Role of 5-enoylpyruvylshikimate-3-phosphate synthase in transgenic plants
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Role of 5-Enoylpyruvylshikimate-3-Phosphate Synthase in Transgenic Plants
Introduction to 5-Enoylpyruvylshikimate-3-Phosphate Synthase (EPSPS)
5-Enoylpyruvylshikimate-3-phosphate synthase (EPSPS) is a crucial enzyme in the shikimate pathway, which is essential for the biosynthesis of aromatic amino acids in plants and microorganisms. This enzyme is the primary target of the herbicide glyphosate, making it a focal point in the development of glyphosate-tolerant transgenic plants .
Glyphosate Tolerance in Transgenic Plants
Bacterial EPSPS Genes in Transgenic Plants
Several studies have demonstrated the potential of bacterial EPSPS genes to confer glyphosate tolerance in transgenic plants. For instance, the AM79 aroA gene from a bacterial source showed the highest glyphosate tolerance when expressed in transgenic tobacco plants, resulting in higher fresh weight and survival rates under glyphosate treatment compared to other aroA genes. Similarly, a novel EPSPS gene from Proteus mirabilis was successfully used to develop glyphosate-resistant Arabidopsis thaliana, confirming its potential for creating glyphosate-tolerant crops.
Citrus EPSPS Variants
In citrus plants, a variant of EPSPS mimicking the glyphosate-resistant TIPS mutant from Eleusine indica was used to develop a highly efficient selection system for transgenic citrus. This system resulted in high transformation rates and a significant percentage of non-chimeric transgenic shoots, indicating its effectiveness as an alternative to antibiotic-based selection methods.
Thermostable EPSPS from Extremophiles
The EPSPS enzyme from Thermotoga maritima, an extremophile, exhibited remarkable thermostability and glyphosate tolerance. Transgenic Arabidopsis plants expressing this enzyme showed resistance to high concentrations of glyphosate, highlighting its potential for use in developing glyphosate-tolerant crops suitable for harsh environments.
Enhanced Plant Fitness and Auxin Content
Overexpression of EPSPS genes not only confers glyphosate tolerance but also enhances plant fitness. Transgenic Arabidopsis plants overproducing EPSPS exhibited increased fecundity and auxin content, suggesting that EPSPS overexpression may stimulate auxin biosynthesis, thereby improving plant growth and reproductive success in glyphosate-free environments.
Novel EPSPS Genes and Mutations
DNA Shuffling for Improved Glyphosate Resistance
DNA shuffling techniques have been employed to enhance the glyphosate resistance of EPSPS genes. For example, a highly glyphosate-resistant mutant of the EPSPS gene from Malus domestica was developed through multiple rounds of DNA shuffling, resulting in significant improvements in glyphosate tolerance when expressed in transgenic rice.
EPSPS from Diverse Microorganisms
EPSPS genes from various microorganisms, such as Bacillus cereus and Pantoea sp., have been identified and characterized for their glyphosate tolerance. These genes, when expressed in transgenic Arabidopsis, conferred significant glyphosate resistance, demonstrating the efficiency of using microbial EPSPS genes for developing glyphosate-tolerant plants .
Conclusion
The role of 5-enoylpyruvylshikimate-3-phosphate synthase (EPSPS) in transgenic plants is pivotal for developing glyphosate-tolerant crops. By leveraging EPSPS genes from various sources, including bacteria, extremophiles, and through genetic modifications, researchers have successfully enhanced glyphosate tolerance and overall plant fitness. These advancements not only improve weed control in agriculture but also offer insights into the broader applications of EPSPS in plant biotechnology.
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