Jiming Jiang

Publications (96)836.87 Total impact

• Article: Copy number variation in potato - an asexually propagated autotetraploid species.

  Marina Iovene, Tao Zhang, Qunfeng Lou, C Robin Buell, Jiming Jiang
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  ABSTRACT: Copy number variation (CNV) has been revealed as a significant contributor to the genetic variation in humans. Although CNV has been reported in several model animal and plant species, the presence of CNV and its biological impact in polyploid species has not yet been documented. We conducted a fluorescence in situ hybridization (FISH)-based CNV survey in potato, a vegetatively propagated autotetraploid species (2n=4x=48). We conducted FISH analysis using 18 randomly selected potato bacterial artificial chromosome (BAC) clones in a set of 16 potato cultivars with diverse breeding backgrounds. Six BACs (33%) with insert sizes of 137-145 kb were found to be associated with large CNV events detectable at the cytological level. We demonstrate that the large CNVs associated with two specific BACs (RH102I10 and RH83C08) were widespread among potato cultivars developed in North America and Europe. We measured the transcript abundance of four genes associated with the CNV spanned by BAC RH102I10. All four genes displayed a dosage effect in transcription. Although potato is vegetatively propagated, we observed that female gametes lacking the RH102I10-associated CNV were inferior to those with at least one copy of this CNV, indicating that the RH102I10-associated CNV can impact on the growth and development of the potato plants. Our results show that CNV is highly abundant in the potato genome and may play a significant role in genetic variation of this important food crop. This article is protected by copyright. All rights reserved.
  The Plant Journal 04/2013; · 6.16 Impact Factor
• Article: Fluorescence in situ hybridization techniques for cytogenetic and genomic analyses.

  Jason G Walling, Wenli Zhang, Jiming Jiang
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  ABSTRACT: Fluorescent in situ hybridization (FISH) is a powerful method to visualize DNA sequences in the context of the whole chromosome. Yet despite the value of FISH analysis for cytogenetic studies, there are surprisingly few labs that are able to adapt the technique for their experiments in chromosomal and genome biology. Here we present a comprehensive FISH protocol acquired from over 20 years of collective experience using different plant species. Our description uses rice as a model for performing a complete FISH procedure, but the protocol can be readily adapted for other plant species. We have provided more specialized instruction beyond routine FISH, which includes the preparation of meiotic and mitotic samples suitable for FISH analysis, procedures for direct and indirect labeling of DNA probes, and techniques for increasing signal strength using layers of antibodies.
  Methods in molecular biology (Clifton, N.J.) 01/2013; 956:13-27.
• Article: Interstitial telomeric repeats are enriched in the centromeres of chromosomes in Solanum species.

  Li He, Jun Liu, Giovana A Torres, Haiqin Zhang, Jiming Jiang, Conghua Xie
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  ABSTRACT: Interstitial telomeric repeats (ITRs) were reported in a number of animal and plant species. Most ITRs are organized as short tandem arrays and are likely evolutionary relics derived from chromosomal rearrangements and DNA repairs. However, megabase-sized ITR arrays were reported in Solanum species. Here, we report a fluorescence in situ hybridization (FISH) survey of ITRs in all representative diploid Solanum species, including potato, tomato, and eggplant. FISH revealed massive amplification of ITRs in the centromeric regions of chromosomes from the Solanum species containing the B and P genomes. A significant proportion of the ITR FISH signals was mapped within the primary constrictions of the pachytene chromosomes of Solanum pinnatisectum (B genome). In addition, some ITR sites overlapped with St49, a satellite repeat enriched in centromeric DNA sequences associated with CENH3 nucleosomes, in both A and B genome Solanum species. These results show that some ITR subfamilies have been amplified and invaded in the functional centromeres of chromosomes in Solanum species.
  Chromosome Research 12/2012; · 3.09 Impact Factor
• Source

  Available from: Jiri Macas

  Article: Repeatless and repeat-based centromeres in potato: implications for centromere evolution.

