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In maize, abundant pollen production and easy controlled pollination permit the direct mutagenesis of pollen to produce populations of independent mutant lines. Pollen can be treated with alkylating agents, such as ethyl methanesulfonate (EMS), to induce point mutations. The ease of applying and decontaminating this mutagen after the mutagenesis application and the advantages provided by the mutation spectra for subsequent bioinformatic analysis make EMS an attractive mutagen. We provide a maize pollen mutagenesis protocol with a list of critical supplies, a step-by-step procedure, and troubleshooting tips. Pollen is freshly collected and suspended in an emulsion of EMS and paraffin oil. The slurry of pollen, oil, and EMS is then directly placed on prepared maize silks to perform pollinations. Mutations result during embryogenesis due to replication-dependent mispairing at alkylated residues contributed by sperm nuclei. Thus, each seed bears an independent set of mutations. These progenies can be analyzed directly, as is the case in targeted mutagenesis experiments or the exploration of dominant genetic variation. Alternatively, the progenies of self-pollinated plants can be screened in the next generation to discover novel recessive mutations. In addition to the dose of EMS and contact time, the genetic background of maize can significantly influence outcomes, and some optimization of dose and contact time may be required for a genetic background and specific use case. Although we outline good practices for safe handling of EMS and waste, researchers should consult their local safety officers to ensure safe handling, decontamination, and disposal of EMS, which is toxic.
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This content will become publicly available on April 1, 2027
Uses and Opportunities for Ethyl Methanesulfonate Mutagenesis in Maize
Creating mutations in maize has provided key foundational information for our mechanistic understanding of genetics, evolution, and even the role of chromosomes as units of inheritance. Chemical mutagenesis is used in biological research to create novel genetic variation. Ethyl methanesulfonate (EMS) is an alkylating agent and a highly potent and frequently used mutagen. EMS mutagenesis can be used to identify genes based on phenotypes induced by mutagenesis (forward genetics) and to validate the functions of genes by independently creating multiple mutant alleles in known genes (reverse genetics). Due to our ability to collect huge quantities of maize pollen and to easily apply pollen to the silks of maize ears to conduct pollination and achieve hundreds of fertilization events, pollen EMS mutagenesis is uniquely facile in maize. While pollen EMS mutagenesis is commonly performed, treatment of maize seeds with EMS is also highly effective, and can be used for certain research objectives that are difficult to achieve with pollen mutagenesis, such as recovering mutant sectors. The alkylation of guanine residues by EMS primarily results in G > A or C > T transitions in the DNA, making the molecular profiling of mutations caused by EMS easy, with an extremely low false positive rate. EMS is hydrophilic, has a moderate half-life in water, and is sensitive to light and high temperatures. With appropriate precautions in research settings, EMS can be relatively safe to handle. Here, we provide an introduction to chemical mutagenesis via EMS, including some history on its use in maize and the considerations for the effective and safe design of mutagenesis experiments with EMS in maize.
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- Award ID(s):
- 2309932
- PAR ID:
- 10687261
- Publisher / Repository:
- Cold Spring Harbor Press
- Date Published:
- Journal Name:
- Cold Spring Harbor Protocols
- Volume:
- 2026
- Issue:
- 4
- ISSN:
- 1940-3402
- Page Range / eLocation ID:
- pdb.top108504
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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