The cloning of the c2 locus (U. Wienand et al., Mol. Gen. Genet. 203:202, 1986) has enabled us to characterize molecularly the transposable element insert at the c2-m3 allele. This transposable element is not capable of activating receptors of other known transposable element systems like En (Spm), Dt, Uq, Cy, Mrh, Bg and Fcu (B. McClintock, personal communication; P Schnable, personal communication; P.A. Peterson, MNL 58:3, 1984).
Southern analysis of DNA carrying the wildtype, c2-m3 and c2-m3 revertant alleles using various c2 specific probes demonstrated that this element (here termed Mpi1) is 9kb in size and is integrated in the intron of the c2 locus. Eight kb of the Mpi1 were cloned and analyzed (attempts to clone the right side of the element were unsuccessful). The left end of the element starts with the sequence CACTA (characteristic of the CACTA-family of elements, En1, Tam1, Tam2, Tgm1; A. Pereira et al., EMBO J. 5:835, 1986; U. Bonas et al., Mol. Gen. Genet. 194:138, 1984; K. Upadhyaya et al., Mol. Gen. Genet. 199:201, 1985; L.O. Vodkin et al., Cell 34:1023, 1983) and includes many direct and indirect repeats within the first 300bp.
Transcript analysis of wildtype and c2-m3 polya+ RNA (25 days after pollination) using a 5kb and a 3kb EcoRI fragment of Mpi1 revealed a 2kb-long Mpi1 -specific mRNA hybridizing to the 3kb fragment.
The Mpi1 element is a member of a family of low repetitive elements: only 10-15 copies could be detected in the maize genome.
Ulrike Weydemann, Udo Wienand, Ulla Niesbach-Klosgen, Peter A. Peterson1
and Heinz Saedler
1Ames, Iowa, Department of Agronomy
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