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Isolation and characterization of centromeric repetitive DNA sequences in Saccharum spontaneum.

ABSTRACT: Sugarcane (Saccharum hybrids spp.) is the most important sugar crop that accounts for ~75% of the world's sugar production. Recently, a whole-genome sequencing project was launched on the wild species S. spontaneum. To obtain information on the DNA composition of the repeat-enriched region of the centromere, we conducted a genome-wide analysis of the DNA sequences associated with CenH3 (a mutant of histone H3 located in eukaryote centromeres) using chromatin immunoprecipitation followed by sequencing (ChIP-seq) method. We demonstrate that the centromeres contain mainly SCEN-like single satellite repeat (Ss1) and several Ty3/gypsy retrotransposon-related repeats (Ss166, Ss51, and Ss68). Ss1 dominates in the centromeric regions and spans up to 500?kb. In contrast, the Ty3/gypsy retrotransposon-related repeats are either clustered spanning over a short range, or dispersed in the centromere regions. Interestingly, Ss1 exhibits a chromosome-specific enrichment in the wild species S. spontaneum and S. robustum, but not in the domesticated species S. officinarum and modern sugarcane cultivars. This finding suggests an autopolyploid genome identity of S. spontaneum with a high level of homology among its eight sub-genomes. We also conducted a genome-wide survey of the repetitive DNAs in S. spontaneum following a similarity-based sequence clustering strategy. These results provide insight into the composition of sugarcane genome as well as the genome assembly of S. spontaneum.

SUBMITTER: Zhang W

PROVIDER: S-EPMC5278356 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Isolation and characterization of centromeric repetitive DNA sequences in Saccharum spontaneum.

Zhang Wenpan W Zuo Sheng S Li Zhanjie Z Meng Zhuang Z Han Jinlei J Song Junqi J Pan Yong-Bao YB Wang Kai K

Scientific reports 20170130

Sugarcane (Saccharum hybrids spp.) is the most important sugar crop that accounts for ~75% of the world's sugar production. Recently, a whole-genome sequencing project was launched on the wild species S. spontaneum. To obtain information on the DNA composition of the repeat-enriched region of the centromere, we conducted a genome-wide analysis of the DNA sequences associated with CenH3 (a mutant of histone H3 located in eukaryote centromeres) using chromatin immunoprecipitation followed by seque ...[more]

PMID: 28134354

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Project description:Sugarcane (Saccharum spp. hybrids) is an economically important crop widely grown in tropical and subtropical regions for sugar and ethanol production. However, the large genome size, high ploidy level, interspecific hybridization and aneuploidy make sugarcane one of the most complex genomes and have long hampered genome research in sugarcane. Modern sugarcane cultivars are derived from interspecific hybridization between S. officinarum and S. spontaneum with 80-90% of the genome from S. officinarum and 10-20% of the genome from S. spontaneum. We constructed bacterial artificial chromosome (BAC) libraries of S. officinarum variety LA Purple (2n = 8x = 80) and S. spontaneum haploid clone AP85-441 (2n = 4x = 32), and selected and sequenced 97 BAC clones from the two Saccharum BAC libraries. A total of 5,847,280 bp sequence from S. officinarum and 5,011,570 bp from S. spontaneum were assembled and 749 gene models were annotated in these BACs. A relatively higher gene density and lower repeat content were observed in S. spontaneum BACs than in S. officinarum BACs. Comparative analysis of syntenic regions revealed a high degree of collinearity in genic regions between Saccharum and Sorghum bicolor and between S. officinarum and S. spontaneum. In the syntenic regions, S. spontaneum showed expansion relative to S. officinarum, and both S. officinarum and S. spontaneum showed expansion relative to sorghum. Among the 75 full-length LTR retrotransposons identified in the Saccharum BACs, none of them are older than 2.6 mys and no full-length LTR elements are shared between S. officinarum and S. spontaneum. In addition, divergence time estimated using a LTR junction marker and a syntenic gene shared by 3 S. officinarum and 1 S. spontaneum BACs revealed that the S. spontaneum intergenic region was distant to those from the 3 homologous regions in S. officinarum. Our results suggested that S. officinarum and S. spontaneum experienced at least two rounds of independent polyploidization in each lineage after their divergence from a common ancestor.

