Transcriptional analysis of nucleolar dominance in polyploid plants: Biased expression/silencing of progenitor rRNA genes is developmentally regulated in Brassica

被引:196
|
作者
Chen, ZJ [1 ]
Pikaard, CS [1 ]
机构
[1] WASHINGTON UNIV, DEPT BIOL, ST LOUIS, MO 63130 USA
关键词
rDNA; nucleolus; RNA polymerase I; gene silencing; epigenetic phenomena;
D O I
10.1073/pnas.94.7.3442
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Nucleolar dominance is an epigenetic phenomenon that describes the formation of nucleoli around rRNA genes inherited fl om 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 plant, 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 he derepressed.
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页码:3442 / 3447
页数:6
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