Farmers are constantly in need of a more diversified herbicide treatment program. Though RoundUp has held the position of the world’s top selling herbicide for quite some time, scientists and farmers have been hard at work testing alternatives, such as bialaphos, to better handle the near-certainty and complication of herbicide tolerance. This natural herbicide, along with its metabolite phosphinothricin, marketed in its ammonium salt form as Liberty or Basta, appears to be gaining popularity. Scientists have been successfully producing bialaphos-resistant crop plants through current transfection technologies. The development of these new crops will offer farmers the flexibility of using bialaphos and phosphinothricin as effective alternate herbicides.
Briefly, as discussed in a 2012 product spotlight, bialaphos becomes phosphinothricin (PPT) in the plant cell, which inhibits glutamine biosynthesis unless transgenic enzymes encoded by the pat or bar genes are present in the plant to break it down. We will now begin a three-part series of blogs highlighting recently published research involving the use of this herbicide.
Recently, employing Gold Biotechnology’s bialaphos and PPT for selection, North Carolina State scientists, working under a grant from Bayer Crop Science, demonstrated improved Agrobacterium-mediated ryegrass crop transfection using heat and maltose treatment. Half a world away in Taiwan, GoldBio’s bialaphos was also chosen by a group of Nanjing University (PRC) scientists for use in research published this year reporting the creation of a bialaphos-resistant soybean line via Agrobacterium tumefaciens-mediated transfection. Finally, a group at Shimane University in Japan recently constructed new Gateway® binary vectors employing the bialaphos resistance (bar) gene for use in studying plant promoters. Their research focuses on powerful promoter:reporter analysis techniques to study tissue and cell-specific gene expression.
In the case of the Japanese research team’s work, R4L1 Ti plasmids for Agrobacterium-mediated transfection wer developed with multiple reporter genes, such as G3GFP, G3 green fluorescent protein and GUS, B-glucoronidase in addition to selectable markers like bar, which conveys bialaphos resistance. The bar gene is under the control of the constitutive nopaline synthase (nos) promoter and terminator, while the reporter genes: G3GFP, TagRFP, GUS, etc., often linked together to be polycistronic, depend upon the host promoter adjacent to the plant chromosomal insertion site for expression. Tissue-specific promoter activity can be interrogated in robust fashion using this method. In the image below, panel F shows selection on phosphinothricin ammonium, while panel J shows imaging of GFP (green) and TagRFP (red) expression in leaf tissue. The key advantage of employing binary vectors for transfection via Agrobacterium lies in the ability to generate plant lines from plants already containing separate genetic modifications, which remain homozygous in the progeny. Previous methods involved crossing promoter:reporter plants with existing lines to stack the desired modifications. This older methodology required laborious analysis of progeny to find the desired genotypes.
Future blog entries will further discuss the generation of bialaphos-resistant ryegrass achieved at North Carolina State University and the bialaphos-resistant soybean developed at Nanjing University. GoldBio is excited to be the choice of researchers seeking to further understanding of the biology of crop plants important to populations throughout the world.
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