Comparability of imazapyr-resistant Arabidopsis created by transgenesis and mutagenesis
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The Arabidopsis CSR1 gene codes for the enzyme acetohydroxyacid synthase (AHAS, EC 126.96.36.199), also known as acetolactate synthase, which catalyzes the first step in branched-chain amino acid biosynthesis. It is inhibited by several classes of herbicides, including the imidazolinone herbicides, such as imazapyr; however, a substitution mutation in csr1-2 (Ser-653-Asn) confers selective resistance to the imidazolinones. The transcriptome of csr1-2 seedlings grown in the presence of imazapyr has been shown in a previous study (Manabe in Plant Cell Physiol 48:1340–1358, 2007) to be identical to that of wild-type seedlings indicating that AHAS is the sole target of imazapyr and that the mutation is not associated with pleiotropic effects detectable by transcriptome analysis. In this study, a lethal null mutant, csr1-7, created by a T-DNA insertion into the CSR1 gene was complemented with a randomly-inserted 35S/CSR1-2/NOS transgene in a subsequent genetic transformation event. A comparison of the csr1-2 substitution mutant with the transgenic lines revealed that all were resistant to imazapyr; however, the transgenic lines yielded significantly higher levels of resistance and greater biomass accumulation in the presence of imazapyr. Microarray analysis revealed few differences in their transcriptomes. The most notable was a sevenfold to tenfold elevation in the CSR1-2 transcript level. The data indicate that transgenesis did not create significant unintended pleiotropic effects on gene expression and that the mutant and transgenic lines were highly similar, except for the level of herbicide resistance.
KeywordsMutagenesis Transgenesis Transcriptome Unintended effects Acetohydroxyacid synthase Acetolactate synthase
We thank the Arabidopsis Biological Resource Center for providing seeds of csr1-2 D , csr1-7 and csr1-8 and American Cyanamid (currently BASF) for providing the imazapyr, respectively. The research was funded by the Plant Biosafety Office, Plant Products Directorate, Canadian Food Inspection Agency and Feeds Section, Animal Health and Production Division, Animal Products Directorate, Canadian Food Inspection Agency. The funders did not influence the research, data, conclusions or publication.
Conflict of interest
The authors have declared that no conflict of interests exist.
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