Marian R. Goldsmith

The construction of an EST database for Bombyx mori and its application

To build a foundation for the complete genome analysis of Bombyx mori, we have constructed an EST database. Because gene expression patterns deeply depend on tissues as well as developmental stages, we analyzed many cDNA libraries prepared from various tissues and different developmental stages to cover the entire set of Bombyx genes. So far, the Bombyx EST database contains 35,000 ESTs from 36 cDNA libraries, which are grouped into ≈11,000 nonredundant ESTs with the average length of 1.25 kb. The comparison with FlyBase suggests that the present EST database, SilkBase, covers >55% of all genes of Bombyx. The fraction of library-specific ESTs in each cDNA library indicates that we have not yet reached saturation, showing the validity of our strategy for constructing an EST database to cover all genes. To tackle the coming saturation problem, we have checked two methods, subtraction and normalization, to increase coverage and decrease the number of housekeeping genes, resulting in a 5–11% increase of library-specific ESTs. The identification of a number of genes and comprehensive cloning of gene families have already emerged from the SilkBase search. Direct links of SilkBase with FlyBase and WormBase provide ready identification of candidate Lepidoptera-specific genes.

The i5K Initiative: Advancing Arthropod Genomics for Knowledge, Human Health, Agriculture, and the Environment

Insects and their arthropod relatives including mites, spiders, and crustaceans play major roles in the worlds terrestrial, aquatic, and marine ecosystems. Arthropods compete with humans for food and transmit devastating diseases. They also comprise the most diverse and successful branch of metazoan evolution, with millions of extant species. Here, we describe an international effort to guide arthropod genomic efforts, from species prioritization to methodology and informatics. The 5000 arthropod genomes initiative (i5K) community met formally in 2012 to discuss a roadmap for sequencing and analyzing 5000 high-priority arthropods and is continuing this effort via pilot projects, the development of standard operating procedures, and training of students and career scientists. With university, governmental, and industry support, the i5K Consortium aspires to deliver sequences and analytical tools for each of the arthropod branches and each of the species having beneficial and negative effects on humankind.

Creating a Buzz About Insect Genomes

WHEN E. O. WILSON PROCLAIMED THAT INSECTS ARE THE “little creatures who run the world” (1), he was simply reaffi rming the long-recognized dominance of the largest class of animals on our planet. Insects constitute approximately 53% of all living species, with one group alone (the ants), accounting for almost a quarter of terrestrial animal biomass (2). These tiny creatures also exert outsized impacts on human affairs. By serving as pollinators to more than 75% of fl owering plant species (3), insects are essential to the maintenance and productivity of natural and agricultural ecosystems. But other insects consume or damage more than 25% of all agricultural, forestry, and livestock production in the United States, costing our economy more than

Single amino acid mutation in an ATP-binding cassette transporter gene causes resistance to Bt toxin Cry1Ab in the silkworm, Bombyx mori

30 billion annually (4). These losses occur despite more than 150 years of concerted efforts to prevent them. Insects and other arthropods not only affect our food supply, they also carry disease. Parasites and pathogens carried by insects and their relatives have led to more loss of human life than all wars in recorded history; even today, insect-borne diseases are a leading cause of death of children under the age of 5 (5). The annual cost of vector-borne diseases worldwide is estimated at almost

