Natural variation explains most transcriptomic changes among maize plants of MON810 and comparable non-GM varieties subjected to two N-fertilization farming practices

Abstract

The introduction of genetically modified organisms (GMO) in many countries follows strict regulations to ensure that only safety-tested products are marketed. Over the last few years, targeted approaches have been complemented by profiling methods to assess possible unintended effects of transformation. Here we used a commercial (Affymertix) microarray platform (i.e. allowing assessing the expression of approximately 1/3 of the genes of maize) to evaluate transcriptional differences between commercial MON810 GM maize and non-transgenic crops in real agricultural conditions, in a region where about 70% of the maize grown was MON810. To consider natural variation in gene expression in relation to biotech plants we took two common MON810/non-GM variety pairs as examples, and two farming practices (conventional and low-nitrogen fertilization). MON810 and comparable non-GM varieties grown in the field have very low numbers of sequences with differential expression, and their identity differs among varieties. Furthermore, we show that the differences between a given MON810 variety and the non-GM counterpart do not appear to depend to any major extent on the assayed cultural conditions, even though these differences may slightly vary between the conditions. In our study, natural variation explained most of the variability in gene expression among the samples. Up to 37.4% was dependent upon the variety (obtained by conventional breeding) and 31.9% a result of the fertilization treatment. In contrast, the MON810 GM character had a very minor effect (9.7%) on gene expression in the analyzed varieties and conditions, even though similar cryIA(b) expression levels were detected in the two MON810 varieties and nitrogen treatments. This indicates that transcriptional differences of conventionally-bred varieties and under different environmental conditions should be taken into account in safety assessment studies of GM plants.

Evaluation of Genetically Engineered Crops Using Transcriptomic, Proteomic, and Metabolomic Profiling Techniques

“…In real agricultural conditions, under two farming practices (conventional and low-nitrogen fertilization), Coll et al (2010a) found differential expression for only 0.14% of the analyzed sequences (approximately one-third of the maize genome). Analysis of the expression of a subset of sequences in a different MON810/non-GE pair indicated that varietal differences had the highest impact on gene expression patterns, followed by nitrogen availability, while the MON810 characteristic had the lowest impact.…”

Proteomic analysis of MON810 and comparable non-GM maize varieties grown in agricultural fields

“…Transcriptomics, proteomics and metabolomics analysis showed small differential transcripts/proteins/metabolites between MON810 and non-GM samples (Coll et al 2008;Manetti et al 2006;Piccioni et al 2009); and the effects of varying environmental conditions were higher than those of the transgene (Barros et al 2010;Coll et al 2010).…”

“…The differences between GM and non-GM maize (''unexpected effects'') may not be the same when different variety pairs are compared. Only a few previous works based on transcriptomics and metabolomics took into account different MON810 and near-isogenic varieties; and remarkably they showed that transcripts and metabolites mostly show altered concentrations in MON810 and non-GM samples in a variety specific manner (Coll et al 2008(Coll et al , 2010Levandi et al 2008). Although this approach has been recommended by several authors (Ruebelt et al 2006;Van Dijk et al 2009), a proteomics based research to cover this aspect is lacking.…”

Profiling of Genetically Modified Organisms Using Omics Technologies

“…In a series of articles, Coll et al reported the comparative study of different MON810 varieties with their near-isogenic counterpart [42,43]. In the first study, after in vitro culturing of the maize plantlets under highly controlled experimental conditions (to avoid changes due to environmental factors), high-density Affymetrix microarray technology was used to analyze the gene expression [42].…”

“…These results suggest that the genetic background of each variety has a great influence when assessing the substantial equivalence of GM crops. In a later study, a similar methodology was applied to assess the effect of different field environments and cultural conditions over MON810 maize varieties and their counterparts [43]. Microarray data revealed a deregulation of 0.07-0.2% of the maize transcriptome when growing the plants under low-nitrogen and control conditions.…”