Using the allyl alcohol selection technique, we have isolated a mutant in the Adh1 gene. The mutant has a null phenotype. In the pollen it reverts to wild type ADH activity at a frequency of between 10-4 and 10-1 in the presence of Ac. In the absence of Ac it is stable. The mutant differs phenotypically from another Ds-induced mutant, Adh1-Fm335, isolated by Osterman and Schwartz, which is much more unstable and quite leaky.
Restriction maps of the wild-type Adh1-F and the mutant Adh1-2F11 allele were constructed by analyzing genomic blots with an Adh1 probe isolated by Bennetzen and Freeling. The mutant allele contains a 1.3 kb insert in the Adh1 gene.
Northern blots with RNA isolated from wild-type and mutant strains were probed with the Adh1 clone. In the wild type, one band of approximately 1650 bp length is seen. In the mutant, two bands are seen. One is identical in size to the wild type band, the other band is approximately 1.3 kb larger and may be the product of cotranscription of the insert. This latter band also hybridizes to a Ds probe derived from the cloned sh-m5933 insert.
These observations show that the transposable element Ds can exist in different forms which differ at least in size. We will show below that Ds can be an internal deletion of Ac. The finding, however, of a second Bam site in the Adh insertion but not present in the 2.04 kb Ds of sh-m5933 or in Ac (see below), raises the interesting possibility that different copies of Ds may not only differ from Ac by internal deletions but also by other mutations, or even the addition of sequences not present in Ac. We have in the meantime cloned the Adh1-2F11 allele and are studying it at the DNA level. This work is in press in Mol. Gen. Genet.
H. P. Doring, M. Freeling,* S. Hake,* M. A. Johns,* R. Kunze, A. Merckelbach, F. Salamini** and P. Starlinger
*Univ. California-Berkeley, Dept. of Genetics
**Ist. Sper. Cerealicolt., Bergamo, Italy
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