  Zhiyun Gong, Yufeng Wu, Andrea Koblízková, Giovana A Torres, Kai Wang, Marina Iovene, Pavel Neumann, Wenli Zhang, Petr Novák, C Robin Buell, Jirí Macas, Jiming Jiang
  [show abstract] [hide abstract]
  ABSTRACT: Centromeres in most higher eukaryotes are composed of long arrays of satellite repeats. By contrast, most newly formed centromeres (neocentromeres) do not contain satellite repeats and instead include DNA sequences representative of the genome. An unknown question in centromere evolution is how satellite repeat-based centromeres evolve from neocentromeres. We conducted a genome-wide characterization of sequences associated with CENH3 nucleosomes in potato (Solanum tuberosum). Five potato centromeres (Cen4, Cen6, Cen10, Cen11, and Cen12) consisted primarily of single- or low-copy DNA sequences. No satellite repeats were identified in these five centromeres. At least one transcribed gene was associated with CENH3 nucleosomes. Thus, these five centromeres structurally resemble neocentromeres. By contrast, six potato centromeres (Cen1, Cen2, Cen3, Cen5, Cen7, and Cen8) contained megabase-sized satellite repeat arrays that are unique to individual centromeres. The satellite repeat arrays likely span the entire functional cores of these six centromeres. At least four of the centromeric repeats were amplified from retrotransposon-related sequences and were not detected in Solanum species closely related to potato. The presence of two distinct types of centromeres, coupled with the boom-and-bust cycles of centromeric satellite repeats in Solanum species, suggests that repeat-based centromeres can rapidly evolve from neocentromeres by de novo amplification and insertion of satellite repeats in the CENH3 domains.
  The Plant Cell 09/2012; 24(9):3559-74. · 8.99 Impact Factor
• Article: Dynamic rearrangements and gene trafficking in nascent Yh chromosome of papaya

  Jianping Wang, Jong-Kuk Na, Qingyi Yu, Andrea Gschwend, Jennifer Han, Fanchang Zeng, Rishi Aryal, Robert VanBuren, Jan E. Murray, Wenli Zhang, [......], Ching Man Wai, Ratnesh Singh, Ming-Li Wang, Xiangjia Min, Maqsudul Alam, Deborah Charlesworth, Paul H. Moore, Jiming Jiang, Andrew H. Paterson, Ray Ming
  Proceedings of the National Academy of Sciences 08/2012; 109(34):13710. · 9.68 Impact Factor
• Source

  Available from: mendel.ugr.es

  Article: Sequencing papaya X and Yh chromosomes reveals molecular basis of incipient sex chromosome evolution

  Jianping Wang, Jong-Kuk Na, Qingyi Yu, Andrea R. Gschwend, Jennifer Han, Fanchang Zeng, Rishi Aryal, Robert VanBuren, Jan E. Murray, Wenli Zhang, [......], Ching Man Wai, Ratnesh Singh, Ming-Li Wang, Xiang Jia Min, Maqsudul Alam, Deborah Charlesworth, Paul H. Moore, Jiming Jiang, Andrew H. Paterson, Ray Ming
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  ABSTRACT: Sex determination in papaya is controlled by a recently evolved XY chromosome pair, with two slightly different Y chromosomes controlling the development of males (Y) and hermaphrodites (Yh). To study the events of early sex chromosome evolution, we sequenced the hermaphrodite-specific region of the Yh chromosome (HSY) and its X counterpart, yielding an 8.1-megabase (Mb) HSY pseudomolecule, and a 3.5-Mb sequence for the corresponding X region. The HSY is larger than the X region, mostly due to retrotransposon insertions. The papaya HSY differs from the X region by two large-scale inversions, the first of which likely caused the recombination suppression between the X and Yh chromosomes, followed by numerous additional chromosomal rearrangements. Altogether, including the X and/or HSY regions, 124 transcription units were annotated, including 50 functional pairs present in both the X and HSY. Ten HSY genes had functional homologs elsewhere in the papaya autosomal regions, suggesting movement of genes onto the HSY, whereas the X region had none. Sequence divergence between 70 transcripts shared by the X and HSY revealed two evolutionary strata in the X chromosome, corresponding to the two inversions on the HSY, the older of which evolved about 7.0 million years ago. Gene content differences between the HSY and X are greatest in the older stratum, whereas the gene content and order of the collinear regions are identical. Our findings support theoretical models of early sex chromosome evolution.
  Proceedings of the National Academy of Sciences 08/2012; 109(34):13710-13715. · 9.68 Impact Factor
• Article: Genome-wide identification of regulatory DNA elements and protein-binding footprints using signatures of open chromatin in Arabidopsis.

