Molecular and cytogenetic characterization of a transgene locus that induces silencing and methylation of homologous promoters in trans
Summary One type of homology‐dependent gene silencing in transgenic plants involves a silencing locus that is able to transcriptionally inactivate and methylate an unlinked target locus with which it shares sequence identity in promoter regions. In a manner resembling paramutation of endogenous gene...
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Published in | The Plant journal : for cell and molecular biology Vol. 17; no. 2; pp. 131 - 140 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Oxford, UK
Blackwell Science Ltd
01.01.1999
Blackwell Science |
Subjects | |
Online Access | Get full text |
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Summary: | Summary
One type of homology‐dependent gene silencing in transgenic plants involves a silencing locus that is able to transcriptionally inactivate and methylate an unlinked target locus with which it shares sequence identity in promoter regions. In a manner resembling paramutation of endogenous genes, the target locus reactivates and loses methylation progressively over several generations after segregating away from the silencing locus, which autonomously acquires stable methylation. To investigate the origins of
trans
‐silencing ability and susceptibility, we have analyzed the structures, flanking DNA sequences and chromosomal locations of a nopaline synthase promoter silencing locus,
H2
, and a sensitive target locus,
K81
. A partially resistant target locus,
Kα
, has been characterized molecularly. The complex and scrambled
H2
locus comprises six copies of the nopaline synthase promoter, two of which are collinear with prokaryotic non‐T‐DNA sequences, and is integrated close to a region of intercalary heterochromatin. These features probably contribute collectively to the silencing ability because
H2
subclones reintroduced into random locations in the K81 genome did not frequently induce silencing. Both the
K81
and
Kα
loci have simple structures, although the former contains non‐T‐DNA prokaryotic sequences that are also present at
H2
, and they are flanked by low copy plant DNA.
H2
and
K81
might interact effectively because they are present on morphologically similar chromosomes from the T subgenome of allotetraploid tobacco. |
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Bibliography: | Permanent address: Istituto Multidisciplinario de Biología Vegetal (IMBIV), Casilla de Correo 495, 5000 Córdoba, Argentina. EMBL accession numbers H Carl‐von‐Linné‐Weg 10, D‐50829 Köln, Germany. K right . α 2 left AJ006236 AJ006235 AJ006234 81 AJ006233 Present address: Max‐Planck‐Institut für Züchtungsforschung ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2 |
ISSN: | 0960-7412 1365-313X |
DOI: | 10.1046/j.1365-313X.1999.00357.x |