Safety evaluations of the cry1Ia1 protein found in the transgenic potato 'SpuntaG2'

Hector Quemada, Michigan State University
Kelly Zarka, Michigan State University
Walter Pett, Michigan State University
Gurling Bothma, Agricultural Research Council, Pretoria


The transgenic potato 'SpuntaG2' (Solanum tuberosum), which is resistant to potato tuber moth (Phthorimaea operculella), was subjected to protein safety evaluations including protein equivalency tests for the Cry1Ia1 protein from 'SpuntaG2' and bacterially produced Cry1Ia1, toxicity and allergenicity evaluations of Cry1Ia1 protein, and compositional equivalency of 'SpuntaG2' compared with non-transgenic 'Spunta'. Western blot analysis and biological activity assays showed molecular and functional equivalency between 'SpuntaG2'-derived Cry1Ia1 protein and bacteria-derived Cry1Ia1 protein. Comparison of the Cry1Ia1 amino acid sequence to known amino acid sequences revealed no significant homology to known toxins or known allergens. Acute toxicity studies using rodents were used to calculate an acceptable daily intake (ADI) value of 20 mg·kg-1 body weight per day. The ADI value was then used to calculate a margin of exposure (MOE) of 2,222,222, which is more than 22,000 times greater than the commonly used target MOE of 100. Digestibility and thermostability assays determined that Cry1Ia1 was fully digested within 30 s of exposure to pepsin and inactive after 3 to 4 minutes at 100°C, indicating that it would not be a potential allergen. Compositional analyses revealed no difference between 'SpuntaG2' and non-transgenic 'Spunta'. These results strongly indicate that the Cry1Ia protein and the transgenic potato 'SpuntaG2' is not a human health risk.