RNA-seq analysis of unintended effects in transgenic wheat overexpressing the transcription factor GmDREB1

The engineering of plants with enhanced tolerance to abiotic stresses typically involves complex multigene networks and may therefore have a greater potential to introduce unintended effects than the genetic modification for simple monogenic traits. For this reason, it is essential to study the unintended effects in transgenic plants engineered for stress tolerance. We selected drought-and salt-tolerant transgenic wheat overexpressing the transcription factor, GmDREB1, to investigate unintended pleiotropic effects using RNA-seq analysis. We compared the transcriptome alteration of transgenic plants with that of wild-type plants subjected to salt stress as a control. We found that GmDREB1 overexpression had a minimal impact on gene expression under normal conditions.GmDREB1 overexpression resulted in transcriptional reprogramming of the salt response,but many of the genes with differential expression are known to mitigate salt stress and contribute incrementally to the enhanced stress tolerance of transgenic wheat. GmDREB1 overexpression did not activate unintended gene networks with respect to gene expression in the roots of transgenic wheat. This work is important for establishing a method of detecting unintended effects of genetic engineering and the safety of such traits with the development of marketable transgenic crops in the near future.

Metabolic profiling of DREB-overexpressing transgenic wheat seeds by liquid chromatographymass spectrometry

DREBs are transcription factors that regulate abiotic stress tolerance in plants.Previously,we reported that wheat transgenic lines overexpressing Gm DREB1 showed increased tolerance to drought and salt stress.However,the molecular basis of increased tolerance is still poorly understood,and whether the overexpression of DREB will cause unexpected effects is also of concern.We performed seed metabolic profiling of the genetically modified(GM)wheat T349 and three non-GM cultivars with LC-MS to identify the metabolic basis of stress tolerance and to assess the unexpected effects of exogenous gene insertion.Although we did not note the appearance of novel metabolites or the disappearance of existing metabolites,overexpression of the transcription factor Gm DREB1 in T349 wheat influenced metabolite levels in seeds.Increased levels of stress tolerance-associated metabolites were found in the stress-sensitive non-transgenic acceptor counterpart J19,while metabolites associated with cell membrane structure and stability accumulated in T349.Among these metabolites in T349,most showed levels similar to those in the non-GM wheats.Overexpression of Gm DREB1 in T349 may cause a shift in its metabolic profile leading to down-regulation of several energy-consuming processes to favor increased yield under stress conditions,which is a reasonable expectation of breeders while creating the GM wheat and Gm DREB1 overexpression did not cause unexpected effects in T349 seeds.These results may be helpful for GM crop research and risk assessment.