  Wenli Zhang, Tao Zhang, Yufeng Wu, Jiming Jiang
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  ABSTRACT: Gene expression and regulation in eukaryotes is controlled by orchestrated binding of regulatory proteins, including both activators and repressors, to promoters and other cis-regulatory DNA elements. An increasing number of plant genomes have been sequenced; however, a similar effort to the ENCODE project, which aimed to identify all functional elements in the human genome, has yet to be initiated in plants. Here we report genome-wide high-resolution mapping of DNase I hypersensitive (DH) sites in the model plant Arabidopsis thaliana. We identified 38,290 and 41,193 DH sites in leaf and flower tissues, respectively. The DH sites were depleted of bulk nucleosomes and were tightly associated with RNA polymerase II binding sites. Approximately 90% of the binding sites of two well-characterized MADS domain transcription factors, APETALA1 and SEPALLATA3, were covered by the DH sites. We demonstrate that protein binding footprints within a specific genomic region can be revealed using the DH site data sets in combination with known or putative protein binding motifs and gene expression data sets. Thus, genome-wide DH site mapping will be an important tool for systematic identification of all cis-regulatory DNA elements in plants.
  The Plant Cell 07/2012; 24(7):2719-31. · 8.99 Impact Factor
• Article: Genomic in situ hybridization reveals both auto- and allopolyploid origins of different North and Central American hexaploid potato (Solanum sect. Petota) species.

  Galina Pendinen, David M Spooner, Jiming Jiang, Tatjana Gavrilenko
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  ABSTRACT: Wild potato ( Solanum L. sect. Petota Dumort.) species contain diploids (2n = 2x = 24) to hexaploids (2n = 6x = 72). J.G. Hawkes classified all hexaploid Mexican species in series Demissa Bukasov and, according to a classic five-genome hypothesis of M. Matsubayashi in 1991, all members of series Demissa are allopolyploids. We investigated the genome composition of members of Hawkes's series Demissa with genomic in situ hybridization (GISH), using labeled DNA of their putative progenitors having diploid AA, BB, or PP genome species or with DNA of tetraploid species having AABB or AAA(a)A(a) genomes. GISH analyses support S. hougasii Correll as an allopolyploid with one AA component genome and another BB component genome. Our results also indicate that the third genome of S. hougasii is more closely related to P or a P genome-related species. Solanum demissum Lindl., in contrast, has all three chromosome sets related to the basic A genome, similar to the GISH results of polyploid species of series Acaulia Juz. Our results support a more recent taxonomic division of the Mexican hexaploid species into two groups: the allopolyploid Iopetala group containing S. hougasii, and an autopolyploid Acaulia group containing S. demissum with South American species S. acaule Bitter and S. albicans (Ochoa) Ochoa.
  Genome 05/2012; 55(6):407-15. · 1.65 Impact Factor
• Article: Construction of physical maps for the sex-specific regions of papaya sex chromosomes.

  Jong-Kuk Na, Jianping Wang, Jan E Murray, Andrea R Gschwend, Wenli Zhang, Qingyi Yu, Rafael Navajas-Pérez, F Alex Feltus, Cuixia Chen, Zdenek Kubat, Paul H Moore, Jiming Jiang, Andrew H Paterson, Ray Ming
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  ABSTRACT: Papaya is a major fruit crop in tropical and subtropical regions worldwide. It is trioecious with three sex forms: male, female, and hermaphrodite. Sex determination is controlled by a pair of nascent sex chromosomes with two slightly different Y chromosomes, Y for male and Yh for hermaphrodite. The sex chromosome genotypes are XY (male), XYh (hermaphrodite), and XX (female). The papaya hermaphrodite-specific Yh chromosome region (HSY) is pericentromeric and heterochromatic. Physical mapping of HSY and its X counterpart is essential for sequencing these regions and uncovering the early events of sex chromosome evolution and to identify the sex determination genes for crop improvement. A reiterate chromosome walking strategy was applied to construct the two physical maps with three bacterial artificial chromosome (BAC) libraries. The HSY physical map consists of 68 overlapped BACs on the minimum tiling path, and covers all four HSY-specific Knobs. One gap remained in the region of Knob 1, the only knob structure shared between HSY and X, due to the lack of HSY-specific sequences. This gap was filled on the physical map of the HSY corresponding region in the X chromosome. The X physical map consists of 44 BACs on the minimum tiling path with one gap remaining in the middle, due to the nature of highly repetitive sequences. This gap was filled on the HSY physical map. The borders of the non-recombining HSY were defined genetically by fine mapping using 1460 F2 individuals. The genetically defined HSY spanned approximately 8.5 Mb, whereas its X counterpart extended about 5.4 Mb including a 900 Kb region containing the Knob 1 shared by the HSY and X. The 8.5 Mb HSY corresponds to 4.5 Mb of its X counterpart, showing 4 Mb (89%) DNA sequence expansion. The 89% increase of DNA sequence in HSY indicates rapid expansion of the Yh chromosome after genetic recombination was suppressed 2-3 million years ago. The genetically defined borders coincide with the common BACs on the minimum tiling paths of HSY and X. The minimum tiling paths of HSY and its X counterpart are being used for sequencing these X and Yh-specific regions.
  BMC Genomics 05/2012; 13:176. · 4.07 Impact Factor
• Article: Integration of Genetic and Cytological Maps and Development of a Pachytene Chromosome-based Karyotype in Papaya

