Verification and applicability of endogenous reference genes for quantifying GM rice by digital PCR

To standardize the rice-specific quantification methods, the criteria of six genes of rice (gos9, PLD, SPS, RBE4, ppi-PPF and oriazain) were compared and evaluated by ddPCR. The results revealed that SPS, RBE4 and ppi-PPF were single copy genes per haploid genome and species specificity and stable among different rice cultivars, by employing Lectin gene of soybean as internal reference gene. The established ddPCR systems were precise and reliable with an absolute LOQ of 10-20 copies/reaction. Furthermore, the robustness of these three assays was verified by performing an intra-laboratory repeatability validation and the results showed that the three endogenous genes of rice could be quantitated repeatedly and precisely above the LOQ. These ddPCR methods can reliably quantified the GM content even if the content was low to 0.1%, which were much more reliable than the results from real-time PCR using the same primers and probes.