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Maize Transformation: From Plant Material to the Release of Genetically Modified and Edited Varieties

ABSTRACT: Over the past decades, advances in plant biotechnology have allowed the development of genetically modified maize varieties that have significantly impacted agricultural management and improved the grain yield worldwide. To date, genetically modified varieties represent 30% of the world’s maize cultivated area and incorporate traits such as herbicide, insect and disease resistance, abiotic stress tolerance, high yield, and improved nutritional quality. Maize transformation, which is a prerequisite for genetically modified maize development, is no longer a major bottleneck. Protocols using morphogenic regulators have evolved significantly towards increasing transformation frequency and genotype independence. Emerging technologies using either stable or transient expression and tissue culture-independent methods, such as direct genome editing using RNA-guided endonuclease system as an in vivo desired-target mutator, simultaneous double haploid production and editing/haploid-inducer-mediated genome editing, and pollen transformation, are expected to lead significant progress in maize biotechnology. This review summarises the significant advances in maize transformation protocols, technologies, and applications and discusses the current status, including a pipeline for trait development and regulatory issues related to current and future genetically modified and genetically edited maize varieties.

SUBMITTER: Yassitepe J

PROVIDER: S-EPMC8553389 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background: Global as well as specific expression profiles of selected rat tissues were characterized to assess the safety of genetically modified (GM) maize MON810 containing the insecticidal protein Cry1Ab. Gene expression was evaluated by use of Next Generation Sequencing (NGS) as well as RT-qPCR within rat intestinal tissues based on mandatory 90-day rodent feeding studies. In parallel to two 90-day feeding studies, the transcriptional response of rat tissues was assessed as another endpoint to enhance the mechanistic interpretation of GM feeding studies and/or to facilitate the generation of a targeted hypothesis. Rats received diets containing 33% GM maize (MON810) or near-isogenic control maize. As a site of massive exposure to ingested feed the transcriptomic response of ileal and colonic tissue was profiled via RT-qPCR arrays targeting apoptosis, DNA-damage/repair, unfolded protein response (UPR). For global RNA profiling of rat ileal tissue, we applied NGS. Results: No biological response to the GM-diet was observed in male and in female rat tissues. Transcriptome wide analysis of gene expression by RNA-seq confirmed these findings. Nevertheless, gene ontology (GO) analysis clearly associated a set of distinctly regulated transcripts with circadian rhythms. We confirmed differential expression of circadian clock genes using RT-qPCR and immunoassays for selected factors, thereby indicating physiological effects caused by the time point of sampling. Conclusion: Prediction of potential unintended effects of GM-food/feed by transcriptome based profiling of intestinal tissue presents a novel approach to complement classical toxicological testing procedures. Including the detection of alterations in signaling pathways in toxicity testing procedures may enhance the confidence in outcomes of toxicological trials. In this study, no significant GM-related changes in intestinal expression profiles were found in rats fed GM-maize MON810. Relevant alterations of selected cellular pathways (apoptosis, DNA damage and repair, UPR) pointing toward intestinal toxicity of the diets were not observed. Transcriptomic profiles did not reveal perturbations of pathways associated with toxicity, underlining the study results revealed by classical OECD endpoints.

Project description:This study was conducted to follow up on apparent differences in growth, relative organ sizes, cellular stress and immune function in Atlantic salmon fed genetically modified (GM) Bt-maize compared to the non-modified parental maize line. Gene expression profiling on the distal intestinal segment and liver were performed by the cGRASP 16K salmonid cDNA microarray. Analysis of the intestinal microarray data revealed nearly 500 differentially regulated genes with a false discovery rate of zero, despite modest fold differences (average 2.4 for the down-regulated and 1.7 for the up-regulated genes). However, nine out of ten genes were found not to be significantly different when followed up by quantitative polymerase chain reaction (qPCR), but direction and magnitude of the change was generally confirmed, at least for the up-regulated genes. For the liver microarray data, statistical analyses could not be performed due to constraints in the design. qPCR revealed some differentially regulated genes in the liver, including up-regulation of gelsolin precursor, down-regulation of ferritin heavy subunit and a tendency towards down-regulation of metallothionein B. This, combined with up-regulation of anti-apoptotic protein NR13 and a tendency towards up-regulation of both ferritin heavy chain and metallothionein A and B in the distal intestine, suggests changes in cellular stress/ anti-oxidant status. This corresponds well with, and strengthens previous findings in these fish. To exclude possible confounding factors, the maize ingredients were analyzed for mycotoxins and metabolites, and the GM maize variety contain 90M-NM-<g/kg deoxynivalenol (DON), compared to levels below the detection limit in the non-GM maize. Numerous differences were also seen in the metabolite profiles of the two maize varieties, some of which seem to be connected to the mycotoxin level. The effects on salmon observed in the current and in previous studies correspond relatively well with effects of DON as reported in the literature for other production animals, but knowledge regarding effects and harmful dose levels in fish are practically non-existing, thus it is difficult to conclude whether the observed effects in the fish are caused by the DON level or by some other aspect of the GM maize ingredient.

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Maize Transformation: From Plant Material to the Release of Genetically Modified and Edited Varieties

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