Expression and stability of amplified genes encoding 5-enolpyruvylshikimate-3-phosphate synthase in glyphosate-tolerant tobacco cells |
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Authors: | Yunxia Wang James D. Jones Stephen C. Weller Peter B. Goldsbrough |
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Affiliation: | (1) Department of Horticulture, Purdue University, 47907 West Lafayette, IN, USA;(2) Present address: Agronomy Department, University of Illinois, 1102 S. Goodwin Avenue, 61801 Urbana, IL, USA |
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Abstract: | Two distinct cDNAs for 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) were obtained from a glyphosate-tolerant tobacco cell line. The cDNAs were 89% identical and the predicted sequences of the mature proteins were greater than 83% identical with EPSPS proteins from other plants. Tobacco EPSPS proteins were more similar to those from tomato and petunia than Arabidopsis. One cDNA clone, EPSPS-1, represented a gene that was amplified in glyphosate-tolerant cells, while the gene for EPSPS-2 was unaltered in these cells. Consequently, EPSPS-1 mRNA was more abundant in tolerant than unselected cells, whereas EPSPS-2 mRNA was at relatively constant levels in these cell lines. Exposure of unselected cells and tobacco leaves to glyphosate produced a transient increase in EPSPS mRNA. However, glyphosate-tolerant cells containing amplified copies of EPSPS genes did not show a similar response following exposure to glyphosate. A significant proportion of the EPSPS gene amplification was maintained when tolerant cells were grown in the absence of glyphosate for eight months. Plants regenerated from these cells also contained amplified EPSPS genes. |
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Keywords: | tobacco 5-enolpyruvylshikimate-3-phosphate synthase cDNA clone gene expression gene amplification glyphosate cell culture tolerance |
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