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Genetically modified maize (Zea mays L.) MON810 was approved for importation into China for feed use in 2004; however, the localization data concerning exogenous insertion sequences, which confer insect resistance, have been questionable. MON810 maize plants discovered in northeastern China were used to analyze the molecular characteristics of the exogenous insertion. Using PacBio-HiFi sequencing and PCR assays, we found the insertion was located in chromosome 8, and there was a CaMV35S promoter, hsp70 intron, and insecticide gene cry1Ab, except for genome sequence insertion in the MON810 event. Importantly, the 5′ and 3′ flanking sequences were located in the region of 55869747–55879326 and 68416240–68419152 on chromosome 5, respectively. The results of this study correct previous results on the genomic localization of the insertion structure for the MON810 event. We also found a single-nucleotide polymorphism (SNP) in the hsp70 intron, which is most likely the first SNP found in a transgenic insertion sequence. PCR amplification in conjunction with Sanger sequencing, allele-specific PCR (AS-PCR), and blocker displacement amplification (BDA) assays were all effective at detecting the base variance. The integrated strategy used in this study can serve as a model for other cases when facing similar challenges involving partially characterized genetic modification events or SNPs. [ABSTRACT FROM AUTHOR]

The structure and expression of exogenous genes in transgenic crops are critical for the target traits. R7569 has the same exogenous insertion structure as the transgenic insect-resistant cotton MON531 but with a deletion in the 3′ end of the cry1Ac gene and the terminator region. Thus, in the present study, transcription, expression, and insecticidal activity assays were conducted to determine the function of the truncated cry1Ac gene. R7569 has a truncated cry1Ac gene with a length of 2554 bp encoding 881 amino acids, and the transcription termination site was mainly concentrated downstream of the truncated position and extended 160–270 bp from the truncated position using rapid amplification of cDNA ends (RACE). The transcript levels of the cry1Ac gene in R7569 were significantly higher than those of MON531 implants, except for during the boll stage. The content of the Cry1Ac protein in R7569 was higher than that of MON531 in the cotton leaf in all three periods. The corrected mortality rates of R7569 and MON531 against bollworms were 93.09% and 88.83%, respectively. The LC50 value of R7569 was 0.732 ng/g (dw), indicating a high level of resistance to bollworm. In this study, for the first time, we found a partial deletion of the target gene in commercially applied transgenic crops, and the partial deletion of the 3′ end of the cry1Ac gene retained a better transcription, expression level, and insecticidal activity, which can provide a specific case for the safety evaluation of transgenic crops. [ABSTRACT FROM AUTHOR]

Societal Impact Statement: Advancements in science and technology enable us to address the challenges of the times: hunger, malnutrition, climate change, and dwindling natural resources. One of the most significant innovations in food and agriculture is the advent of genetic engineering, which may help us address the aforementioned challenges. Millions of people could benefit from the application of genetically engineered crops in agriculture and food. However, it is vital that biosafety assessments of unintended effects are carried out to identify any potential risks to humans, the environment, or society. Summary: The study compared the extent of siRNA, transcriptomic and metabolomic changes in the leaves of four RNAi‐based genetically engineered rice lines to evaluate whether RNAi‐based genetically engineered rice that is resistant to black‐streaked dwarf virus experiences changes not seen in the non‐genetically engineered counterpart.siRNA, transcriptome, and metabolome profiling were conducted. siRNAs with different lengths and abundance were highly enriched in the transcript of rice; however, relative expression analysis of eight potential off‐target genes revealed that there was no decrease in gene expression in the RNAi‐based genetically engineered lines, meaning that no off‐target phenomena were caused as a result of siRNA derived from invert repeat sequences of rice black‐streaked dwarf virus in this study.This study identified some differentially expressed genes and differentially accumulated metabolites in the RNAi‐based genetically engineered lines; however, they were not enriched in pathways detrimental for humans, animals and the environment. Only 30 differentially expressed genes were significantly enriched in the plant hormone signal transduction pathway via a combined analysis using two‐way orthogonal partial least squares model. These genes belonging to salicylic acid, jasmonic acid, cytokinin, abscisic acid, and brassinosteroid pathway involved in pathways related to virus resistance or infection response were significantly changed.Taken together, there was no off‐target in RNAi‐based genetically engineered rice lines and may have a positive effect on virus resistance overall in this study. [ABSTRACT FROM AUTHOR]