  Wenli Zhang, Ching Man Wai, Ray Ming, Qingyi Yu, Jiming Jiang
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  ABSTRACT: A significant amount of genetic and genomic resources have been developed in papaya (Carica papaya, 2n = 2 = 18 {\hbox{2n = 2}} \times { = 18} ), including genetic linkage maps consisting of nine major and three minor linkage groups. However, the 12 genetic linkage groups have not been integrated with the nine chromosomes of papaya. Bacterial artificial chromosome (BAC) clones associated with each linkage group were recently isolated. These linkage group-specific BACs were mapped to meiotic pachytene chromosomes of papaya using fluorescence in situ hybridization (FISH). The FISH mapping results integrated the 12 linkage groups into the nine papaya chromosomes. We developed a pachytene chromosome-based high resolution karyotype for the hermaphrodite plant genome of papaya cultivar SunUp. The chromosomal distribution of heterochromatin in the papaya genome is provided in the karyotype with the X chromosome representing the most euchromatic chromosome in the papaya genome. FISH mapping also revealed a significant amplification of sequences related to the 5S ribosomal RNA genes, which was detected in the male-specific region of the Y chromosome, but not in the corresponding region in the X chromosome. Keywords Carica -Chromosome map-FISH-Karyotype
  Tropical Plant Biology 04/2012; 3(3):166-170.
• Article: Stable integration of an engineered megabase repeat array into the maize genome.

  Han Zhang, Bao H Phan, Kai Wang, Barbara J Artelt, Jiming Jiang, Wayne A Parrott, R Kelly Dawe
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  ABSTRACT: Plant genome engineering as a practical matter will require stable introduction of long and complex segments of DNA sequence into plant genomes. Here we show that it is possible to synthetically engineer and introduce centromere-sized satellite repeat arrays into maize. We designed a synthetic repeat monomer of 156 bp that contains five DNA-binding motifs (LacO, TetO, Gal4, LexA, and CENPB), and extended it into tandem arrays using an overlapping PCR method similar to that commonly used in gene synthesis. The PCR products were then directly transformed into maize using biolistic transformation. We identified three resulting insertion sites (arrayed binding sites), the longest of which is at least 1100 kb. The LacI DNA-binding module is sufficient to efficiently tether YFP to the arrayed binding sites. We conclude that synthetic repeats can be delivered into plant cells by omitting passage through Escherichia coli, that they generally insert into one locus, and that great lengths may be achieved. It is anticipated that these experimental approaches will be useful for future applications in artificial chromosome design.
  The Plant Journal 01/2012; 70(2):357-65. · 6.16 Impact Factor
• Source

  Available from: Petr Novák

  Article: Repeatless and Repeat-Based Centromeres in Potato: Implications for Centromere Evolution

