In the course of analyzing Adh1 mutants which had been induced in a Robertson's mutator genetic background, we have had the good fortune to capture a maize insertional sequence (Freeling, Cheng and Alleman, Develop. Genet., in press; Strommer, Hake, Bennetzen, Taylor and Freeling, 1982, Nature 300:542-544). Our mutator lines were a gift of Don Robertson. A 13 kb BamH1 fragment containing the mutator-induced allele Adh1-S3034 was isolated from a lambda library. The cloning was done by Jeff Bennetzen at International Plant Research Institute, San Carlos, CA (Bennetzen, Swanson and Freeling, in preparation). Adh1-S3034 contains a 1.35 kb insert in an intervening sequence close to the 5' end of the gene. We call this insertional sequence Mu1 and believe it to be responsible for the induction of the unstable mutants caused by Robertson's mutator genetic background. Typical maize cultivars contain no sequences with any detectable homology to Mu1, while lines presumed to carry Robertson's mutator genetic background contain very approximately 30 dispersed, intact Mu1 elements (Bennetzen and Swanson, in preparation).
Robertson (1978, Nut. Res. 51:21-28) has recovered several recessive mutants from plants carrying mutator genetic background, as have other investigators. We think that Mu1 insertion mutants may provide a handle with which to clone these dysfunctional genes. We will distribute a Mu1 specific clone to those interested in pursuing this strategy. Please write to Michael Freeling on or after March 1, 1983.
Being realists, we know that once Mu1 is released it is out of anyone's control. Since we have not yet published on Mu1 and related sequences, we hope that those who must compete with us directly will keep in touch. In particular, the use of Mu1 as an integration module for transformation studies interests us. We would like to hear about all results using Mu1, whether interesting or not.
Figure. Restriction map of 5' end of Adh1 gene with Mu1 insert. The allele is Adh1-S3034
Michael Freeling, William C. Taylor and Jeffrey L. Bennetzen*
*International Plant Research Institute, San Carlos, CA 94070
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