Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2008
Publication Date: 7/18/2008
Citation: Zhu, J., Patzoldt, W.L., Shealy, R.T., Vodkin, L.O., Clough, S.J., Tranel, P.J. 2008. Transcriptome response to glyphosate in sensitive and resistant soybean. Journal of Agricultural and Food Chemistry. 56:6355-6363.
Interpretive Summary: The majority of soybean varieties planted in the U.S. are transgenic plants that carry an added gene from a bacterium that allows the plants to be insensitive to the common herbicide, glyphosate. These transgenic plants appear to be identical to non-transgenic plants in physical appearance. To determine the degree of gene expression differences that may occur in glyphosate treated and untreated transgenic plants, we used cDNA microarrays to study expression of about 27,000 genes. We found that nearly 500 genes were changing in expression in non-transgenic plants when treated with the herbicide glyphosate. However, reflecting their dramatically reduced sensitivity to glyphosate, only 18 genes were affected by glyphosate treatment in the transgenic plants. When no treatment was applied, the number of genes changing in expression in the transgenic plant versus non-transgenic, was insignificant, being within the range of natural variation seen across plants of same cultivar. These results show that the addition of the bacterial transgene had virtually no affect on gene transcription across the soybean genome when no treatment was applied, and that in response to glyphosate herbicide, only a few genes responded in the transgenic plants.
Technical Abstract: The majority of soybeans planted in the United States are resistant to glyphosate due to introduction of a gene encoding for a glyphosate-insensitive 5-enolypyruvylshikimate-3-phosphate synthase (EPSPS). Gene expression profiling was conducted using cDNA microarrays to address questions related to potential secondary effects of glyphosate. When glyphosate-sensitive plants were treated with glyphosate, 3, 170 and 311 genes were identified as having different levels of transcripts at 1, 4, and 24 hours post treatment (hpt), respectively. Differentially expressed genes were classified into functional categories and their possible roles in response to glyphosate are briefly discussed. Gene expression profiling of resistant plants treated with glyphosate indicated that the plants were marginally affected at 1 hpt and then quickly adjusted to glyphosate treatment. Ten, four, and four genes were identified as differentially expressed at 1, 4 and 24 hpt. When gene expression profiles of developing cotyledons were compared between the near-isogenic resistant and sensitive lines, two genes were identified as significantly differentially expressed out of 27,000, which was less than the empirical fdr determined from the control experiment. Quantitative real-time reverse-transcribed PCR was conducted on selected genes and yielded results consistent with those from the microarrays. Collectively, these data indicate that there are no major transriptomic changes associated with glyphosate application in glyposate-resistant soybean, nor between untreated transgenic tissue versus untreated conventional control.