Maize-targeted mutagenesis: A knockout resource for maize

We describe an efficient system for site-selected transposon mutagenesis in maize. A total of 43,776 F-1 plants were generated by using Robertson's Mutator(Mu) pollen parents and self-pollinated to establish a library of transposon-mutagenized seed. The frequency of new seed mutants was between 10(-4) and 10(-5) per F-1 plant. As a service to the maize community, maize-targeted mutagenesis selects insertions in genes of interest from this library by using the PCR. Pedigree, knockout, sequence, phenotype, and other information is stored in a powerful interactive database (maize-targeted mutagenesis database) that enables analysis of the entire population and the handling of knockout requests. By inhibiting Mu activity in most F-1 plants, we sought to reduce somatic insertions that may cause false positives selected from pooled tissue. By monitoring the remaining Mu activity in the F-2, however, we demonstrate that seed phenotypes depend on it, and false positives occur in lines that appear to lack it. We conclude that more than half of all mutations arising in this population are suppressed on losing Mu activity. These results have implications for epigenetic models of inbreeding and for functional genomics.