Asian Citrus Psyllid Expression Profiles Suggest Candidatus Liberibacter Asiaticus-Mediated Alteration of Adult Nutrition and Metabolism, and of Nymphal Development and Immunity.

The Asian citrus psyllid (ACP) Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is the insect vector of the fastidious bacterium Candidatus Liberibacter asiaticus (CLas), the causal agent of citrus greening disease, or Huanglongbing (HLB). The widespread invasiveness of the psyllid vector and HLB in citrus trees worldwide has underscored the need for non-traditional approaches to manage the disease. One tenable solution is through the deployment of RNA interference technology to silence protein-protein interactions essential for ACP-mediated CLas invasion and transmission. To identify psyllid interactor-bacterial effector combinations associated with psyllid-CLas interactions, cDNA libraries were constructed from CLas-infected and CLas-free ACP adults and nymphs, and analyzed for differential expression. Library assemblies comprised 24,039,255 reads and yielded 45,976 consensus contigs. They were annotated (UniProt), classified using Gene Ontology, and subjected to in silico expression analyses using the Transcriptome Computational Workbench (TCW) (http://www.sohomoptera.org/ACPPoP/). Functional-biological pathway interpretations were carried out using the Kyoto Encyclopedia of Genes and Genomes databases. Differentially expressed contigs in adults and/or nymphs represented genes and/or metabolic/pathogenesis pathways involved in adhesion, biofilm formation, development-related, immunity, nutrition, stress, and virulence. Notably, contigs involved in gene silencing and transposon-related responses were documented in a psyllid for the first time. This is the first comparative transcriptomic analysis of ACP adults and nymphs infected and uninfected with CLas. The results provide key initial insights into host-parasite interactions involving CLas effectors that contribute to invasion-virulence, and to host nutritional exploitation and immune-related responses that appear to be essential for successful ACP-mediated circulative, propagative CLas transmission.

Comparative proteomic analysis of developing rhizomes of the ancient vascular plant Equisetum hyemale and different monocot species.

The rhizome is responsible for the invasiveness and competitiveness of many plants with great economic and agricultural impact worldwide. Besides its value as an invasive organ, the rhizome plays a role in the establishment and massive growth of forage, providing biomass for biofuel production. Despite these features, little is known about the molecular mechanisms that contribute to rhizome growth, development, and function in plants. In this work, we characterized the proteome of rhizome apical tips and elongation zones from different species using a GeLC-MS/MS (one-dimensional electrophoresis in combination with liquid chromatography coupled online with tandem mass spectrometry) spectral-counting proteomics strategy. Five rhizomatous grasses and an ancient species were compared to study the protein regulation in rhizomes. An average of 2200 rhizome proteins per species were confidently identified and quantified. Rhizome-characteristic proteins showed similar functional distributions across all species analyzed. The over-representation of proteins associated with central roles in cellular, metabolic, and developmental processes indicated accelerated metabolism in growing rhizomes. Moreover, 61 rhizome-characteristic proteins appeared to be regulated similarly among analyzed plants. In addition, 36 showed conserved regulation between rhizome apical tips and elongation zones across species. These proteins were preferentially expressed in rhizome tissues regardless of the species analyzed, making them interesting candidates for more detailed investigative studies about their roles in rhizome development.

Assessing fungal community structure from mineral surfaces in Kartchner Caverns using multiplexed 454 pyrosequencing.

Research on the distribution and structure of fungal communities in caves is lacking. Kartchner Caverns is a wet and mineralogically diverse carbonate cave located in an escarpment of Mississippian Escabrosa limestone in the Whetstone Mountains, Arizona, USA. Fungal diversity from speleothem and rock wall surfaces was examined with 454 FLX Titanium sequencing technology using the Internal Transcribed Spacer 1 as a fungal barcode marker. Fungal diversity was estimated and compared between speleothem and rock wall surfaces, and its variation with distance from the natural entrance of the cave was quantified. Effects of environmental factors and nutrient concentrations in speleothem drip water at different sample sites on fungal diversity were also examined. Sequencing revealed 2,219 fungal operational taxonomic units (OTUs) at the 95% similarity level. Speleothems supported a higher fungal richness and diversity than rock walls. However, community membership and the taxonomic distribution of fungal OTUs at the class level did not differ significantly between speleothems and rock walls. Both OTU richness and diversity decreased significantly with increasing distance from the natural cave entrance. Community membership and taxonomic distribution of fungal OTUs also differed significantly between the sampling sites closest to the entrance and those furthest away. There was no significant effect of temperature, CO2 concentration, or drip water nutrient concentration on fungal community structure on either speleothems or rock walls. Together, these results suggest that proximity to the natural entrance is a critical factor in determining fungal community structure on mineral surfaces in Kartchner Caverns.

