Plant Selection

Actinomycin D is an antineoplastic antibiotic from Streptomyces species that inhibits cell proliferation by acting as a cytotoxic inducer of apoptosis against tumor cells, binding to DNA and inhibiting RNA polymerase activity. Actinomycin is also used in plant tissue culture to inhibit plant growth through tissue deformation where it also acts as an RNA-synthesis inhibitor. Along with its fluorescent derivative, 7aminoactinomycinD (7-AAD), Actinomycin is used to stain GC-rich regions of DNA for microscopy and flow cytometry applications.

Bialaphos is a tripeptide antibiotic that is used in transformation experiments of many species of plants that make use of the bar gene for selection. In corn, it is more effective than glufosinate. In wheat, bialaphos was the most reliable selection criteria used to identify bar transformed plants.

Once introduced into a nonresistant plant cell, bialaphos is hydrolyzed and converted to phosphinothricin through the phosphinothricin acetyl transferase enzyme. Phosphinothricin is toxic within plants, causing ammonia to build up, which inhibits glutamine synthetase.

This broad-spectrum herbicide also has effectiveness against gram-negative and gram-positive bacteria, as well as certain fungal plant pathogens.

Chlorsulfuron is a sulfonylurea herbicide of broad-leaf plants that inhibits biosynthetic pathways of amino acids. Being a water soluble herbicide, chlorsulfuron has been studied to understand soil biodegradation rates and investigate new measuring techniques in order to prevent hazardous herbicide accumulation. It has also been used to examine cross-resistance and resistance inheritance in a variety of plants such as Sisymbrium orientale.

Chlorsulfuron specifically blocks biosynthesis of the amino acids valine and isoleucine, by inhibiting acetolactate synthase. This enzyme is the first enzyme that is specific to the synthesis of branched chain amino acids. Chlorsufluron is a noncompetitive enzyme that binds to the allosteric site and is specific to the enzyme itself and equally well to the enzyme-substrate complex.

Dicamba is benzoic acid derivative that is used as an herbicide of broad-leaf plants. It has specifically been used for plant selection and studying herbicide resistance. Dicamba is a synthetic form of the hormone auxin, a plant growth hormone. By impersonating auxin, dicamba promotes unregulated cell growth which will exhaust a plants resources and ultimately result in cell death.

Imazapyr is imidazolinone family herbicide that has been used to research herbicidal resistances and biochemical pathways in an array of plants. This compound has been shown to uncompetitively inhibit acetolactate synthase (ALS) which catalyzes the production of the amino acids valine, leucine and isoleucine. Loss of these specific amino acids depletes physiologically important proteins and enzymes, eventually resulting in cell death.

Phosphinothricin is a broad-spectrum herbicide that acts as a competitive inhibitor of glutamine synthetase.

Glutamine synthetase plays an important role in plant nitrogen metabolism. Its actions lead to the formation of glutamine; however, when inhibited by phosphinothricin, a rapid accumulation of ammonia along with reduction in glutamine occurs within plants.

This herbicide makes an ideal agent for the selection of transformed plants. Plant resistance to phosphinothricin is conferred through the bar gene, and due to the fast degradation of phosphinothricin in soil and in water, it presents a low risk for environmental contamination.