Transcriptional analysis of nucleolar dominance in polyploid plants: Biased expression/silencing of progenitor rRNA genes is developmentally regulated in Brassica
AUTOR(ES)
Chen, Z. Jeffrey
FONTE
The National Academy of Sciences of the USA
RESUMO
Nucleolar dominance is an epigenetic phenomenon that describes the formation of nucleoli around rRNA genes inherited from only one parent in the progeny of an interspecific hybrid. Despite numerous cytogenetic studies, little is known about nucleolar dominance at the level of rRNA gene expression in plants. We used S1 nuclease protection and primer extension assays to define nucleolar dominance at a molecular level in the plant genus Brassica. rRNA transcription start sites were mapped in three diploids and in three allotetraploids (amphidiploids) and one allohexaploid species derived from these diploid progenitors. rRNA transcripts of only one progenitor were detected in vegetative tissues of each polyploid. Dominance was independent of maternal effect, ploidy, or rRNA gene dosage. Natural and newly synthesized amphidiploids yielded the same results, arguing against substantial evolutionary effects. The hypothesis that nucleolar dominance in plants is correlated with physical characteristics of rRNA gene intergenic spacers is not supported in Brassica. Furthermore, in Brassica napus, rRNA genes silenced in vegetative tissues were found to be expressed in all floral organs, including sepals and petals, arguing against the hypothesis that passage through meiosis is needed to reactivate suppressed genes. Instead, the transition of inflorescence to floral meristem appears to be a developmental stage when silenced genes can be derepressed.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=20389Documentos Relacionados
- Restricted chromosomal silencing in nucleolar dominance
- Natural variation in nucleolar dominance reveals the relationship between nucleolus organizer chromatin topology and rRNA gene transcription in Arabidopsis
- Yeast snR30 is a small nucleolar RNA required for 18S rRNA synthesis.
- Transcriptional analysis of the 16s rRNA gene in Rickettsia prowazekii.
- The Dominance of Alleles Controlling Self-Incompatibility in Brassica Pollen Is Regulated at the RNA Level