and interferes with the organism’s defense mechanism against pathogens.  Apparently, it has been shown that viral proteins disables gene silencing and enhances pathogen infection in plant and animal (Latham and Wilson 2008). Perhaps, the discovery sheds light into the dark holes of GMOs technologies, and probably, a better risk-benefit assessments on GMO will be forthcoming.

Gene VI precedes the 35S RNA: Below.

Reference

Bartel P (2004)  MicroRNAs: Genomics, Biogenesis, Mechanism, and Function. Cell: 116, 281-   297.

Dunoyer P, and  O Voinnet (2006) The complex interplay between plant viruses and host RNA-silencing pathways. Curr Opinion in Plant Biology 8: 415–423.

Haas G, Azevedo J, Moissiard G, Geldreich A, Himber C, Bureau M, et al. (2008) Nuclear import of CaMV P6 is required for infection and suppression of the RNA silencing factorDRB4. EMBO J 27: 2102-12.

Latham, J & Wilson, A. (2013).  Regulators Discover a Hidden Viral Gene in Commercial GMO Crops. Retrieved from http://independentsciencenews.org/commentaries/regulators-discover-a-hidden-viral-gene-in-commercial-gmo-crops/.

Love AJ , C Geri, J Laird, C Carr, BW Yun, GJ Loake et al (2012) Cauliflower mosaic virusProtein P6 Inhibits Signaling Responses to Salicylic Acid and Regulates InnateImmunity. PLoS One. 7(10): e47535.

Podevin N and  du Jardin P (2012) Possible consequences of the overlap between the CaMV 35S promoter regions in plant transformation vectors used and the viral gene VI in transgenic plants. GM Crops and Food 3: 1-5.

Séralini, G-E., E. Clair, R. Mesnage, S. Gress, N. Defarge, M. Malatesta, D. Hennequin, J. Spiroux de Vendômois. 2012. Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize. Food Chem. Toxicol. Retrieved from http://www.ncbi.nlm nih.gov/pubmed/ 22999595