Effects of Tnt1 tobacco retrotransposon insertion on target gene transcription.
The effects of Tnt1 retrotransposon insertion on nitrate reductase (NR) gene transcription have been analyzed in three NR-deficient insertional, mutants of Nicotiana tabacum. In the three mutants, named h9-Nia4, h9-Nia5 and h9-Nia6, Tnt1 was inserted into exon 3, exon 2 and exon 1 of the nia2 NR alloallelle, respectively. The mutants h9-Nia4 and h9-Nia6, which contained Tnt1 insertions that were oriented opposite to the direction of nia2 gene transcription, expressed chimaeric nia2-Tnt1 RNAs, respectively 12 kb and 10 kb long. The size observed in h9-Nia6 was close to the expected size for a full-length hybrid transcript starting and ending under the control of nia2 signals (about 9 kb). The larger transcript found in h9-Nia4 was shown to be due to a failure to splice the nia2 intron 2. The mutant h9-Nia5, which contained a Tnt1 insertion oriented in parallel with the direction of nia2 transcription expressed two truncated nia2-Tnt1 RNAs, 2 kb and 6.7 kb long. These transcripts arose from termination in the long terminal repeats (LTRs) of Tnt1. Since no full-length hybrid RNA was detected, we suggest that Tnt1 carries efficient termination signals, which are more efficiently recognized in the 3' LTR than in the 5' LTR.
Pouteau
S
S
Laboratoire de Biologie Cellulaire, INRA, Versailles, France.
Spielmann
A
A
Meyer
C
C
Grandbastien
M A
MA
Caboche
M
M
D001483:Base Sequence; D015152:Blotting, Northern; D002678:Chimera; D002874:Chromosome Mapping; D015342:DNA Probes; D004251:DNA Transposable Elements / Q000502:physiology*; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000096:biosynthesis*; D010947:Plants, Toxic; D012313:RNA / Q000032:analysis; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D014026:Nicotiana / Q000235:genetics*; D014158:Transcription, Genetic
D015342:DNA Probes; D004251:DNA Transposable Elements; D012313:RNA; D009565:Nitrate Reductases; D050901:Nitrate Reductase