The distribution of repetitive DNAs along chromosomes is one of the crucial elements for understanding the organization and the evolution of plant genomes. Using a modified genomic in situ hybridization （GISH） proce...The distribution of repetitive DNAs along chromosomes is one of the crucial elements for understanding the organization and the evolution of plant genomes. Using a modified genomic in situ hybridization （GISH） procedure, fluorescence in situ hybridization （FISH） with genomic DNA to their own chromosomes （called self-genomic in situ hybridization, self-GISH） was carried out in six selected plant species with different genome size and amount of repetitive DNA. Nonuniform distribution of the fluorescent labeled probe DNA was observed on the chromosomes of all the species that were tested. The signal patterns varied among species and were related to the genome size. The chromosomes of the small Arabidopsis genome were labeled almost only in the pericentromeric regions and the nucleolus organizer regions （NORs）. The signals in the relatively small genomes, rice, sorghum, and Brassica oleracea var. capitata L., were dispersed along the chromosome lengths, with a predominant distribution in the pericentromeric or proximal regions and some heterochromatic arms. All chromosomes of the large genomes, maize and barley, were densely labeled with strongly labeled regions and weakly labeled or unlabeled regions being arranged alternatively throughout the lengths. In addition, enhanced signal bands were shown in all pericentromeres and the NORs in B. oleracea var. capitata, and in all pericentromeric regions and certain intercalary sites in barley. The enhanced signal band pattern in barley was found consistent with the N-banding pattern of this species. The GISH with self-genomic DNA was compared with FISH with Cot-1 DNA in rice, and their signal patterns are found to be basically consistent. Our results showed that the self-GISH signals actually reflected the hybridization of genomic repetitive DNAs to the chromosomes, thus the self-GISH technique would be useful for revealing the distribution of the regions where repetitive DNAs concentrate along chromosomes and some chromatin differentiation associated with repetitive DNAs in plants.展开更多
Recent deep sequencing surveys of mammalian genomes have unexpectedly revealed pervasive and complex transcription and identified tens of thousands of RNA transcripts that do not code for proteins. These non-coding RN...Recent deep sequencing surveys of mammalian genomes have unexpectedly revealed pervasive and complex transcription and identified tens of thousands of RNA transcripts that do not code for proteins. These non-coding RNAs(nc RNAs) highlight the central role of RNA in gene regulation. nc RNAs are arbitrarily divided into two main groups: The first includes small RNAs, such as mi RNAs, pi RNAs, and endogenous si RNAs, that usually range from 20 to 30 nt, while the second group includes long non-coding RNAs(lnc RNAs), which are typically more than 200 nt in length. These nc RNAs were initially thought to merely regulate gene expression at the post-transcriptional level, but recent studies have indicated that nc RNAs, especially lnc RNAs, are extensively associated with diverse chromatin remodeling complexes and target them to specific genomic loci to alter DNA methylation or histone status. These findings suggest an emerging theme of nc RNAs in epigenetic regulation. In this review, we discuss the wide spectrum of nc RNAs in the regulation of DNA methylation and chromatin state, as well as the key questions that needs to be investigated and acknowledging the elegant design of these intriguing macromolecules.展开更多
基金This work was supported by the National Natural Sciences Foundation of China (No. 39870423).
文摘The distribution of repetitive DNAs along chromosomes is one of the crucial elements for understanding the organization and the evolution of plant genomes. Using a modified genomic in situ hybridization （GISH） procedure, fluorescence in situ hybridization （FISH） with genomic DNA to their own chromosomes （called self-genomic in situ hybridization, self-GISH） was carried out in six selected plant species with different genome size and amount of repetitive DNA. Nonuniform distribution of the fluorescent labeled probe DNA was observed on the chromosomes of all the species that were tested. The signal patterns varied among species and were related to the genome size. The chromosomes of the small Arabidopsis genome were labeled almost only in the pericentromeric regions and the nucleolus organizer regions （NORs）. The signals in the relatively small genomes, rice, sorghum, and Brassica oleracea var. capitata L., were dispersed along the chromosome lengths, with a predominant distribution in the pericentromeric or proximal regions and some heterochromatic arms. All chromosomes of the large genomes, maize and barley, were densely labeled with strongly labeled regions and weakly labeled or unlabeled regions being arranged alternatively throughout the lengths. In addition, enhanced signal bands were shown in all pericentromeres and the NORs in B. oleracea var. capitata, and in all pericentromeric regions and certain intercalary sites in barley. The enhanced signal band pattern in barley was found consistent with the N-banding pattern of this species. The GISH with self-genomic DNA was compared with FISH with Cot-1 DNA in rice, and their signal patterns are found to be basically consistent. Our results showed that the self-GISH signals actually reflected the hybridization of genomic repetitive DNAs to the chromosomes, thus the self-GISH technique would be useful for revealing the distribution of the regions where repetitive DNAs concentrate along chromosomes and some chromatin differentiation associated with repetitive DNAs in plants.
文摘Recent deep sequencing surveys of mammalian genomes have unexpectedly revealed pervasive and complex transcription and identified tens of thousands of RNA transcripts that do not code for proteins. These non-coding RNAs(nc RNAs) highlight the central role of RNA in gene regulation. nc RNAs are arbitrarily divided into two main groups: The first includes small RNAs, such as mi RNAs, pi RNAs, and endogenous si RNAs, that usually range from 20 to 30 nt, while the second group includes long non-coding RNAs(lnc RNAs), which are typically more than 200 nt in length. These nc RNAs were initially thought to merely regulate gene expression at the post-transcriptional level, but recent studies have indicated that nc RNAs, especially lnc RNAs, are extensively associated with diverse chromatin remodeling complexes and target them to specific genomic loci to alter DNA methylation or histone status. These findings suggest an emerging theme of nc RNAs in epigenetic regulation. In this review, we discuss the wide spectrum of nc RNAs in the regulation of DNA methylation and chromatin state, as well as the key questions that needs to be investigated and acknowledging the elegant design of these intriguing macromolecules.
