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author:("gounon, rpmi")
1.  Genome Sequences of Populus tremula Chloroplast and Mitochondrion: Implications for Holistic Poplar Breeding 
PLoS ONE  2016;11(1):e0147209.
Complete Populus genome sequences are available for the nucleus (P. trichocarpa; section Tacamahaca) and for chloroplasts (seven species), but not for mitochondria. Here, we provide the complete genome sequences of the chloroplast and the mitochondrion for the clones P. tremula W52 and P. tremula x P. alba 717-1B4 (section Populus). The organization of the chloroplast genomes of both Populus clones is described. A phylogenetic tree constructed from all available complete chloroplast DNA sequences of Populus was not congruent with the assignment of the related species to different Populus sections. In total, 3,024 variable nucleotide positions were identified among all compared Populus chloroplast DNA sequences. The 5-prime part of the LSC from trnH to atpA showed the highest frequency of variations. The variable positions included 163 positions with SNPs allowing for differentiating the two clones with P. tremula chloroplast genomes (W52, 717-1B4) from the other seven Populus individuals. These potential P. tremula-specific SNPs were displayed as a whole-plastome barcode on the P. tremula W52 chloroplast DNA sequence. Three of these SNPs and one InDel in the trnH-psbA linker were successfully validated by Sanger sequencing in an extended set of Populus individuals. The complete mitochondrial genome sequence of P. tremula is the first in the family of Salicaceae. The mitochondrial genomes of the two clones are 783,442 bp (W52) and 783,513 bp (717-1B4) in size, structurally very similar and organized as single circles. DNA sequence regions with high similarity to the W52 chloroplast sequence account for about 2% of the W52 mitochondrial genome. The mean SNP frequency was found to be nearly six fold higher in the chloroplast than in the mitochondrial genome when comparing 717-1B4 with W52. The availability of the genomic information of all three DNA-containing cell organelles will allow a holistic approach in poplar molecular breeding in the future.
PMCID: PMC4723046  PMID: 26800039
2.  In plants, decapping prevents RDR6-dependent production of small interfering RNAs from endogenous mRNAs 
Nucleic Acids Research  2015;43(5):2902-2913.
Cytoplasmic degradation of endogenous RNAs is an integral part of RNA quality control (RQC) and often relies on the removal of the 5′ cap structure and their subsequent 5′ to 3′ degradation in cytoplasmic processing (P-)bodies. In parallel, many eukaryotes degrade exogenous and selected endogenous RNAs through post-transcriptional gene silencing (PTGS). In plants, PTGS depends on small interfering (si)RNAs produced after the conversion of single-stranded RNAs to double-stranded RNAs by the cellular RNA-dependent RNA polymerase 6 (RDR6) in cytoplasmic siRNA-bodies. PTGS and RQC compete for transgene-derived RNAs, but it is unknown whether this competition also occurs for endogenous transcripts. We show that the lethality of decapping mutants is suppressed by impairing RDR6 activity. We establish that upon decapping impairment hundreds of endogenous mRNAs give rise to a new class of rqc-siRNAs, that over-accumulate when RQC processes are impaired, a subset of which depending on RDR6 for their production. We observe that P- and siRNA-bodies often are dynamically juxtaposed, potentially allowing for cross-talk of the two machineries. Our results suggest that the decapping of endogenous RNA limits their entry into the PTGS pathway. We anticipate that the rqc-siRNAs identified in decapping mutants represent a subset of a larger ensemble of endogenous siRNAs.
PMCID: PMC4357720  PMID: 25694514
3.  Whole genome resequencing in tomato reveals variation associated with introgression and breeding events 
BMC Genomics  2013;14(1):791.
One of the goals of genomics is to identify the genetic loci responsible for variation in phenotypic traits. The completion of the tomato genome sequence and recent advances in DNA sequencing technology allow for in-depth characterization of genetic variation present in the tomato genome. Like many self-pollinated crops, cultivated tomato accessions show a low molecular but high phenotypic diversity. Here we describe the whole-genome resequencing of eight accessions (four cherry-type and four large fruited lines) chosen to represent a large range of intra-specific variability and the identification and annotation of novel polymorphisms.
The eight genomes were sequenced using the GAII Illumina platform. Comparison of the sequences with the reference genome yielded more than 4 million single nucleotide polymorphisms (SNPs). This number varied from 80,000 to 1.5 million according to the accessions. Almost 128,000 InDels were detected. The distribution of SNPs and InDels across and within chromosomes was highly heterogeneous revealing introgressions from wild species and the mosaic structure of the genomes of the cherry tomato accessions. In-depth annotation of the polymorphisms identified more than 16,000 unique non-synonymous SNPs. In addition 1,686 putative copy-number variations (CNVs) were identified.