  Zhiyun Gong, Yufeng Wu, Andrea Koblí, Giovana A Torres, Kai Wang, Marina Iovene, Pavel Neumann, Wenli Zhang, Petr Novák, C Robin Buell, Ji Rí Macas, Jiming Jiang
  [show abstract] [hide abstract]
  ABSTRACT: Centromeres in most higher eukaryotes are composed of long arrays of satellite repeats. By contrast, most newly formed centromeres (neocentromeres) do not contain satellite repeats and instead include DNA sequences representative of the genome. An unknown question in centromere evolution is how satellite repeat-based centromeres evolve from neocentromeres. We conducted a genome-wide characterization of sequences associated with CENH3 nucleosomes in potato (Solanum tuberosum). Five potato centromeres (Cen4, Cen6, Cen10, Cen11, and Cen12) consisted primarily of single-or low-copy DNA sequences. No satellite repeats were identified in these five centromeres. At least one transcribed gene was associated with CENH3 nucleosomes. Thus, these five centromeres structurally resemble neocentromeres. By contrast, six potato centromeres (Cen1, Cen2, Cen3, Cen5, Cen7, and Cen8) contained megabase-sized satellite repeat arrays that are unique to individual centromeres. The satellite repeat arrays likely span the entire functional cores of these six centromeres. At least four of the centromeric repeats were amplified from retrotransposon-related sequences and were not detected in Solanum species closely related to potato. The presence of two distinct types of centromeres, coupled with the boom-and-bust cycles of centromeric satellite repeats in Solanum species, suggests that repeat-based centromeres can rapidly evolve from neocentromeres by de novo amplification and insertion of satellite repeats in the CENH3 domains.
  The Plant Cell 01/2012; 24:3559-3574. · 8.99 Impact Factor
• Article: High-resolution mapping of open chromatin in the rice genome.

  Wenli Zhang, Yufeng Wu, James C Schnable, Zixian Zeng, Michael Freeling, Gregory E Crawford, Jiming Jiang
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  ABSTRACT: Gene expression is controlled by the complex interaction of transcription factors binding to promoters and other regulatory DNA elements. One common characteristic of the genomic regions associated with regulatory proteins is a pronounced sensitivity to DNase I digestion. We generated genome-wide high-resolution maps of DNase I hypersensitive (DH) sites from both seedling and callus tissues of rice (Oryza sativa). Approximately 25% of the DH sites from both tissues were found in putative promoters, indicating that the vast majority of the gene regulatory elements in rice are not located in promoter regions. We found 58% more DH sites in the callus than in the seedling. For DH sites detected in both the seedling and callus, 31% displayed significantly different levels of DNase I sensitivity within the two tissues. Genes that are differentially expressed in the seedling and callus were frequently associated with DH sites in both tissues. The DNA sequences contained within the DH sites were hypomethylated, consistent with what is known about active gene regulatory elements. Interestingly, tissue-specific DH sites located in the promoters showed a higher level of DNA methylation than the average DNA methylation level of all the DH sites located in the promoters. A distinct elevation of H3K27me3 was associated with intergenic DH sites. These results suggest that epigenetic modifications play a role in the dynamic changes of the numbers and DNase I sensitivity of DH sites during development.
  Genome Research 11/2011; 22(1):151-62. · 13.61 Impact Factor
• Article: Euchromatic subdomains in rice centromeres are associated with genes and transcription.

  Yufeng Wu, Shinji Kikuchi, Huihuang Yan, Wenli Zhang, Heidi Rosenbaum, A Leonardo Iniguez, Jiming Jiang
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  ABSTRACT: The presence of the centromere-specific histone H3 variant, CENH3, defines centromeric (CEN) chromatin, but poorly understood epigenetic mechanisms determine its establishment and maintenance. CEN chromatin is embedded within pericentromeric heterochromatin in most higher eukaryotes, but, interestingly, it can show euchromatic characteristics; for example, the euchromatic histone modification mark dimethylated H3 Lys 4 (H3K4me2) is uniquely associated with animal centromeres. To examine the histone marks and chromatin properties of plant centromeres, we developed a genomic tiling array for four fully sequenced rice (Oryza sativa) centromeres and used chromatin immunoprecipitation-chip to study the patterns of four euchromatic histone modification marks: H3K4me2, trimethylated H3 Lys 4, trimethylated H3 Lys 36, and acetylated H3 Lys 4, 9. The vast majority of the four histone marks were associated with genes located in the H3 subdomains within the centromere cores. We demonstrate that H3K4me2 is not a ubiquitous component of rice CEN chromatin, and the euchromatic characteristics of rice CEN chromatin are hallmarks of the transcribed sequences embedded in the centromeric H3 subdomains. We propose that the transcribed sequences located in rice centromeres may provide a barrier preventing loading of CENH3 into the H3 subdomains. The separation of CENH3 and H3 subdomains in the centromere core may be favorable for the formation of three-dimensional centromere structure and for rice centromere function.
  The Plant Cell 11/2011; 23(11):4054-64. · 8.99 Impact Factor
• Source

  Available from: PubMed Central

  Article: Strong epigenetic similarity between maize centromeric and pericentromeric regions at the level of small RNAs, DNA methylation and H3 chromatin modifications.