Comparison of potato and asian citrus psyllid adult and nymph transcriptomes identified vector transcripts with potential involvement in circulative, propagative liberibacter transmission.

The potato psyllid (PoP) Bactericera cockerelli (Sulc) and Asian citrus psyllid (ACP) Diaphorina citri Kuwayama are the insect vectors of the fastidious plant pathogen, Candidatus Liberibacter solanacearum (CLso) and Ca. L. asiaticus (CLas), respectively. CLso causes Zebra chip disease of potato and vein-greening in solanaceous species, whereas, CLas causes citrus greening disease. The reliance on insecticides for vector management to reduce pathogen transmission has increased interest in alternative approaches, including RNA interference to abate expression of genes essential for psyllid-mediated Ca. Liberibacter transmission. To identify genes with significantly altered expression at different life stages and conditions of CLso/CLas infection, cDNA libraries were constructed for CLso-infected and -uninfected PoP adults and nymphal instars. Illumina sequencing produced 199,081,451 reads that were assembled into 82,224 unique transcripts. PoP and the analogous transcripts from ACP adult and nymphs reported elsewhere were annotated, organized into functional gene groups using the Gene Ontology classification system, and analyzed for differential in silico expression. Expression profiles revealed vector life stage differences and differential gene expression associated with Liberibacter infection of the psyllid host, including invasion, immune system modulation, nutrition, and development.

Allele Workbench: transcriptome pipeline and interactive graphics for allele-specific expression.

Sequencing the transcriptome can answer various questions such as determining the transcripts expressed in a given species for a specific tissue or condition, evaluating differential expression, discovering variants, and evaluating allele-specific expression. Differential expression evaluates the expression differences between different strains, tissues, and conditions. Allele-specific expression evaluates expression differences between parental alleles. Both differential expression and allele-specific expression have been studied for heterosis (hybrid vigor), where the hybrid has improved performance over the parents for one or more traits. The Allele Workbench software was developed for a heterosis study that evaluated allele-specific expression for a mouse F1 hybrid using libraries from multiple tissues with biological replicates. This software has been made into a distributable package, which includes a pipeline, a Java interface to build the database, and a Java interface for query and display of the results. The required input is a reference genome, annotation file, and one or more RNA-Seq libraries with optional replicates. It evaluates allelic imbalance at the SNP and transcript level and flags transcripts with significant opposite directional allele-specific expression. The Java interface allows the user to view data from libraries, replicates, genes, transcripts, exons, and variants, including queries on allele imbalance for selected libraries. To determine the impact of allele-specific SNPs on protein folding, variants are annotated with their effect (e.g., missense), and the parental protein sequences may be exported for protein folding analysis. The Allele Workbench processing results in transcript files and read counts that can be used as input to the previously published Transcriptome Computational Workbench, which has a new algorithm for determining a trimmed set of gene ontology terms. The software with demo files is available from https://code.google.com/p/allele-workbench. Additionally, all software is ready for immediate use from an Atmosphere Virtual Machine Image available from the iPlant Collaborative (www.iplantcollaborative.org).

A systems-wide comparison of red rice (Oryza longistaminata) tissues identifies rhizome specific genes and proteins that are targets for cultivated rice improvement.

