Eli Kaminuma

Programmed induction of endoreduplication by DNA double-strand breaks in Arabidopsis

Genome integrity is continuously threatened by external stresses and endogenous hazards such as DNA replication errors and reactive oxygen species. The DNA damage checkpoint in metazoans ensures genome integrity by delaying cell-cycle progression to repair damaged DNA or by inducing apoptosis. ATM and ATR (ataxia-telangiectasia-mutated and -Rad3-related) are sensor kinases that relay the damage signal to transducer kinases Chk1 and Chk2 and to downstream cell-cycle regulators. Plants also possess ATM and ATR orthologs but lack obvious counterparts of downstream regulators. Instead, the plant-specific transcription factor SOG1 (suppressor of gamma response 1) plays a central role in the transmission of signals from both ATM and ATR kinases. Here we show that in Arabidopsis, endoreduplication is induced by DNA double-strand breaks (DSBs), but not directly by DNA replication stress. When root or sepal cells, or undifferentiated suspension cells, were treated with DSB inducers, they displayed increased cell size and DNA ploidy. We found that the ATM–SOG1 and ATR–SOG1 pathways both transmit DSB-derived signals and that either one suffices for endocycle induction. These signaling pathways govern the expression of distinct sets of cell-cycle regulators, such as cyclin-dependent kinases and their suppressors. Our results demonstrate that Arabidopsis undergoes a programmed endoreduplicative response to DSBs, suggesting that plants have evolved a distinct strategy to sustain growth under genotoxic stress.

Genome-wide suppression of aberrant mRNA-like noncoding RNAs by NMD in Arabidopsis

The nonsense-mediated mRNA decay (NMD) pathway is a well-known eukaryotic surveillance mechanism that eliminates aberrant mRNAs that contain a premature termination codon (PTC). The UP-Frameshift (UPF) proteins, UPF1, UPF2, and UPF3, are essential for normal NMD function. Several NMD substrates have been identified, but detailed information on NMD substrates is lacking. Here, we noticed that, in Arabidopsis, most of the mRNA-like nonprotein-coding RNAs (ncRNAs) have the features of an NMD substrate. We examined the expression profiles of 2 Arabidopsis mutants, upf1-1 and upf3-1, using a whole-genome tiling array. The results showed that expression of not only protein-coding transcripts but also many mRNA-like ncRNAs (mlncRNAs), including natural antisense transcript RNAs (nat-RNAs) transcribed from the opposite strands of the coding strands, were up-regulated in both mutants. The percentage of the up-regulated mlncRNAs to all expressed mlncRNAs was much higher than that of the up-regulated protein-coding transcripts to all expressed protein- coding transcripts. This finding demonstrates that one of the most important roles of NMD is the genome-wide suppression of the aberrant mlncRNAs including nat-RNAs.

DDBJ launches a new archive database with analytical tools for next-generation sequence data

The DNA Data Bank of Japan (DDBJ) (http://www.ddbj.nig.ac.jp) has collected and released 1 701 110 entries/1 116 138 614 bases between July 2008 and June 2009. A few highlighted data releases from DDBJ were the complete genome sequence of an endosymbiont within protist cells in the termite gut and Cap Analysis Gene Expression tags for human and mouse deposited from the Functional Annotation of the Mammalian cDNA consortium. In this period, we started a novel user announcement service using Really Simple Syndication (RSS) to deliver a list of data released from DDBJ on a daily basis. Comprehensive visualization of a DDBJ release data was attempted by using a word cloud program. Moreover, a new archive for sequencing data from next-generation sequencers, the ‘DDBJ Read Archive’ (DRA), was launched. Concurrently, for read data registered in DRA, a semi-automatic annotation tool called the ‘DDBJ Read Annotation Pipeline’ was released as a preliminary step. The pipeline consists of two parts: basic analysis for reference genome mapping and de novo assembly and high-level analysis of structural and functional annotations. These new services will aid users’ research and provide easier access to DDBJ databases.

