Chromatin reorganization accompanying cellular dedifferentiation is associated with modifications of histone H3, redistribution of HP1, and activation of E2F-target genes.
The remarkable regeneration capacity of plant cells is based on their capability to dedifferentiate. We recently reported that cellular dedifferentiation proceeds through two distinct phases, each accompanied by chromatin decondensation: acquisition of competence for fate switch followed by a signal-dependent reentry into S phase. The purpose of this study was to (1) characterize changes in chromatin factors associated with chromatin decondensation, and (2) study the relationship between chromatin decondensation and transcriptional activation of pRb/E2F-regulated genes. We show that plant cells competent for fate switch display a disruption of nucleolar domain appearance associated with condensation of 18S ribosomal DNA, as well as modifications of histone H3 and redistribution of heterochromatin protein 1 (HP1). We further show that the pRb/E2F-target genes RNR2 and PCNA are condensed and silent in differentiated leaf cells but become decondensed, although not yet activated, as cells acquire competence for fate switch; transcriptional activation becomes evident during progression into S phase, concomitantly with pRb phosphorylation. We propose that chromatin reorganization is central for reversion of the differentiation process leading to resetting of the gene expression program and activation of silent genes.
Williams
Leor
L
Department of Plant Sciences, The Weizmann Institute of Science, Rehovot, Israel.
Zhao
Jing
J
Morozova
Nadya
N
Li
Yan
Y
Avivi
Yigal
Y
Grafi
Gideon
G
D018797:Cell Cycle Proteins; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000737:chemistry; D002478:Cells, Cultured; D002843:Chromatin / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D018506:Gene Expression Regulation, Plant; D018390:Gene Targeting; D017343:Genes, Plant; D049452:Green Fluorescent Proteins; D006570:Heterochromatin / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D008164:Luminescent Proteins / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology; D030821:Plants, Genetically Modified; D011523:Protoplasts / Q000166:cytology; D016196:S Phase; D014026:Nicotiana / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D006570:Heterochromatin; D006657:Histones; D008164:Luminescent Proteins; D014157:Transcription Factors; D049452:Green Fluorescent Proteins