BACKGROUND: The rhizome, the original stem of land plants, enables species to invade new territory and is a critical component of perenniality, especially in grasses. Red rice (Oryza longistaminata) is a perennial wild rice species with many valuable traits that could be used to improve cultivated rice cultivars, including rhizomatousness, disease resistance and drought tolerance. Despite these features, little is known about the molecular mechanisms that contribute to rhizome growth, development and function in this plant. RESULTS: We used an integrated approach to compare the transcriptome, proteome and metabolome of the rhizome to other tissues of red rice. 116 Gb of transcriptome sequence was obtained from various tissues and used to identify rhizome-specific and preferentially expressed genes, including transcription factors and hormone metabolism and stress response-related genes. Proteomics and metabolomics approaches identified 41 proteins and more than 100 primary metabolites and plant hormones with rhizome preferential accumulation. Of particular interest was the identification of a large number of gene transcripts from Magnaportha oryzae, the fungus that causes rice blast disease in cultivated rice, even though the red rice plants showed no sign of disease. CONCLUSIONS: A significant set of genes, proteins and metabolites appear to be specifically or preferentially expressed in the rhizome of O. longistaminata. The presence of M. oryzae gene transcripts at a high level in apparently healthy plants suggests that red rice is resistant to this pathogen, and may be able to provide genes to cultivated rice that will enable resistance to rice blast disease.

Making a living while starving in the dark: metagenomic insights into the energy dynamics of a carbonate cave.

Carbonate caves represent subterranean ecosystems that are largely devoid of phototrophic primary production. In semiarid and arid regions, allochthonous organic carbon inputs entering caves with vadose-zone drip water are minimal, creating highly oligotrophic conditions; however, past research indicates that carbonate speleothem surfaces in these caves support diverse, predominantly heterotrophic prokaryotic communities. The current study applied a metagenomic approach to elucidate the community structure and potential energy dynamics of microbial communities, colonizing speleothem surfaces in Kartchner Caverns, a carbonate cave in semiarid, southeastern Arizona, USA. Manual inspection of a speleothem metagenome revealed a community genetically adapted to low-nutrient conditions with indications that a nitrogen-based primary production strategy is probable, including contributions from both Archaea and Bacteria. Genes for all six known CO2-fixation pathways were detected in the metagenome and RuBisCo genes representative of the Calvin-Benson-Bassham cycle were over-represented in Kartchner speleothem metagenomes relative to bulk soil, rhizosphere soil and deep-ocean communities. Intriguingly, quantitative PCR found Archaea to be significantly more abundant in the cave communities than in soils above the cave. MEtaGenome ANalyzer (MEGAN) analysis of speleothem metagenome sequence reads found Thaumarchaeota to be the third most abundant phylum in the community, and identified taxonomic associations to this phylum for indicator genes representative of multiple CO2-fixation pathways. The results revealed that this oligotrophic subterranean environment supports a unique chemoautotrophic microbial community with potentially novel nutrient cycling strategies. These strategies may provide key insights into other ecosystems dominated by oligotrophy, including aphotic subsurface soils or aquifers and photic systems such as arid deserts.

TCW: transcriptome computational workbench.

BACKGROUND: The analysis of transcriptome data involves many steps and various programs, along with organization of large amounts of data and results. Without a methodical approach for storage, analysis and query, the resulting ad hoc analysis can lead to human error, loss of data and results, inefficient use of time, and lack of verifiability, repeatability, and extensibility. METHODOLOGY: The Transcriptome Computational Workbench (TCW) provides Java graphical interfaces for methodical analysis for both single and comparative transcriptome data without the use of a reference genome (e.g. for non-model organisms). The singleTCW interface steps the user through importing transcript sequences (e.g. Illumina) or assembling long sequences (e.g. Sanger, 454, transcripts), annotating the sequences, and performing differential expression analysis using published statistical programs in R. The data, metadata, and results are stored in a MySQL database. The multiTCW interface builds a comparison database by importing sequence and annotation from one or more single TCW databases, executes the ESTscan program to translate the sequences into proteins, and then incorporates one or more clusterings, where the clustering options are to execute the orthoMCL program, compute transitive closure, or import clusters. Both singleTCW and multiTCW allow extensive query and display of the results, where singleTCW displays the alignment of annotation hits to transcript sequences, and multiTCW displays multiple transcript alignments with MUSCLE or pairwise alignments. The query programs can be executed on the desktop for fastest analysis, or from the web for sharing the results. CONCLUSION: It is now affordable to buy a multi-processor machine, and easy to install Java and MySQL. By simply downloading the TCW, the user can interactively analyze, query and view their data. The TCW allows in-depth data mining of the results, which can lead to a better understanding of the transcriptome. TCW is freely available from www.agcol.arizona.edu/software/tcw.

Ginger and turmeric expressed sequence tags identify signature genes for rhizome identity and development and the biosynthesis of curcuminoids, gingerols and terpenoids.