DDBJ progress report

The DNA Data Bank of Japan (DDBJ, http://www.ddbj.nig.ac.jp) provides a nucleotide sequence archive database and accompanying database tools for sequence submission, entry retrieval and annotation analysis. The DDBJ collected and released 3 637 446 entries/2 272 231 889 bases between July 2009 and June 2010. A highlight of the released data was archive datasets from next-generation sequencing reads of Japanese rice cultivar, Koshihikari submitted by the National Institute of Agrobiological Sciences. In this period, we started a new archive for quantitative genomics data, the DDBJ Omics aRchive (DOR). The DOR stores quantitative data both from the microarray and high-throughput new sequencing platforms. Moreover, we improved the content of the DDBJ patent sequence, released a new submission tool of the DDBJ Sequence Read Archive (DRA) which archives massive raw sequencing reads, and enhanced a cloud computing-based analytical system from sequencing reads, the DDBJ Read Annotation Pipeline. In this article, we describe these new functions of the DDBJ databases and support tools.

Identification of the candidate genes regulated by RNA-directed DNA methylation in Arabidopsis.

RNA-directed DNA methylation (RdDM) is a process in which 24 nucleotide (nt) small interfering RNAs (siRNAs) guide de novo cytosine methylation in the homologous genomic DNA region. Of several factors involving 24 nt siRNA accumulation, RNA-dependent RNA polymerase 2 (RDR2) is a key component, because accumulation of 24 nt siRNA disappears in the Arabidopsis rdr2 mutant. Here, we compared expression profiles among wild-type, rdr2-1 and ddc (drm1drm2cmt3), DNA methyltransferase triple mutant, using a whole genome tiling array to identify the candidate genes directly downregulated by RdDM-related 24 nt siRNAs. Of the transcripts upregulated in the mutants, we searched for those whose coding regions or flanking regions have siRNA-generating loci. We found upregulated expression of 18 transcripts with AGI codes and 19 predicted transcriptional units (TUs) with siRNA loci in both rdr2-1 and ddc. Our study provided important information for understanding the relationship between RdDM and the identified candidate genes.

DDBJ Read Annotation Pipeline: A Cloud Computing-Based Pipeline for High-Throughput Analysis of Next-Generation Sequencing Data

High-performance next-generation sequencing (NGS) technologies are advancing genomics and molecular biological research. However, the immense amount of sequence data requires computational skills and suitable hardware resources that are a challenge to molecular biologists. The DNA Data Bank of Japan (DDBJ) of the National Institute of Genetics (NIG) has initiated a cloud computing-based analytical pipeline, the DDBJ Read Annotation Pipeline (DDBJ Pipeline), for a high-throughput annotation of NGS reads. The DDBJ Pipeline offers a user-friendly graphical web interface and processes massive NGS datasets using decentralized processing by NIG supercomputers currently free of charge. The proposed pipeline consists of two analysis components: basic analysis for reference genome mapping and de novo assembly and subsequent high-level analysis of structural and functional annotations. Users may smoothly switch between the two components in the pipeline, facilitating web-based operations on a supercomputer for high-throughput data analysis. Moreover, public NGS reads of the DDBJ Sequence Read Archive located on the same supercomputer can be imported into the pipeline through the input of only an accession number. This proposed pipeline will facilitate research by utilizing unified analytical workflows applied to the NGS data. The DDBJ Pipeline is accessible at http://p.ddbj.nig.ac.jp/.

DNA data bank of Japan (DDBJ) progress report

The DNA Data Bank of Japan Center (DDBJ Center; http://www.ddbj.nig.ac.jp) maintains and provides public archival, retrieval and analytical services for biological information. The contents of the DDBJ databases are shared with the US National Center for Biotechnology Information (NCBI) and the European Bioinformatics Institute (EBI) within the framework of the International Nucleotide Sequence Database Collaboration (INSDC). Since 2013, the DDBJ Center has been operating the Japanese Genotype-phenotype Archive (JGA) in collaboration with the National Bioscience Database Center (NBDC) in Japan. In addition, the DDBJ Center develops semantic web technologies for data integration and sharing in collaboration with the Database Center for Life Science (DBCLS) in Japan. This paper briefly reports on the activities of the DDBJ Center over the past year including submissions to databases and improvements in our services for data retrieval, analysis, and integration.