  Jonathan I Gent, Yuzhu Dong, Jiming Jiang, R Kelly Dawe
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  ABSTRACT: Both kinetochore function and sister chromatid cohesion can depend upon pericentromere chromatin structure, and factors associated with heterochromatin have been proposed to have general, conserved roles in distinguishing centromeres and pericentromeres and in conferring pericentromere-intrinsic functions. We applied genome-wide sequencing approaches to quantify RNA expression, DNA methylation and histone modification distributions in maize (Zea mays), focusing on two maize chromosomes with nearly fully sequenced centromeres and pericentromeres. Aside from the presence of the Histone H3 variant common to all centromeres, Centromeric Histone H3 (CENH3), we found no RNA expression or chromatin modifications that clearly differentiate pericentromeres from either centromeres or from chromosome arms, nor did we identify an epigenetic signature that accurately predicts CENH3 location. RNA expression and chromatin modification frequencies were broadly associated with distance from centromeres, gradually peaking or dipping toward arms. When interpreted in the context of experimental data from other systems, our results suggest that centromeres may confer essential functions (such as cohesion retention) to flanking sequence regardless of the local heterochromatin profile.
  Nucleic Acids Research 11/2011; 40(4):1550-60. · 8.03 Impact Factor
• Article: Conservation and purifying selection of transcribed genes located in a rice centromere.

  Chuanzhu Fan, Jason G Walling, Jianwei Zhang, Cory D Hirsch, Jiming Jiang, Rod A Wing
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  ABSTRACT: Recombination is strongly suppressed in centromeric regions. In chromosomal regions with suppressed recombination, deleterious mutations can easily accumulate and cause degeneration of genes and genomes. Surprisingly, the centromere of chromosome8 (Cen8) of rice (Oryza sativa) contains several transcribed genes. However, it remains unclear as to what selective forces drive the evolution and existence of transcribed genes in Cen8. Sequencing of orthologous Cen8 regions from two additional Oryza species, Oryza glaberrima and Oryza brachyantha, which diverged from O. sativa 1 and 10 million years ago, respectively, revealed a set of seven transcribed Cen8 genes conserved across all three species. Chromatin immunoprecipitation analysis with the centromere-specific histone CENH3 confirmed that the sequenced orthologous regions are part of the functional centromere. All seven Cen8 genes have undergone purifying selection, representing a striking phenomenon of active gene survival within a recombination-free zone over a long evolutionary time. The coding sequences of the Cen8 genes showed sequence divergence and mutation rates that were significantly reduced from those of genes located on the chromosome arms. This suggests that Oryza has a mechanism to maintain the fidelity and functionality of Cen8 genes, even when embedded in a sea of repetitive sequences and transposable elements.
  The Plant Cell 08/2011; 23(8):2821-30. · 8.99 Impact Factor
• Source

  Available from: Luis Diambra

  Article: Genome sequence and analysis of the tuber crop potato.

  Xun Xu, Shengkai Pan, Shifeng Cheng, Bo Zhang, Desheng Mu, Peixiang Ni, Gengyun Zhang, Shuang Yang, Ruiqiang Li, Jun Wang, [......], Christian W B Bachem, Jan de Boer, Theo Borm, Bjorn Kloosterman, Herman van Eck, Erwin Datema, Bas te Lintel Hekkert, Aska Goverse, Roeland C H J van Ham, Richard G F Visser
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  ABSTRACT: Potato (Solanum tuberosum L.) is the world's most important non-grain food crop and is central to global food security. It is clonally propagated, highly heterozygous, autotetraploid, and suffers acute inbreeding depression. Here we use a homozygous doubled-monoploid potato clone to sequence and assemble 86% of the 844-megabase genome. We predict 39,031 protein-coding genes and present evidence for at least two genome duplication events indicative of a palaeopolyploid origin. As the first genome sequence of an asterid, the potato genome reveals 2,642 genes specific to this large angiosperm clade. We also sequenced a heterozygous diploid clone and show that gene presence/absence variants and other potentially deleterious mutations occur frequently and are a likely cause of inbreeding depression. Gene family expansion, tissue-specific expression and recruitment of genes to new pathways contributed to the evolution of tuber development. The potato genome sequence provides a platform for genetic improvement of this vital crop.
  Nature 07/2011; 475(7355):189-95. · 36.28 Impact Factor
• Source

  Available from: Petr Novák

  Article: Organization and evolution of subtelomeric satellite repeats in the potato genome.