KAIKObase: An integrated silkworm genome database and data mining tool

50 billion (6). Clearly, our health and well-being depend on our ability to understand and manage arthropods of agricultural, medical, and veterinary importance. In the past decade, biomedical research has increasingly relied on information obtained from sequencing the human genome, and early genome-enabled successes have inspired a new vision of genomic medicine (7). We believe that genomics also can improve our lives by contributing to a better understanding of insect biology and transforming our ability to manage arthropods that threaten our health, food supply, and economic security. Because of the overwhelming diversity and abundance of insects, achieving these goals will require a project of grand scale. Therefore, we, the undersigned, are pleased to announce the launch of the “i5k” initiative to sequence the genomes of 5000 species of insects and other arthropods during the next 5 years (8). This project is aimed at sequencing and analyzing the genomes of all species known to be important to worldwide agriculture and food safety, medicine, and energy production; all species used as models in biology; the most abundant insects in world ecosystems; and, to achieve a deep understanding of arthropod evolution, representatives of insect relatives in every major branch of arthropod phylogeny. The i5k initiative will be broad and inclusive, seeking to involve scientists from around the world and obtain funding from academia, governments, industry, and private sources. We also aim to encourage new collaborative research by computer scientists, bioinformaticians, and biologists to overcome the challenges of handling this unprecedented volume of data and derive meaning from these genomes. GENE E. ROBINSON,* KEVIN J. HACKETT, MARY PURCELL-MIRAMONTES, SUSAN J. BROWN, JAY D. EVANS, MARIAN R. GOLDSMITH, DANIEL LAWSON, JACK OKAMURO, HUGH M. ROBERTSON, DAVID J. SCHNEIDER Department of Entomology, University of Illinois at UrbanaChampaign, Urbana, IL 61801, USA. USDA Agricultural Research Service, Beltsville, MD 20705, USA. USDA National Institute of Food and Agriculture, Washington, DC 20250, USA. Division of Biology, Kansas State University, Manhattan, KS 66506–4190, USA. Arthropod Genomics Consortium and European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SD, UK. College of the Environment and Life Sciences, University of Rhode Island, Kingston, RI 02881, USA. USDA Agricultural Research Service, Ithaca, NY 14853, USA.

The Glanville fritillary genome retains an ancient karyotype and reveals selective chromosomal fusions in Lepidoptera

Bt toxins derived from the arthropod bacterial pathogen Bacillus thuringiensis are widely used for insect control as insecticides or in transgenic crops. Bt resistance has been found in field populations of several lepidopteran pests and in laboratory strains selected with Bt toxin. Widespread planting of crops expressing Bt toxins has raised concerns about the potential increase of resistance mutations in targeted insects. By using Bombyx mori as a model, we identified a candidate gene for a recessive form of resistance to Cry1Ab toxin on chromosome 15 by positional cloning. BGIBMGA007792-93, which encodes an ATP-binding cassette transporter similar to human multidrug resistance protein 4 and orthologous to genes associated with recessive resistance to Cry1Ac in Heliothis virescens and two other lepidopteran species, was expressed in the midgut. Sequences of 10 susceptible and seven resistant silkworm strains revealed a common tyrosine insertion in an outer loop of the predicted transmembrane structure of resistant alleles. We confirmed the role of this ATP-binding cassette transporter gene in Bt resistance by converting a resistant silkworm strain into a susceptible one by using germline transformation. This study represents a direct demonstration of Bt resistance gene function in insects with the use of transgenesis.

A BAC-based integrated linkage map of the silkworm Bombyx mori

BackgroundThe silkworm, Bombyx mori, is one of the most economically important insects in many developing countries owing to its large-scale cultivation for silk production. With the development of genomic and biotechnological tools, B. mori has also become an important bioreactor for production of various recombinant proteins of biomedical interest. In 2004, two genome sequencing projects for B. mori were reported independently by Chinese and Japanese teams; however, the datasets were insufficient for building long genomic scaffolds which are essential for unambiguous annotation of the genome. Now, both the datasets have been merged and assembled through a joint collaboration between the two groups.DescriptionIntegration of the two data sets of silkworm whole-genome-shotgun sequencing by the Japanese and Chinese groups together with newly obtained fosmid- and BAC-end sequences produced the best continuity (~3.7 Mb in N50 scaffold size) among the sequenced insect genomes and provided a high degree of nucleotide coverage (88%) of all 28 chromosomes. In addition, a physical map of BAC contigs constructed by fingerprinting BAC clones and a SNP linkage map constructed using BAC-end sequences were available. In parallel, proteomic data from two-dimensional polyacrylamide gel electrophoresis in various tissues and developmental stages were compiled into a silkworm proteome database. Finally, a Bombyx trap database was constructed for documenting insertion positions and expression data of transposon insertion lines.ConclusionFor efficient usage of genome information for functional studies, genomic sequences, physical and genetic map information and EST data were compiled into KAIKObase, an integrated silkworm genome database which consists of 4 map viewers, a gene viewer, and sequence, keyword and position search systems to display results and data at the level of nucleotide sequence, gene, scaffold and chromosome. Integration of the silkworm proteome database and the Bombyx trap database with KAIKObase led to a high-grade, user-friendly, and comprehensive silkworm genome database which is now available from URL: http://sgp.dna.affrc.go.jp/KAIKObase/.