BACKGROUND: Ginger (Zingiber officinale) and turmeric (Curcuma longa) accumulate important pharmacologically active metabolites at high levels in their rhizomes. Despite their importance, relatively little is known regarding gene expression in the rhizomes of ginger and turmeric. RESULTS: In order to identify rhizome-enriched genes and genes encoding specialized metabolism enzymes and pathway regulators, we evaluated an assembled collection of expressed sequence tags (ESTs) from eight different ginger and turmeric tissues. Comparisons to publicly available sorghum rhizome ESTs revealed a total of 777 gene transcripts expressed in ginger/turmeric and sorghum rhizomes but apparently absent from other tissues. The list of rhizome-specific transcripts was enriched for genes associated with regulation of tissue growth, development, and transcription. In particular, transcripts for ethylene response factors and AUX/IAA proteins appeared to accumulate in patterns mirroring results from previous studies regarding rhizome growth responses to exogenous applications of auxin and ethylene. Thus, these genes may play important roles in defining rhizome growth and development. Additional associations were made for ginger and turmeric rhizome-enriched MADS box transcription factors, their putative rhizome-enriched homologs in sorghum, and rhizomatous QTLs in rice. Additionally, analysis of both primary and specialized metabolism genes indicates that ginger and turmeric rhizomes are primarily devoted to the utilization of leaf supplied sucrose for the production and/or storage of specialized metabolites associated with the phenylpropanoid pathway and putative type III polyketide synthase gene products. This finding reinforces earlier hypotheses predicting roles of this enzyme class in the production of curcuminoids and gingerols. CONCLUSION: A significant set of genes were found to be exclusively or preferentially expressed in the rhizome of ginger and turmeric. Specific transcription factors and other regulatory genes were found that were common to the two species and that are excellent candidates for involvement in rhizome growth, differentiation and development. Large classes of enzymes involved in specialized metabolism were also found to have apparent tissue-specific expression, suggesting that gene expression itself may play an important role in regulating metabolite production in these plants.

Draft genome sequence of chickpea (Cicer arietinum) provides a resource for trait improvement.

Chickpea (Cicer arietinum) is the second most widely grown legume crop after soybean, accounting for a substantial proportion of human dietary nitrogen intake and playing a crucial role in food security in developing countries. We report the ∼738-Mb draft whole genome shotgun sequence of CDC Frontier, a kabuli chickpea variety, which contains an estimated 28,269 genes. Resequencing and analysis of 90 cultivated and wild genotypes from ten countries identifies targets of both breeding-associated genetic sweeps and breeding-associated balancing selection. Candidate genes for disease resistance and agronomic traits are highlighted, including traits that distinguish the two main market classes of cultivated chickpea--desi and kabuli. These data comprise a resource for chickpea improvement through molecular breeding and provide insights into both genome diversity and domestication.

Profiling bacterial diversity and taxonomic composition on speleothem surfaces in Kartchner Caverns, AZ.

Caves are relatively accessible subterranean habitats ideal for the study of subsurface microbial dynamics and metabolisms under oligotrophic, non-photosynthetic conditions. A 454-pyrotag analysis of the V6 region of the 16S rRNA gene was used to systematically evaluate the bacterial diversity of ten cave surfaces within Kartchner Caverns, a limestone cave. Results showed an average of 1,994 operational taxonomic units (97 % cutoff) per speleothem and a broad taxonomic diversity that included 21 phyla and 12 candidate phyla. Comparative analysis of speleothems within a single room of the cave revealed three distinct bacterial taxonomic profiles dominated by either Actinobacteria, Proteobacteria, or Acidobacteria. A gradient in observed species richness along the sampling transect revealed that the communities with lower diversity corresponded to those dominated by Actinobacteria while the more diverse communities were those dominated by Proteobacteria. A 16S rRNA gene clone library from one of the Actinobacteria-dominated speleothems identified clones with 99 % identity to chemoautotrophs and previously characterized oligotrophs, providing insights into potential energy dynamics supporting these communities. The robust analysis conducted for this study demonstrated a rich bacterial diversity on speleothem surfaces. Further, it was shown that seemingly comparable speleothems supported divergent phylogenetic profiles suggesting that these communities are very sensitive to subtle variations in nutritional inputs and environmental factors typifying speleothem surfaces in Kartchner Caverns.

