Saturation mutagenesis of the octopine synthase enhancer: correlation of mutant phenotypes with binding of a nuclear protein factor

摘要: Abstract A 16-base-pair palindrome from the Agrobacterium tumefaciens octopine synthase gene functions as a constitutive enhancer in plant protoplasts. Degenerate oligonucleotide mutagenesis provided single base substitutions at every position element and number of multiple substitutions. The effects these changes were determined transient expression assays with tobacco maize majority double had little effect on activity enhancer, but nearly all mutants more than two low to essentially no activity. There five positions where particular resulted 4- 10-fold loss distribution within was asymmetric. Single deletions activity, demonstrating that cannot tolerate internal spacing. We find strong correlation between mutant phenotype reduced binding protein factor, suggesting DNA-protein complex is responsible for transcriptional enhancement; functionally active form probably involves molecule. exhibit similar phenotypes protoplasts both maize, implying conservation interactions ocs sequence monocotyledonous dicotyledonous plants.