Studying the organization of genes encoding plant cell wall degrading enzymes in Chrysomela tremula provides insights into a leaf beetle genome.

The ability of herbivorous beetles from the superfamilies Chrysomeloidea and Curculionoidea to degrade plant cell wall polysaccharides has only recently begun to be appreciated. The presence of plant cell wall degrading enzymes (PCWDEs) in the beetle's digestive tract makes this degradation possible. Sequences encoding these beetle-derived PCWDEs were originally identified from transcriptomes and strikingly resemble those of saprophytic and phytopathogenic microorganisms, raising questions about their origin; e.g. are they insect- or microorganism-derived? To demonstrate unambiguously that the genes encoding PCWDEs found in beetle transcriptomes are indeed of insect origin, we generated a bacterial artificial chromosome library from the genome of the leaf beetle Chrysomela tremula, containing 18 432 clones with an average size of 143 kb. After hybridizing this library with probes derived from 12 C. tremula PCWDE-encoding genes and sequencing the positive clones, we demonstrated that the latter genes are encoded by the insect's genome and are surrounded by genes possessing orthologues in the genome of Tribolium castaneum as well as in three other beetle genomes. Our analyses showed that although the level of overall synteny between C. tremula and T. castaneum seems high, the degree of microsynteny between both species is relatively low, in contrast to the more closely related Colorado potato beetle.

The genome of Laccaria bicolor provides insights into mycorrhizal symbiosis.

Mycorrhizal symbioses--the union of roots and soil fungi--are universal in terrestrial ecosystems and may have been fundamental to land colonization by plants. Boreal, temperate and montane forests all depend on ectomycorrhizae. Identification of the primary factors that regulate symbiotic development and metabolic activity will therefore open the door to understanding the role of ectomycorrhizae in plant development and physiology, allowing the full ecological significance of this symbiosis to be explored. Here we report the genome sequence of the ectomycorrhizal basidiomycete Laccaria bicolor (Fig. 1) and highlight gene sets involved in rhizosphere colonization and symbiosis. This 65-megabase genome assembly contains approximately 20,000 predicted protein-encoding genes and a very large number of transposons and repeated sequences. We detected unexpected genomic features, most notably a battery of effector-type small secreted proteins (SSPs) with unknown function, several of which are only expressed in symbiotic tissues. The most highly expressed SSP accumulates in the proliferating hyphae colonizing the host root. The ectomycorrhizae-specific SSPs probably have a decisive role in the establishment of the symbiosis. The unexpected observation that the genome of L. bicolor lacks carbohydrate-active enzymes involved in degradation of plant cell walls, but maintains the ability to degrade non-plant cell wall polysaccharides, reveals the dual saprotrophic and biotrophic lifestyle of the mycorrhizal fungus that enables it to grow within both soil and living plant roots. The predicted gene inventory of the L. bicolor genome, therefore, points to previously unknown mechanisms of symbiosis operating in biotrophic mycorrhizal fungi. The availability of this genome provides an unparalleled opportunity to develop a deeper understanding of the processes by which symbionts interact with plants within their ecosystem to perform vital functions in the carbon and nitrogen cycles that are fundamental to sustainable plant productivity.

Extensive synteny conservation of holocentric chromosomes in Lepidoptera despite high rates of local genome rearrangements.

The recent assembly of the silkworm Bombyx mori genome with 432 Mb on 28 holocentric chromosomes has become a reference in the genomic analysis of the very diverse Order of Lepidoptera. We sequenced BACs from two major pests, the noctuid moths Helicoverpa armigera and Spodoptera frugiperda, corresponding to 15 regions distributed on 11 B. mori chromosomes, each BAC/region being anchored by known orthologous gene(s) to analyze syntenic relationships and genome rearrangements among the three species. Nearly 300 genes and numerous transposable elements were identified, with long interspersed nuclear elements and terminal inverted repeats the most abundant transposable element classes. There was a high degree of synteny conservation between B. mori and the two noctuid species. Conserved syntenic blocks of identified genes were very small, however, approximately 1.3 genes per block between B. mori and the two noctuid species and 2.0 genes per block between S. frugiperda and H. armigera. This corresponds to approximately two chromosome breaks per Mb DNA per My. This is a much higher evolution rate than among species of the Drosophila genus and may be related to the holocentric nature of the lepidopteran genomes. We report a large cluster of eight members of the aminopeptidase N gene family that we estimate to have been present since the Jurassic. In contrast, several clusters of cytochrome P450 genes showed multiple lineage-specific duplication events, in particular in the lepidopteran CYP9A subfamily. Our study highlights the value of the silkworm genome as a reference in lepidopteran comparative genomics.