Complete genome sequence of Bradyrhizobium sp. S23321: insights into symbiosis evolution in soil oligotrophs.

Bradyrhizobium sp. S23321 is an oligotrophic bacterium isolated from paddy field soil. Although S23321 is phylogenetically close to Bradyrhizobium japonicum USDA110, a legume symbiont, it is unable to induce root nodules in siratro, a legume often used for testing Nod factor-dependent nodulation. The genome of S23321 is a single circular chromosome, 7,231,841 bp in length, with an average GC content of 64.3%. The genome contains 6,898 potential protein-encoding genes, one set of rRNA genes, and 45 tRNA genes. Comparison of the genome structure between S23321 and USDA110 showed strong colinearity; however, the symbiosis islands present in USDA110 were absent in S23321, whose genome lacked a chaperonin gene cluster (groELS3) for symbiosis regulation found in USDA110. A comparison of sequences around the tRNA-Val gene strongly suggested that S23321 contains an ancestral-type genome that precedes the acquisition of a symbiosis island by horizontal gene transfer. Although S23321 contains a nif (nitrogen fixation) gene cluster, the organization, homology, and phylogeny of the genes in this cluster were more similar to those of photosynthetic bradyrhizobia ORS278 and BTAi1 than to those on the symbiosis island of USDA110. In addition, we found genes encoding a complete photosynthetic system, many ABC transporters for amino acids and oligopeptides, two types (polar and lateral) of flagella, multiple respiratory chains, and a system for lignin monomer catabolism in the S23321 genome. These features suggest that S23321 is able to adapt to a wide range of environments, probably including low-nutrient conditions, with multiple survival strategies in soil and rhizosphere.

The DNA Data Bank of Japan launches a new resource, the DDBJ Omics Archive of functional genomics experiments

The DNA Data Bank of Japan (DDBJ; http://www.ddbj.nig.ac.jp) maintains and provides archival, retrieval and analytical resources for biological information. The central DDBJ resource consists of public, open-access nucleotide sequence databases including raw sequence reads, assembly information and functional annotation. Database content is exchanged with EBI and NCBI within the framework of the International Nucleotide Sequence Database Collaboration (INSDC). In 2011, DDBJ launched two new resources: the ‘DDBJ Omics Archive’ (DOR; http://trace.ddbj.nig.ac.jp/dor) and BioProject (http://trace.ddbj.nig.ac.jp/bioproject). DOR is an archival database of functional genomics data generated by microarray and highly parallel new generation sequencers. Data are exchanged between the ArrayExpress at EBI and DOR in the common MAGE-TAB format. BioProject provides an organizational framework to access metadata about research projects and the data from the projects that are deposited into different databases. In this article, we describe major changes and improvements introduced to the DDBJ services, and the launch of two new resources: DOR and BioProject.

DDBJ progress report: a new submission system for leading to a correct annotation

The DNA Data Bank of Japan (DDBJ; http://www.ddbj.nig.ac.jp) maintains and provides archival, retrieval and analytical resources for biological information. This database content is shared with the US National Center for Biotechnology Information (NCBI) and the European Bioinformatics Institute (EBI) within the framework of the International Nucleotide Sequence Database Collaboration (INSDC). DDBJ launched a new nucleotide sequence submission system for receiving traditional nucleotide sequence. We expect that the new submission system will be useful for many submitters to input accurate annotation and reduce the time needed for data input. In addition, DDBJ has started a new service, the Japanese Genotype–phenotype Archive (JGA), with our partner institute, the National Bioscience Database Center (NBDC). JGA permanently archives and shares all types of individual human genetic and phenotypic data. We also introduce improvements in the DDBJ services and databases made during the past year.