Mutant ALS genes

A, a transgenic rice plant (To) transformed with the mutant ALS gene... 

Puhlmann M, Brown CK, Gnant M, Huang J, et al. 2000. Vaccinia as a vector for tumor directed gene therapy Biodistribution of a thymidine kinase-deleted mutant. Cancer Gene Ther. 7 66-73. 

In practical terms, the Ser264 to Gly mutation causing triazine resistance reduces plant productivity and yield. This has two agronomic implications first, triazine-resistant weeds carrying this mutation are less competitive (often referred in the literature as reduced fitness) on a per plant basis as compared to their susceptible counterparts, and second, triazine-resistant rapeseed cultivars with Hie mutant psbA gene are less productive than near isogenic, susceptible cultivars (Forcella, 1987 Beversdorf et al, 1988 Hart and Stemler, 1990 Hall et al, 1996). 

Doetschman, T., Gregg, R G., Maeda, N., Hooper, M. L., Melton, D. W., Thompson, S., et al. (1987) Targetted correction of a mutant HPRT gene in mouse embryonic stem cells. Nature 330, 576-578. 

In addition to a role in symbiosis, the presence of the VLCFA may also be important for the life of the symbiont in the soil. Recently, it was shown that a mutant in genes encoding for the fatty acyl transferases that are in the five gene VLCFA cassette of R. leguminosarum biovar viciae 3841 also fail to incorporate VLCFA into their LA and they are also less resistance to desiccation, impaired in biofilm formation, and in motility (Vanderlinde et al., 2009). Thus, in addition to promoting rhizobial life inside the plant host, the presence of VLCFA in LPS may also be important for life of the symbiont in the soil. 

Manstcin DJ, Titus MA, De Lozanne A ct al. Gene replacement in Dictyostelium generation of myosin null mutants. EMBOJ 1989 8 923-32. 

Figure 3. Assays of tobacco transformed with a mutant tobacco ALS gene. Enzyme activity in the presence of herbicide was measured in leaves of commercial tobacco cultivars transformed with the HRA gene (plants 7-54), and in untransformed plants (WT2, WT4). Activity is expressed as a percentage of the activity measured in the absence of herbicide.

Mutations can also be incorporated into the ALS gene in order to alter the specific interactions between the enzyme and its inhibitors. Site directed mutagenesis has been used to incorporate mutations into cloned plant ALS genes based both on previously characterized mutants and on computer modeling information. These altered genes have been transformed into plants, and the transgenic plants have been tested for their sensitivity to a variety of... 

Acetolactate synthase (ALS) is the target enzyme for three unrelated classes of herbicides, the sulfonylureas, the imidazolinones, and the triazolopyrimidines. We have cloned the genes which specify acetolactate synthase from a variety of wild type plants, as well as from plants which are resistant to these herbicides. The molecular basis of herbicide resistance in these plants has been deduced by comparing the nucleotide sequences of the cloned sensitive and resistant ALS genes. By further comparing these sequences to ALS sequences obtained from herbicide-resistant yeast mutants, two patterns have become clear. First, the ALS sequences that can be mutated to cause resistance are in domains that are conserved between plants, yeast and bacteria. Second, identical molecular substitutions in ALS can confer herbicide resistance in both yeast and plants. 

In the second approach, herbicide-resistance mutations in the Arabidopsis ALS gene were studied in E. coli. To do this, wild type and mutant Arabidopsis genes were functionally expressed in E. coli, such that the plant genes complemented a branched chain amino acid auxotrophy in the bacteria (Smith et al. 1989, PNAS in press). ALS enzyme assays on extracts prepared from E. coli expressing the mutant Arabidopsis gene indicated that the mutant enzyme is resistant to sulfonylurea herbicides but is sensitive to the imidazolinone herbicide imazaquin. This selective... 

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