Applying FAIR Principles to Plant Phenotypic Data Management in GnpIS.

GnpIS is a data repository for plant phenomics that stores whole field and greenhouse experimental data including environment measures. It allows long-term access to datasets following the FAIR principles: Findable, Accessible, Interoperable, and Reusable, by using a flexible and original approach. It is based on a generic and ontology driven data model and an innovative software architecture that uncouples data integration, storage, and querying. It takes advantage of international standards including the Crop Ontology, MIAPPE, and the Breeding API. GnpIS allows handling data for a wide range of species and experiment types, including multiannual perennial plants experimental network or annual plant trials with either raw data, i.e., direct measures, or computed traits. It also ensures the integration and the interoperability among phenotyping datasets and with genotyping data. This is achieved through a careful curation and annotation of the key resources conducted in close collaboration with the communities providing data. Our repository follows the Open Science data publication principles by ensuring citability of each dataset. Finally, GnpIS compliance with international standards enables its interoperability with other data repositories hence allowing data links between phenotype and other data types. GnpIS can therefore contribute to emerging international federations of information systems.

A high-quality genome sequence of Rosa chinensis to elucidate ornamental traits.

Rose is the world's most important ornamental plant, with economic, cultural and symbolic value. Roses are cultivated worldwide and sold as garden roses, cut flowers and potted plants. Roses are outbred and can have various ploidy levels. Our objectives were to develop a high-quality reference genome sequence for the genus Rosa by sequencing a doubled haploid, combining long and short reads, and anchoring to a high-density genetic map, and to study the genome structure and genetic basis of major ornamental traits. We produced a doubled haploid rose line ('HapOB') from Rosa chinensis 'Old Blush' and generated a rose genome assembly anchored to seven pseudo-chromosomes (512 Mb with N50 of 3.4 Mb and 564 contigs). The length of 512 Mb represents 90.1-96.1% of the estimated haploid genome size of rose. Of the assembly, 95% is contained in only 196 contigs. The anchoring was validated using high-density diploid and tetraploid genetic maps. We delineated hallmark chromosomal features, including the pericentromeric regions, through annotation of transposable element families and positioned centromeric repeats using fluorescent in situ hybridization. The rose genome displays extensive synteny with the Fragaria vesca genome, and we delineated only two major rearrangements. Genetic diversity was analysed using resequencing data of seven diploid and one tetraploid Rosa species selected from various sections of the genus. Combining genetic and genomic approaches, we identified potential genetic regulators of key ornamental traits, including prickle density and the number of flower petals. A rose APETALA2/TOE homologue is proposed to be the major regulator of petal number in rose. This reference sequence is an important resource for studying polyploidization, meiosis and developmental processes, as we demonstrated for flower and prickle development. It will also accelerate breeding through the development of molecular markers linked to traits, the identification of the genes underlying them and the exploitation of synteny across Rosaceae.

Mining Plant Genomic and Genetic Data Using the GnpIS Information System.

GnpIS is an information system designed to help scientists working on plants and fungi to decipher the molecular and genetic architecture of trait variations by facilitating the navigation through genetic, genomic, and phenotypic information. The purpose of the present chapter is to illustrate how users can (1) explore datasets from phenotyping experiments in order to build new datasets for studying genotype × environment interactions in traits, (2) browse into the results of other genetic analysis data such as GWAS to generate or check working hypothesis about candidate genes or to identify important alleles and germplasms for breeding programs, and (3) explore the polymorphism in specific area of the genome using InterMine, JBrowse tools embedded in the GnpIS information system.

Towards an open grapevine information system.

