Ethyl methane sulfonate (EMS) mutagenesis inArabidopsisis the most widely used mutagenesis technique. EMS has high mutagenicity and low mortality and can be used in any laboratory with a fume hood. The chemical principle of EMS mutagenesis is simple; it is based on the ability of EMS to alkylate guanine bases, which results in base mispairing. An alkylated guanine will pair with a thymine base, resulting primarily in G/C to A/T transitions, which ultimately results in an amino acid change or deletion. There are several advantages to EMS mutagenesis compared with other mutagenesis techniques available forArabidopsis. First, EMS generates a high density of nonbias irreversible mutations in the genome, which permits saturation mutagenesis without having to screen a large number of individual mutants. Second, EMS mutagenesis not only generates loss-of-function mutants, but can also generate novel mutant phenotypes, which include dominant or gain-of-function versions of proteins owing to alterations of specific amino acids. This chapter describes the use of EMS mutagenesis inArabidopsisand how mutagenized plant populations should be handled after the mutagenesis event.
