We want to study the transcription of transposable element Ac. We have probed mRNA from seedlings and from endosperm with probes derived from Ac. We detect a 3.5 kb band that we have seen in Ac-containing tissue only, and two smaller bands that are also found in RNA from Ac-free plants.
cDNA clones have been prepared. Those clones derived from the small bands are most probably not derived from Ac, but seem to be readthrough products of Ds insertions in active genes. cDNA clones derived from the 3.5 kb band are identical to Ac in those segments where the sequence has already been determined definitely. They differ from the Ac sequence by the absence of four introns together comprising 650 bp. The three cDNA clones span a length of about 3 kb. Approximately 500 bp from the 5'-end of the RNA have not yet been found in the form of the cDNA clone. We are presently trying to establish a full length cDNA clone.
Our experiments up to now show a single transcript which tentatively starts about 150 bp inside of Ac and ends at a position 264 bp from the other end of Ac with a polyadenylation signal. The present data indicate the presence of one long uninterrupted coding frame of 807 amino acids length and the presence of a smaller open reading frame of 102 amino acids length that is completely contained in the first one near its end terminus.
Reinhard Kunze and Peter Starlinger
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