This study represents the first whole genome resequencing experiment in cultivated tomato. Substantial genetic differences exist between the sequenced tomato accessions and the reference sequence. The heterogeneous distribution of the polymorphisms may be related to introgressions that occurred during domestication or breeding. The annotated SNPs, InDels and CNVs identified in this resequencing study will serve as useful genetic tools, and as candidate polymorphisms in the search for phenotype-altering DNA variations.
Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-14-791) contains supplementary material, which is available to authorized users.
PMCID: PMC4046683  PMID: 24228636
Tomato; Genome; Sequence; Single nucleotide polymorphism; Introgression
4.  Genome-Wide Association Mapping in Tomato (Solanum lycopersicum) Is Possible Using Genome Admixture of Solanum lycopersicum var. cerasiforme 
G3: Genes|Genomes|Genetics  2012;2(8):853-864.
Genome-wide association mapping is an efficient way to identify quantitative trait loci controlling the variation of phenotypes, but the approach suffers severe limitations when one is studying inbred crops like cultivated tomato (Solanum lycopersicum). Such crops exhibit low rates of molecular polymorphism and high linkage disequilibrium, which reduces mapping resolution. The cherry type tomato (S. lycopersicum var. cerasiforme) genome has been described as an admixture between the cultivated tomato and its wild ancestor, S. pimpinellifolium. We have thus taken advantage of the properties of this admixture to improve the resolution of association mapping in tomato. As a proof of concept, we sequenced 81 DNA fragments distributed on chromosome 2 at different distances in a core collection of 90 tomato accessions, including mostly cherry type tomato accessions. The 81 Sequence Tag Sites revealed 352 SNPs and indels. Molecular diversity was greatest for S. pimpinellifolium accessions, intermediate for S. l. cerasiforme accessions, and lowest for the cultivated group. We assessed the structure of molecular polymorphism and the extent of linkage disequilibrium over genetic and physical distances. Linkage disequilibrium decreased under r2 = 0.3 within 1 cM, and minimal estimated value (r2 = 0.13) was reached within 20 kb over the physical regions studied. Associations between polymorphisms and fruit weight, locule number, and soluble solid content were detected. Several candidate genes and quantitative trait loci previously identified were validated and new associations detected. This study shows the advantages of using a collection of S. l. cerasiforme accessions to overcome the low resolution of association mapping in tomato.
PMCID: PMC3411241  PMID: 22908034
tomato (Solanum lycopersicum); admixture; association mapping; linkage disequilibrium
5.  Patterns of sequence polymorphism in the fleshless berry locus in cultivated and wild Vitis vinifera accessions 
BMC Plant Biology  2010;10:284.
Unlike in tomato, little is known about the genetic and molecular control of fleshy fruit development of perennial fruit trees like grapevine (Vitis vinifera L.). Here we present the study of the sequence polymorphism in a 1 Mb grapevine genome region at the top of chromosome 18 carrying the fleshless berry mutation (flb) in order, first to identify SNP markers closely linked to the gene and second to search for possible signatures of domestication.
In total, 62 regions (17 SSR, 3 SNP, 1 CAPS and 41 re-sequenced gene fragments) were scanned for polymorphism along a 3.4 Mb interval (85,127-3,506,060 bp) at the top of the chromosome 18, in both V. vinifera cv. Chardonnay and a genotype carrying the flb mutation, V. vinifera cv. Ugni Blanc mutant. A nearly complete homozygosity in Ugni Blanc (wild and mutant forms) and an expected high level of heterozygosity in Chardonnay were revealed. Experiments using qPCR and BAC FISH confirmed the observed homozygosity. Under the assumption that flb could be one of the genes involved into the domestication syndrome of grapevine, we sequenced 69 gene fragments, spread over the flb region, representing 48,874 bp in a highly diverse set of cultivated and wild V. vinifera genotypes, to identify possible signatures of domestication in the cultivated V. vinifera compartment. We identified eight gene fragments presenting a significant deviation from neutrality of the Tajima's D parameter in the cultivated pool. One of these also showed higher nucleotide diversity in the wild compartments than in the cultivated compartments. In addition, SNPs significantly associated to berry weight variation were identified in the flb region.
We observed the occurrence of a large homozygous region in a non-repetitive region of the grapevine otherwise highly-heterozygous genome and propose a hypothesis for its formation. We demonstrated the feasibility to apply BAC FISH on the very small grapevine chromosomes and provided a specific probe for the identification of chromosome 18 on a cytogenetic map. We evidenced genes showing putative signatures of selection and SNPs significantly associated with berry weight variation in the flb region. In addition, we provided to the community 554 SNPs at the top of chromosome 18 for the development of a genotyping chip for future fine mapping of the flb gene in a F2 population when available.
PMCID: PMC3022909  PMID: 21176183

Results 1-5 (5)