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Oftentimes, researchers find themselves working not with E. coli or other bacteria, but with plant organisms that are unaffected by antibiotics. In these instances, antibiotic resistance is replaced with herbicidal resistance. While the overall process remains essentially the same, herbicide resistance falls under a different category of selectable genetic markers. | Oftentimes, researchers find themselves working not with E. coli or other bacteria, but with plant organisms that are unaffected by antibiotics. In these instances, antibiotic resistance is replaced with herbicidal resistance. While the overall process remains essentially the same, herbicide resistance falls under a different category of selectable genetic markers. | ||
One of the most common forms of herbicide resistance found in the world is glyphosate resistance. The Monsanto corporation introduced glyphosate resistance into soybeans in 1996, and provides an example of the commercial application of selectable genetic markers. Since then, Monsanto has incorporated glyphosate resistance into other plants such as canola, corn, and alfalfa. Approximately 50% of all agricultural land in the United States is now occupied by these variants, attesting to the power of selectable genetic markers<cite>Owen2010</cite>. | One of the most common forms of herbicide resistance found in the world is glyphosate resistance. Glyphosate, a common herbicide found especially in Roundup, is a competitor of the enzyme 5-enolpyruvoyl-shikimate-3-phosphate synthetase (EPSPS). The herbicide acts as a transition state analog, binding readily to EPSPS and thus inhibiting the Shikimate pathway. Monsanto introduced glyphosate resistance by first isolating a variant of EPSPS from Agrobacterium (a gram-negative bacteria) strain CP4 in the 1980s, with the unique feature of not being inhibited by glyphosate<cite>Funke2006</cite>. The Monsanto corporation introduced glyphosate resistance into soybeans in 1996, and provides an excellent example of the commercial application of selectable genetic markers. Since then, Monsanto has incorporated glyphosate resistance into other plants such as canola, corn, and alfalfa. Approximately 50% of all agricultural land in the United States is now occupied by these variants, attesting to the power of selectable genetic markers<cite>Owen2010</cite>. | ||
Selectable genetic markers for plants are not always in the form of herbicide resistance. For instance, researchers at China's Agricultural University were able to express the rstB gene in tobacco, which confers upon the plant greater tolerance to salt concentration. <i>Zhang et al.</i> was able to | Selectable genetic markers for plants are not always in the form of herbicide resistance. For instance, researchers at China's Agricultural University were able to express the rstB gene in tobacco, which confers upon the plant greater tolerance to salt concentration. <i>Zhang et al.</i> was able to achieve approximately 80% selection efficiency using salt concentrations at 170mM, proving remarkable success in using a selectable genetic marker other than herbicide resistance<cite>Zhang2008</cite>. | ||
==TO ADD: Auxotrophic== | |||
===Other=== | ===Other=== | ||
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Selectable genetic markers can also be used to investigate protein activity. Research performed at the University of Washington used GFP coupled with inteins to splice GFP into other proteins with greater than 96% efficiency. The GFP proved harmless to the intein's activity, and also allowed the researchers to analyze the effectiveness of the inteins themselves<cite>Ramsden2011</cite>. | Selectable genetic markers can also be used to investigate protein activity. Research performed at the University of Washington used GFP coupled with inteins to splice GFP into other proteins with greater than 96% efficiency. The GFP proved harmless to the intein's activity, and also allowed the researchers to analyze the effectiveness of the inteins themselves<cite>Ramsden2011</cite>. | ||
TO ADD: Neat story about GFP's discoverer | |||
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#Ramsden2011 pmid=21708017 | #Ramsden2011 pmid=21708017 | ||
//Use of inteins with GFP to introduce selectable markers into proteins. | //Use of inteins with GFP to introduce selectable markers into proteins. | ||
#Funke2006 pmid=16916934 | |||
//Molecular basis of glyphosate resistance. | |||
</biblio> | </biblio> | ||
