Copy number of the papaya papain gene by Southern blot.
Figure Southern blot analysis for the copy number of papain gene in papaya genome. Two
hybridizing bands were detected in the lanes corresponding to EcoRI- (A) or HindIII- (B) digested
DNA DNA of four different papaya cultivars. No hybridizing band was obtained in the
EcoRI-digested DNA of maize and soybean. Lanes 1–4 correspond to Huannong NO.1, Huihuang,
Huiyou and Meizhonghong, Lane 5 corresponds to maize, Lane 6 corresponds to soybean.
Application of real-time quantitative PCR detection of transgenic papayas
Processed papaya products were purchased to evaluate the application of the established
real-time PCR methods in this study. 10 ng DNAs extracted from papaya samples were used as
template in one PCR reaction. The content of GM papaya, expressed as a percentage of weight,
was then calculated by dividing the measured copy number of the CP gene by the copy number of
the papain gene and multiplying this number by 100. Processed papaya products with GM papaya
concentrations of papaya catsup A, papaya catsup B, papaya catsup C, papaya preserve A, papaya
preserve B, papaya preserve C, papaya juice A, papaya juice B, papaya juice C, gave calculated
results of 0.0, 82.7, 91.3, 95.4, 95.0, 0.0, 84.5, 86.0, 0.0%, respectively (data not shown).
Real-time quantitative PCR detection of transgenic papayas could be applied to test the content of
GM papaya in the processed papaya products.
2