An elm EST database for identifying leaf beetle egg-induced defense genes.

BACKGROUND: Plants can defend themselves against herbivorous insects prior to the onset of larval feeding by responding to the eggs laid on their leaves. In the European field elm (Ulmus minor), egg laying by the elm leaf beetle ( Xanthogaleruca luteola) activates the emission of volatiles that attract specialised egg parasitoids, which in turn kill the eggs. Little is known about the transcriptional changes that insect eggs trigger in plants and how such indirect defense mechanisms are orchestrated in the context of other biological processes. RESULTS: Here we present the first large scale study of egg-induced changes in the transcriptional profile of a tree. Five cDNA libraries were generated from leaves of (i) untreated control elms, and elms treated with (ii) egg laying and feeding by elm leaf beetles, (iii) feeding, (iv) artificial transfer of egg clutches, and (v) methyl jasmonate. A total of 361,196 ESTs expressed sequence tags (ESTs) were identified which clustered into 52,823 unique transcripts (Unitrans) and were stored in a database with a public web interface. Among the analyzed Unitrans, 73% could be annotated by homology to known genes in the UniProt (Plant) database, particularly to those from Vitis, Ricinus, Populus and Arabidopsis. Comparative in silico analysis among the different treatments revealed differences in Gene Ontology term abundances. Defense- and stress-related gene transcripts were present in high abundance in leaves after herbivore egg laying, but transcripts involved in photosynthesis showed decreased abundance. Many pathogen-related genes and genes involved in phytohormone signaling were expressed, indicative of jasmonic acid biosynthesis and activation of jasmonic acid responsive genes. Cross-comparisons between different libraries based on expression profiles allowed the identification of genes with a potential relevance in egg-induced defenses, as well as other biological processes, including signal transduction, transport and primary metabolism. CONCLUSION: Here we present a dataset for a large-scale study of the mechanisms of plant defense against insect eggs in a co-evolved, natural ecological plant-insect system. The EST database analysis provided here is a first step in elucidating the transcriptional responses of elm to elm leaf beetle infestation, and adds further to our knowledge on insect egg-induced transcriptomic changes in plants. The sequences identified in our comparative analysis give many hints about novel defense mechanisms directed towards eggs.

Life at the hyperarid margin: novel bacterial diversity in arid soils of the Atacama Desert, Chile.

Nearly half the earth's surface is occupied by dryland ecosystems, regions susceptible to reduced states of biological productivity caused by climate fluctuations. Of these regions, arid zones located at the interface between vegetated semiarid regions and biologically unproductive hyperarid zones are considered most vulnerable. The objective of this study was to conduct a deep diversity analysis of bacterial communities in unvegetated arid soils of the Atacama Desert, to characterize community structure and infer the functional potential of these communities based on observed phylogenetic associations. A 454-pyrotag analysis was conducted of three unvegetated arid sites located at the hyperarid-arid margin. The analysis revealed communities with unique bacterial diversity marked by high abundances of novel Actinobacteria and Chloroflexi and low levels of Acidobacteria and Proteobacteria, phyla that are dominant in many biomes. A 16S rRNA gene library of one site revealed the presence of clones with phylogenetic associations to chemoautotrophic taxa able to obtain energy through oxidation of nitrite, carbon monoxide, iron, or sulfur. Thus, soils at the hyperarid margin were found to harbor a wealth of novel bacteria and to support potentially viable communities with phylogenetic associations to non-phototrophic primary producers and bacteria capable of biogeochemical cycling.

Next-generation sequencing-based transcriptomic and proteomic analysis of the common reed, Phragmites australis (Poaceae), reveals genes involved in invasiveness and rhizome specificity.