  Giovana A Torres, Zhiyun Gong, Marina Iovene, Cory D Hirsch, C Robin Buell, Glenn J Bryan, Petr Novák, Jiří Macas, Jiming Jiang
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  ABSTRACT: Subtelomeric domains immediately adjacent to telomeres represent one of the most dynamic and rapidly evolving regions in eukaryotic genomes. A common feature associated with subtelomeric regions in different eukaryotes is the presence of long arrays of tandemly repeated satellite sequences. However, studies on molecular organization and evolution of subtelomeric repeats are rare. We isolated two subtelomeric repeats, CL14 and CL34, from potato (Solanum tuberosum). The CL14 and CL34 repeats are organized as independent long arrays, up to 1-3 Mb, of 182 bp and 339 bp monomers, respectively. The CL14 and CL34 repeat arrays are directly connected with the telomeric repeats at some chromosomal ends. The CL14 repeat was detected at the subtelomeric regions among highly diverged Solanum species, including tomato (Solanum lycopersicum). In contrast, CL34 was only found in potato and its closely related species. Interestingly, the CL34 repeat array was always proximal to the telomeres when both CL14 and CL34 were found at the same chromosomal end. In addition, the CL34 repeat family showed more sequence variability among monomers compared with the CL14 repeat family. We conclude that the CL34 repeat family emerged recently from the subtelomeric regions of potato chromosomes and is rapidly evolving. These results provide further evidence that subtelomeric domains are among the most dynamic regions in eukaryotic genomes.
  G3 (Bethesda, Md.). 07/2011; 1(2):85-92.
• Article: Distinct DNA methylation patterns associated with active and inactive centromeres of the maize B chromosome.

  Dal-Hoe Koo, Fangpu Han, James A Birchler, Jiming Jiang
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  ABSTRACT: Centromeres are determined by poorly understood epigenetic mechanisms. Centromeres can be activated or inactivated without changing the underlying DNA sequences. However, virtually nothing is known about the epigenetic transition of a centromere from an active to an inactive state because of the lack of examples of the same centromere exhibiting alternative forms and being distinguishable from other centromeres. The centromere of the supernumerary B chromosome of maize provides such an opportunity because its functional core can be cytologically tracked, and an inactive version of the centromere is available. We developed a DNA fiber-based technique that can be used to assess the levels of cytosine methylation associated with repetitive DNA sequences. We report that DNA sequences in the normal B centromere exhibit hypomethylation. This methylation pattern is not affected by the genetic background or structural rearrangement of the B chromosome, but is slightly changed when the B chromosome is transferred to oat as an addition chromosome. In contrast, an inactive version of this same centromere exhibits hypermethylation, indicating that the inactive centromere was modified into a different epigenetic state at the DNA level.
  Genome Research 06/2011; 21(6):908-14. · 13.61 Impact Factor
• Article: Comparative FISH mapping of Daucus species (Apiaceae family).

  Marina Iovene, Pablo F Cavagnaro, Douglas Senalik, C Robin Buell, Jiming Jiang, Philipp W Simon
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  ABSTRACT: The cytogenetic characterization of the carrot genome (Daucus carota L., 2n = 18) has been limited so far, partly because of its somatic chromosome morphology and scant of chromosome markers. Here, we integrate the carrot linkage groups with pachytene chromosomes by fluorescent in situ hybridization (FISH) mapping genetically anchored bacterial artificial chromosomes (BACs). We isolated a satellite repeat from the centromeric regions of the carrot chromosomes, which facilitated the study of the pachytene-based karyotype and demonstrated that heterochromatic domains were mainly confined to the pericentromeric regions of each chromosome. Chromosome-specific BACs were used to: (1) physically locate genetically unanchored DNA sequences, (2) reveal relationships between genetic and physical distances, and (3) address chromosome evolution in Daucus. Most carrot BACs generated distinct FISH signals in 22-chromosome Daucus species, providing evidence for syntenic chromosome segments and rearrangements among them. These results provide a foundation for further cytogenetic characterization and chromosome evolution studies in Daucus.
  Chromosome Research 05/2011; 19(4):493-506. · 3.09 Impact Factor