Genetic Stability and Molecular-Based Environmental Safety Assessment of Transgenic Rice Harboring the HN Gene of Chicken Newcastle Disease Virus

Based on a previously validated head-to-tail dimer vaccine model, we designed a dimeric form of the Newcastle disease virus (NDV) HN protein expressed in rice endosperm (designated as Osr2HN) and initially characterized its molecular expression profile. Previous immunization studies in chickens demonstrated that two doses (0.5 μg) or a single dose (5 μg) of Osr2HN provided complete protection against viral challenge. To facilitate its commercialization, two transgenic rice lines (HN-1 and HN-2) were propagated for three generations to systematically evaluate their molecular characteristics, genetic stability and environmental safety. Insertion site analysis, combined with PCR, qRT-PCR and western blotting, confirmed that the exogenous HN gene was stably integrated into the nuclear genome without sequence variations. The transgenic lines exhibited germination rates, growth cycles and 12 agronomic traits comparable to those of the wild-type TP309, with the exception of increased grain chalkiness in HN-2. No horizontal transfer of the HN gene to weed species was detected, and pollen viability remained unchanged. Field-based biodiversity analysis revealed no adverse effects of the HN gene on pest or weed communities. Collectively, these findings from comprehensive molecular analyses and field evaluations confirm the genetic stability, agronomic performance, and environmental safety of Osr2HN-transgenic rice, providing essential data to support its commercialization as a plant-derived vaccine platform.