Viticulture, like other fields of agriculture, is currently facing important challenges that will be addressed only through sustained, dedicated and coordinated research. Although the methods used in biology have evolved tremendously in recent years and now involve the routine production of large data sets of varied nature, in many domains of study, including grapevine research, there is a need to improve the findability, accessibility, interoperability and reusability (FAIR-ness) of these data. Considering the heterogeneous nature of the data produced, the transnational nature of the scientific community and the experience gained elsewhere, we have formed an open working group, in the framework of the International Grapevine Genome Program (www.vitaceae.org), to construct a coordinated federation of information systems holding grapevine data distributed around the world, providing an integrated set of interfaces supporting advanced data modeling, rich semantic integration and the next generation of data mining tools. To achieve this goal, it will be critical to develop, implement and adopt appropriate standards for data annotation and formatting. The development of this system, the GrapeIS, linking genotypes to phenotypes, and scientific research to agronomical and oeneological data, should provide new insights into grape biology, and allow the development of new varieties to meet the challenges of biotic and abiotic stress, environmental change, and consumer demand.

Indication of linkage and genetic heterogeneity for asthma and atopy on chromosomes 8p and 12q in 107 French EGEA families.

Using the sample of 107 families with at least two asthmatic siblings, as part of the EGEA study, we have investigated linkage to asthma (or atopy) and genetic heterogeneity according to the presence/absence of atopy (or asthma) using two approaches: (1) the triangle test statistic (TTS), which considers the identical by descent (IBD) distribution among affected sib-pairs discordant for another associated phenotype (eg asthmatic sib-pairs discordant for atopy) and (2) the predivided sample test (PST), which compares the IBD distribution of marker alleles between affected sib-pairs concordant and discordant for the associated phenotype. Two regions, 8p and 12q, already reported to be linked to both asthma and atopy, were examined here. A total of 20 asthmatic sib-pairs discordant for atopy and 24 atopic pairs discordant for asthma were analyzed by both TTS and PST methods and 83 pairs with atopic asthma by PST. Some evidence for linkage was observed for two markers in the 8p23.3-p23.2 region; D8S504 for asthma with genetic heterogeneity according to the presence/absence of atopy and D8S503 for atopy with genetic heterogeneity according to the presence/absence of asthma. In the 12q14.2-q21.33 region, there was also some evidence of linkage to two markers, D12S83 and D12S95, for atopy and asthma, respectively, with genetic heterogeneity according to the presence/absence of the associated trait. Provided the small distance between the two markers on either 8p (16 cM) or 12q (21 cM), it is unclear whether one or two genetic factors are involved in either region.

Recurrent recruitment of the THAP DNA-binding domain and molecular domestication of the P-transposable element.

The recently described THAP domain motif characterizes a DNA-binding domain (DBD) that is widely conserved in human and in animals. It presents a similarity with the DBD of the P element transposase of D. melanogaster. We show here that the P Drosophila neogenes derived from P-transposable elements conserve the THAP domain. Moreover, secondary rearrangements by exon shuffling indicate the recurrent recruitment of this domain by the host genome. As P sequences and THAP genes are found together in many animal genomes, we discuss the possibility that the THAP proteins have acquired their domain as a result of recurrent molecular domestication of P-transposable elements.

Genetic algorithm-based model of evolutionary dynamics of class II transposable elements.

We propose a new conceptual framework to study the dynamics of transposable elements. Based on a genetic algorithm, our model is designed as a self-organizing system. Our results show that transposable elements could emerge from a single endonuclease gene. The DNA repair mechanisms appear to condition the emergence success of class II TEs. Antagonist selective forces acting on transposable elements and their hosts induce by their opposition differences in the sequence evolution of the functional domains and of the copies.

A simulation of P element horizontal transfer in Drosophila.

Experimental data suggest that the P transposable element has invaded the Drosophila melanogaster genome after a horizontal transfer from the phylogenetically distant species Drosophila willistoni. The differences between P element phylogeny and that of the Drosophila genus could in part be explained by horizontal transfers. In vivo experiments show that P elements are able to transpose in the genomes of other Drosophila species. This suggests that horizontal transmission of P elements could have taken place in many species of this genus. The regulation, transposition, and deleterious effects of the P element in D. melanogaster were formalized and integrated in a global model to produce a simulation program that simulates a P element invasion. The simulations show that our knowledge of the P element in D. melanogaster can explain its behavior in the Drosophila genus. The equilibrium state of the invaded population of a new species depends on its ability to repair damage caused by P element activity. If repair is efficient, the equilibrium state tends to be of the P type state, in which case the element could subsequently invade other populations of the species. Conversely, the equilibrium state is of the M' type state when the ability to repair damage is low. The invasion of the P element into other populations of this new species can then only occur by genetic drift and it is likely to be lost. The success of a P element invasion into a new species thus greatly depends on its ability to produce dysgenic crosses.