PREMISE OF THE STUDY: The common reed (Phragmites australis), one of the most widely distributed of all angiosperms, uses its rhizomes (underground stems) to invade new territory, making it one of the most successful weedy species worldwide. Characterization of the rhizome transcriptome and proteome is needed to identify candidate genes and proteins involved in rhizome growth, development, metabolism, and invasiveness. METHODS: We employed next-generation sequencing technologies including 454 and Illumina platforms to characterize the reed rhizome transcriptome and used quantitative proteomics techniques to identify the rhizome proteome. KEY RESULTS: Combining 336514 Roche 454 Titanium reads and 103350802 Illumina paired-end reads in a de novo hybrid assembly yielded 124450 unique transcripts with an average length of 549 bp, of which 54317 were annotated. Rhizome-specific and differentially expressed transcripts were identified between rhizome apical tips (apical meristematic region) and rhizome elongation zones. A total of 1280 nonredundant proteins were identified and quantified using GeLC-MS/MS based label-free proteomics, where 174 and 77 proteins were preferentially expressed in the rhizome elongation zone and apical tip tissues, respectively. Genes involved in allelopathy and in controlling development and potentially invasiveness were identified. CONCLUSIONS: In addition to being a valuable sequence and protein data resource for studying plant rhizome species, our results provide useful insights into identifying specific genes and proteins with potential roles in rhizome differentiation, development, and function.

MGOS: development of a community annotation database for Magnaporthe oryzae.

Magnaporthe oryzae causes rice blast disease, which is the most serious disease of cultivated rice worldwide. We previously developed the Magnaporthe grisea-Orzya sativa (MGOS) database as a repository for the M. oryzae and rice genome sequences together with a comprehensive set of functional interaction data generated by a major consortium of U.S. researchers. The MGOS database has now undergone a major redesign to include data from the international blast research community, accessible with a new intuitive, easy-to-use interface. Registered database users can manually annotate gene sequences and features as well as add mutant data and literature on individual gene pages. Over 900 genes have been manually curated based on various biological databases and the scientific literature. Gene names and descriptions, gene ontology annotations, published and unpublished information on mutants and their phenotypes, responses in diverse microarray analyses, and related literature have been incorporated. Thus far, 362 M. oryzae genes have associated information on mutants. MGOS is now poised to become a one-stop repository for all structural and functional data available on all genes of this critically important rice pathogen.

SyMAP v3.4: a turnkey synteny system with application to plant genomes.

SyMAP (Synteny Mapping and Analysis Program) was originally developed to compute synteny blocks between a sequenced genome and a FPC map, and has been extended to support pairs of sequenced genomes. SyMAP uses MUMmer to compute the raw hits between the two genomes, which are then clustered and filtered using the optional gene annotation. The filtered hits are input to the synteny algorithm, which was designed to discover duplicated regions and form larger-scale synteny blocks, where intervening micro-rearrangements are allowed. SyMAP provides extensive interactive Java displays at all levels of resolution along with simultaneous displays of multiple aligned pairs. The synteny blocks from multiple chromosomes may be displayed in a high-level dot plot or three-dimensional view, and the user may then drill down to see the details of a region, including the alignments of the hits to the gene annotation. These capabilities are illustrated by showing their application to the study of genome duplication, differential gene loss and transitive homology between sorghum, maize and rice. The software may be used from a website or standalone for the best performance. A project manager is provided to organize and automate the analysis of multi-genome groups. The software is freely distributed at http://www.agcol.arizona.edu/software/symap.

Comparative functional genomic analysis of Solanum glandular trichome types.

Glandular trichomes play important roles in protecting plants from biotic attack by producing defensive compounds. We investigated the metabolic profiles and transcriptomes to characterize the differences between different glandular trichome types in several domesticated and wild Solanum species: Solanum lycopersicum (glandular trichome types 1, 6, and 7), Solanum habrochaites (types 1, 4, and 6), Solanum pennellii (types 4 and 6), Solanum arcanum (type 6), and Solanum pimpinellifolium (type 6). Substantial chemical differences in and between Solanum species and glandular trichome types are likely determined by the regulation of metabolism at several levels. Comparison of S. habrochaites type 1 and 4 glandular trichomes revealed few differences in chemical content or transcript abundance, leading to the conclusion that these two glandular trichome types are the same and differ perhaps only in stalk length. The observation that all of the other species examined here contain either type 1 or 4 trichomes (not both) supports the conclusion that these two trichome types are the same. Most differences in metabolites between type 1 and 4 glands on the one hand and type 6 glands on the other hand are quantitative but not qualitative. Several glandular trichome types express genes associated with photosynthesis and carbon fixation, indicating that some carbon destined for specialized metabolism is likely fixed within the trichome secretory cells. Finally, Solanum type 7 glandular trichomes do not appear to be involved in the biosynthesis and storage of specialized metabolites and thus likely serve another unknown function, perhaps as the site of the synthesis of protease inhibitors.