Project description:BackgroundSugarcane is an important crop for sugar production worldwide. The Sugars Will Eventually be Exported Transporters (SWEETs) are a group of sugar transporters recently identified in sugarcane. In Saccharum spontaneum, SsSWEET13c played a role in the sucrose transportation from the source to the sink tissues, which was found to be mainly active in the mature leaf. However, the function and regulation of SWEETs in sugarcane remain elusive despite extensive studies performed on sugar metabolism.ResultsIn this study, we showed that SsSWEET13c is a member of SWEET gene family in S. spontaneum, constituting highest circadian rhythm-dependent expression. It is a functional gene that facilitates plant root elongation and increase fresh weight of Arabidopsis thaliana, when overexpressed. Furthermore, yeast one-hybrid assays indicate that 20 potential transcription factors (TFs) could bind to the SsSWEET13c promoter in S. spontaneum. We combined transcriptome data from developmental gradient leaf with distinct times during circadian cycles and stems/leaves at different growth stages. We have uncovered that 14 out of 20 TFs exhibited positive/negative gene expression patterns relative to SsSWEET13c. In the source tissues, SsSWEET13c was mainly positively regulated by SsbHLH34, SsTFIIIA-a, SsMYR2, SsRAP2.4 and SsbHLH035, while negatively regulated by SsABS5, SsTFIIIA-b and SsERF4. During the circadian rhythm, it was noticed that SsSWEET13c was more active in the morning than in the afternoon. It was likely due to the high level of sugar accumulation at night, which was negatively regulated by SsbZIP44, and positively regulated by SsbHLH34. Furthermore, in the sink tissues, SsSWEET13c was also active for sugar accumulation, which was positively regulated by SsbZIP44, SsTFIIIA-b, SsbHLH34 and SsTFIIIA-a, and negatively regulated by SsERF4, SsHB36, SsDEL1 and SsABS5. Our results were further supported by one-to-one yeast hybridization assay which verified that 12 potential TFs could bind to the promoter of SsSWEET13c.ConclusionsA module of the regulatory network was proposed for the SsSWEET13c in the developmental gradient of leaf and circadian rhythm in S. spontaneum. These results provide a novel understanding of the function and regulation of SWEET13c during the sugar transport and biomass production in S. spontaneum.

Project description:BACKGROUND:Sucrose phosphate synthase (SPS) genes play vital roles in sucrose production across various plant species. Modern sugarcane cultivar is derived from the hybridization between the high sugar content species Saccharum officinarum and the high stress tolerance species Saccharum spontaneum, generating one of the most complex genomes among all crops. The genomics of sugarcane SPS remains under-studied despite its profound impact on sugar yield. RESULTS:In the present study, 8 and 6 gene sequences for SPS were identified from the BAC libraries of S. officinarum and S. spontaneum, respectively. Phylogenetic analysis showed that SPSD was newly evolved in the lineage of Poaceae species with recently duplicated genes emerging from the SPSA clade. Molecular evolution analysis based on Ka/Ks ratios suggested that polyploidy reduced the selection pressure of SPS genes in Saccharum species. To explore the potential gene functions, the SPS expression patterns were analyzed based on RNA-seq and proteome dataset, and the sugar content was detected using metabolomics analysis. All the SPS members presented the trend of increasing expression in the sink-source transition along the developmental gradient of leaves, suggesting that the SPSs are involved in the photosynthesis in both Saccharum species as their function in dicots. Moreover, SPSs showed the higher expression in S. spontaneum and presented expressional preference between stem (SPSA) and leaf (SPSB) tissue, speculating they might be involved in the differentia of carbohydrate metabolism in these two Saccharum species, which required further verification from experiments. CONCLUSIONS:SPSA and SPSB genes presented relatively high expression and differential expression patterns between the two Saccharum species, indicating these two SPSs are important in the formation of regulatory networks and sucrose traits in the two Saccharum species. SPSB was suggested to be a major contributor to the sugar accumulation because it presented the highest expressional level and its expression positively correlated with sugar content. The recently duplicated SPSD2 presented divergent expression levels between the two Saccharum species and the relative protein content levels were highest in stem, supporting the neofunctionalization of the SPSD subfamily in Saccharum.

Dataset Information

Isolation and characterization of centromeric repetitive DNA sequences in Saccharum spontaneum.

Publications

Isolation and characterization of centromeric repetitive DNA sequences in Saccharum spontaneum.

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