Crop Biotech Update

Scientists Compare Herbicide Resistance of Transgenic and Mutant Arabidopsis

April 4, 2012

CSR1 gene from Arabidopsis codes for the enzyme called acetolactate synthase (AHAS), which speeds up the first step in the production of branched amino acids. AHAS can be blocked by herbicides such as imazapyr and other imidazolinone herbicides. However, a substitution mutation in csr1-2 (Ser-653-Asn) causes selective resistance to imidazolinone herbicides. To confirm that AHAS is the primary target of herbicide imazapyr and that mutation does not cause changes in other physical characteristics, Jaimie Schnell from Agriculture and Agri-Food Canada and colleagues conducted a study. They created a lethal null mutant (csr1-7) by T-DNA insertion into the CSR1 gene which was complemented with a randomly-inserted 35S/CSR1-2/NOS transgene in a subsequent genetic transformation event.

The researchers compared the csr1-2 substitution mutant with the transgenic lines and discovered that all were resistant to the herbicide, though the transgenic lines exhibited higher levels of resistance and greater biomass build up with application of imazapyr. Results of the microarray analysis showed few variations in the RNA molecules.

Based on the findings, the genetic transformation did not cause any changes in the genetic expression of physical characteristics of the plants. The mutant and the transgenic lines are highly similar except for their levels of resistance.

Read the abstract at