Large-scale chromatin decondensation induced in a developmentally activated transgene locus.
The high molecular weight (HMW) glutenin-encoding genes in wheat are developmentally activated in the endosperm at about 8 days after anthesis. We have investigated the physical changes that occur in these genes in two transgenic lines containing about 20 and 50 copies each of the HMW glutenin genes together with their promoters. Using fluorescence in-situ hybridisation (FISH) and confocal imaging, we demonstrate that, in non-expressing tissue, each transgene locus consists of one or two highly condensed sites, which decondense into many foci upon activation of transcription in endosperm nuclei. Initiation of transcription can precede decondensation but not vice versa. We show that, in one of the lines, cytoplasmic transcript levels are high after onset of transcription but disappear by 14 days after anthesis, whereas small interfering RNAs, which indicate post-transcriptional gene silencing (PTGS), are detected at this stage. However, the transcript levels remain high at the transcription sites, most of the transgene copies are transcriptionally active and transcriptional activity in the nucleus ceases only with cell death at the end of endosperm development.
Wegel
Eva
E
Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Colney Lane, Norwich, NR4 7UH, UK.
Vallejos
Ruben H
RH
Christou
Paul
P
Stöger
Eva
E
Shaw
Peter
P
D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D019175:DNA Methylation; D017931:DNA Primers / Q000737:chemistry; D005434:Flow Cytometry; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D005983:Glutens / Q000235:genetics; D007091:Image Processing, Computer-Assisted; D017403:In Situ Hybridization; D017404:In Situ Hybridization, Fluorescence; D008677:Metaphase; D018613:Microscopy, Confocal; D018521:Plant Physiological Phenomena; D018517:Plant Roots / Q000378:metabolism; D030821:Plants, Genetically Modified; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D012639:Seeds / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D014170:Transformation, Genetic; D019076:Transgenes; D014908:Triticum / Q000235:genetics / Q000378:metabolism
D002843:Chromatin; D017931:DNA Primers; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012313:RNA; D005983:Glutens; D004247:DNA; C037302:glutenin