Construction of a single nucleotide polymorphism linkage map for the silkworm, Bombyx mori, based on bacterial artificial chromosome end sequences.

Previous studies have reported that chromosome synteny in Lepidoptera has been well conserved, yet the number of haploid chromosomes varies widely from 5 to 223. Here we report the genome (393 Mb) of the Glanville fritillary butterfly (Melitaea cinxia; Nymphalidae), a widely recognized model species in metapopulation biology and eco-evolutionary research, which has the putative ancestral karyotype of n=31. Using a phylogenetic analyses of Nymphalidae and of other Lepidoptera, combined with orthologue-level comparisons of chromosomes, we conclude that the ancestral lepidopteran karyotype has been n=31 for at least 140 My. We show that fusion chromosomes have retained the ancestral chromosome segments and very few rearrangements have occurred across the fusion sites. The same, shortest ancestral chromosomes have independently participated in fusion events in species with smaller karyotypes. The short chromosomes have higher rearrangement rate than long ones. These characteristics highlight distinctive features of the evolutionary dynamics of butterflies and moths.

A Genetic-Linkage Map for the Domesticated Silkworm, Bombyx-Mori, Based on Restriction-Fragment-Length-Polymorphisms

BackgroundIn 2004, draft sequences of the model lepidopteran Bombyx mori were reported using whole-genome shotgun sequencing. Because of relatively shallow genome coverage, the silkworm genome remains fragmented, hampering annotation and comparative genome studies. For a more complete genome analysis, we developed extended scaffolds combining physical maps with improved genetic maps.ResultsWe mapped 1,755 single nucleotide polymorphism (SNP) markers from bacterial artificial chromosome (BAC) end sequences onto 28 linkage groups using a recombining male backcross population, yielding an average inter-SNP distance of 0.81 cM (about 270 kilobases). We constructed 6,221 contigs by fingerprinting clones from three BAC libraries digested with different restriction enzymes, and assigned a total of 724 single copy genes to them by BLAST (basic local alignment search tool) search of the BAC end sequences and high-density BAC filter hybridization using expressed sequence tags as probes. We assigned 964 additional expressed sequence tags to linkage groups by restriction fragment length polymorphism analysis of a nonrecombining female backcross population. Altogether, 361.1 megabases of BAC contigs and singletons were integrated with a map containing 1,688 independent genes. A test of synteny using Oxford grid analysis with more than 500 silkworm genes revealed six versus 20 silkworm linkage groups containing eight or more orthologs of Apis versus Tribolium, respectively.ConclusionThe integrated map contains approximately 10% of predicted silkworm genes and has an estimated 76% genome coverage by BACs. This provides a new resource for improved assembly of whole-genome shotgun data, gene annotation and positional cloning, and will serve as a platform for comparative genomics and gene discovery in Lepidoptera and other insects.

Repression of tyrosine hydroxylase is responsible for the sex-linked chocolate mutation of the silkworm, Bombyx mori

We have developed a linkage map for the silkworm Bombyx mori based on single nucleotide polymorphisms (SNPs) between strains p50T and C108T initially found on regions corresponding to the end sequences of bacterial artificial chromosome (BAC) clones. Using 190 segregants from a backcross of a p50T female × an F1 (p50T × C108T) male, we analyzed segregation patterns of 534 SNPs between p50T and C108T, detected among 3840 PCR amplicons, each associated with a p50T BAC end sequence. This enabled us to construct a linkage map composed of 534 SNP markers spanning 1305 cM in total length distributed over the expected 28 linkage groups. Of the 534 BACs whose ends harbored the SNPs used to construct the linkage map, 89 were associated with 107 different ESTs. Since each of the SNP markers is directly linked to a specific genomic BAC clone and to whole-genome sequence data, and some of them are also linked to EST data, the SNP linkage map will be a powerful tool for investigating silkworm genome properties, mutation mapping, and map-based cloning of genes of industrial and agricultural interest.