Dynamics of transposable elements in metapopulations: a model of P element invasion in Drosophila.

Work on how transposable elements are maintained and spread by virtue of their transposition processes have produced many theoretical studies of their evolutionary dynamics. But recent studies, which have experimentally identified some of these mechanisms, have not been taken into account. We present an integrated model of P transposable element regulation. It includes, at an individual level, the various mechanisms of regulation and the transposition events, that have been experimentally identified, recording specifically the chromosomal localisations of the inserted copies. It attempts to define the minimum conditions for explaining the regulation and spread of the P transposable element in Drosophila melanogaster natural populations. One test of this model is that it must explain the different population states found in the wild. A program that simulates the changes in Drosophila populations during the invasion of P elements was developed; the simulated populations were then compared to natural population data at the molecular and genetic levels. The model was validated by testing the dynamics of P element invasion in populations. It could explain the different natural population states with a recurrent invasion process. The simulations show that migration reduces the total number of copies, increases the number of defective copies, decreases P-activity and increases P-susceptibility, shifting equilibrium states from P to M'. They also show that the copies determining P-cytotype regulation spread faster by selection when located on the X chromosome. This result could account for the unexplained accumulation of P copies on the X chromosomes of some natural populations. Moreover the simulations predict a novel equilibrium state, called P', not yet characterized in natural populations but that can be found in natural population data.

Search for multifactorial disease susceptibility genes in founder populations.

The current challenge in biomedical research is to detect genetic risk factors involved in common complex diseases. The power to detect their role is generally poor in populations that have been large for a long time. It has been suggested that the power may be increased by taking advantage of the specificity of founder populations: linkage disequilibrium spanning larger regions and kinship coefficients being stronger than in large populations. A new method is proposed here, the Maximum Identity Length Contrast (MILC) which, in contrast with other existing methods, does not make the assumption of unique ancestry for the genetic risk factors. It is thus appropriate for a search for common genetic risk factors for complex diseases. Statistical properties of the method are discussed in realistic contexts.

Departure from the triangle constraints in discordant sib pairs: a test for genetic heterogeneity.

For any genetic model, Holmans showed that the proportions of affected sibs sharing 2, 1, or 0 identical-by-descent parental marker alleles are constrained to belong to a specific triangle. The triangle constraints do not hold when the sib phenotypes are determined by different models. We test the rejection of triangle constraints on affected sib pairs discordant for severity, to determine whether different models control the severe and mild forms of the disease in the simulated data. With this method we show that a locus on chromosome 5 plays a different role in the two forms of the disease.

The triangle test statistic (TTS): a test of genetic homogeneity using departure from the triangle constraints in IBD distribution among affected sib-pairs.

The proportions of affected sibs sharing 2, 1 or 0 identical by descent parental marker alleles have been shown to conform to the 'triangle constraints' (Suarez, 1978; Holmans, 1993). It has also been shown (Dudoit & Speed, 1999) that the constraints are verified provided certain assumptions hold. In this study we explore a realistic situation in which the constraints fail due to the presence of a factor in which the sibs differ, a factor on which penetrance depends. This factor may be a characteristic of the trait (severe vs. mild form), or the presence/absence of an associated trait or an environmental factor. We show that under such situations, using the triangle constraints may lead to important loss of power to detect linkage by the MLS test. We propose here an alternative approach in order to detect both linkage and heterogeneity.

Detection and modeling of disease susceptibility locus effects: how much can be learned from contrast of populations?

We report the results of our analyses of the GAW11 Problem 2 data set, using information from three different populations. In the first part of the paper, we used classical population genetic tests to compare affected individuals from the different populations, stratifying on the environmental factors. Thanks to existing linkage disequilibrium in one population, we found one of the disease susceptibility loci. In the second part of the paper, we used the marker association segregation chi 2 method to model the role of this disease susceptibility locus in the different populations and draw some inferences regarding the model used at that locus to generate the data.