Computational techniques for elucidating plant-pathogen interactions from large-scale experiments on fungi and oomycetes.

Eukaryotic plant pathogens are responsible for the destruction of billions of dollars worth of crops each year. With large-scale genomics of both pathogens and hosts and the corresponding computational analysis, biologists are now able to gain knowledge about many pathogenic and defense genes concurrently. To study the interactions between these two organism groups, it is necessary to design experiments to elucidate the genes being expressed during the invasion of the pathogen into the host. For the most part, this does not require new software development, though it does require the use of existing software in novel ways. This article provides a broad overview of several key and illustrative experiments and the corresponding computational analyses, outlining the knowledge gained in each. It goes on to describe databases for plant-pathogen data and important initiatives such as Plant-Associated Microbe Gene Ontology. It discusses how various emerging approaches will increase the power of computers in host-pathogen interaction studies.

Sequencing, mapping, and analysis of 27,455 maize full-length cDNAs.

Full-length cDNA (FLcDNA) sequencing establishes the precise primary structure of individual gene transcripts. From two libraries representing 27 B73 tissues and abiotic stress treatments, 27,455 high-quality FLcDNAs were sequenced. The average transcript length was 1.44 kb including 218 bases and 321 bases of 5' and 3' UTR, respectively, with 8.6% of the FLcDNAs encoding predicted proteins of fewer than 100 amino acids. Approximately 94% of the FLcDNAs were stringently mapped to the maize genome. Although nearly two-thirds of this genome is composed of transposable elements (TEs), only 5.6% of the FLcDNAs contained TE sequences in coding or UTR regions. Approximately 7.2% of the FLcDNAs are putative transcription factors, suggesting that rare transcripts are well-enriched in our FLcDNA set. Protein similarity searching identified 1,737 maize transcripts not present in rice, sorghum, Arabidopsis, or poplar annotated genes. A strict FLcDNA assembly generated 24,467 non-redundant sequences, of which 88% have non-maize protein matches. The FLcDNAs were also assembled with 41,759 FLcDNAs in GenBank from other projects, where semi-strict parameters were used to identify 13,368 potentially unique non-redundant sequences from this project. The libraries, ESTs, and FLcDNA sequences produced from this project are publicly available. The annotated EST and FLcDNA assemblies are available through the maize FLcDNA web resource (www.maizecdna.org).

A BAC-based physical map of Brachypodium distachyon and its comparative analysis with rice and wheat.

BACKGROUND: Brachypodium distachyon (Brachypodium) has been recognized as a new model species for comparative and functional genomics of cereal and bioenergy crops because it possesses many biological attributes desirable in a model, such as a small genome size, short stature, self-pollinating habit, and short generation cycle. To maximize the utility of Brachypodium as a model for basic and applied research it is necessary to develop genomic resources for it. A BAC-based physical map is one of them. A physical map will facilitate analysis of genome structure, comparative genomics, and assembly of the entire genome sequence. RESULTS: A total of 67,151 Brachypodium BAC clones were fingerprinted with the SNaPshot HICF fingerprinting method and a genome-wide physical map of the Brachypodium genome was constructed. The map consisted of 671 contigs and 2,161 clones remained as singletons. The contigs and singletons spanned 414 Mb. A total of 13,970 gene-related sequences were detected in the BAC end sequences (BES). These gene tags aligned 345 contigs with 336 Mb of rice genome sequence, showing that Brachypodium and rice genomes are generally highly colinear. Divergent regions were mainly in the rice centromeric regions. A dot-plot of Brachypodium contigs against the rice genome sequences revealed remnants of the whole-genome duplication caused by paleotetraploidy, which were previously found in rice and sorghum. Brachypodium contigs were anchored to the wheat deletion bin maps with the BES gene-tags, opening the door to Brachypodium-Triticeae comparative genomics. CONCLUSION: The construction of the Brachypodium physical map, and its comparison with the rice genome sequence demonstrated the utility of the SNaPshot-HICF method in the construction of BAC-based physical maps. The map represents an important genomic resource for the completion of Brachypodium genome sequence and grass comparative genomics. A draft of the physical map and its comparisons with rice and wheat are available at http://phymap.ucdavis.edu/brachypodium/.