A WUSCHEL Homeobox Transcription Factor, OsWOX13, Enhances Drought Tolerance and Triggers Early Flowering in Rice.

Plants have evolved strategies to cope with drought stress by maximizing physiological capacity and adjusting developmental processes such as flowering time. The WOX13 orthologous group is the most conserved among the clade of WOX homeodomain-containing proteins and is found to function in both drought stress and flower development. In this study, we isolated and characterized OsWOX13 from rice. OsWOX13 was regulated spatially in vegetative organs but temporally in flowers and seeds. Overexpression of OsWOX13 (OsWOX13-ov) in rice under the rab21 promoter resulted in drought resistance and early flowering by 7-10 days. Screening of gene expression profiles in mature leaf and panicles of OsWOX13-ov showed a broad spectrum of effects on biological processes, such as abiotic and biotic stresses, exerting a cross-talk between responses. Protein binding microarray and electrophoretic mobility shift assay analyses supported ATTGATTG as the putative cis-element binding of OsWOX13. OsDREB1A and OsDREB1F, drought stress response transcription factors, contain ATTGATTG motif(s) in their promoters and are preferentially expressed in OsWOX13-ov. In addition, Heading date 3a and OsMADS14, regulators in the flowering pathway and development, were enhanced in OsWOX13-ov. These results suggest that OsWOX13 mediates the stress response and early flowering and, thus, may be a regulator of genes involved in drought escape.

Analysis of Genes with Alternatively Spliced Transcripts in the Leaf, Root, Panicle and Seed of Rice Using a Long Oligomer Microarray and RNA-Seq.

Pre-mRNA splicing further increases protein diversity acquired through evolution. The underlying driving forces for this phenomenon are unknown, especially in terms of gene expression. A rice alternatively spliced transcript detection microarray (ASDM) and RNA sequencing (RNA-Seq) were applied to differentiate the transcriptome of 4 representative organs of Oryza sativa L. cv. Ilmi: leaves, roots, 1-cm-stage panicles and young seeds at 21 days after pollination. Comparison of data obtained by microarray and RNA-Seq showed a bell-shaped distribution and a co-lineation for highly expressed genes. Transcripts were classified according to the degree of organ enrichment using a coefficient value (CV, the ratio of the standard deviation to the mean values): highly variable (CVI), variable (CVII), and constitutive (CVIII) groups. A higher index of the portion of loci with alternatively spliced transcripts in a group (IAST) value was observed for the constitutive group. Genes of the highly variable group showed the characteristics of the examined organs, and alternatively spliced transcripts tended to exhibit the same organ specificity or less organ preferences, with avoidance of 'organ distinctness'. In addition, within a locus, a tendency of higher expression was found for transcripts with a longer coding sequence (CDS), and a spliced intron was the most commonly found type of alternative splicing for an extended CDS. Thus, pre-mRNA splicing might have evolved to retain maximum functionality in terms of organ preference and multiplicity.

RapaNet: A Web Tool for the Co-Expression Analysis of Brassica rapa Genes.

Accumulated microarray data are used for assessing gene function by providing statistical values for co-expressed genes; however, only a limited number of Web tools are available for analyzing the co-expression of genes of Brassica rapa. We have developed a Web tool called RapaNet (http://bioinfo.mju.ac.kr/arraynet/brassica300k/query/), which is based on a data set of 143 B rapa microarrays compiled from various organs and at different developmental stages during exposure to biotic or abiotic stress. RapaNet visualizes correlated gene expression information via correlational networks and phylogenetic trees using Pearson correlation coefficient (r). In addition, RapaNet provides hierarchical clustering diagrams, scatterplots of log ratio intensities, related pathway maps, and cis-element lists of promoter regions. To ascertain the functionality of RapaNet, the correlated genes encoding ribosomal protein (L7Ae), photosystem II protein D1 (psbA), and cytochrome P450 monooxygenase in glucosinolate biosynthesis (CYP79F1) were retrieved from RapaNet and compared with their Arabidopsis homologues. An analysis of the co-expressed genes revealed their shared and unique features.

Genome-wide identification of grain filling genes regulated by the OsSMF1 transcription factor in rice.

BACKGROUND: Spatial- and temporal-specific expression patterns are primarily regulated at the transcriptional level by gene promoters. Therefore, it is important to identify the binding motifs of transcription factors to better understand the networks associated with embryogenesis. RESULTS: Here, we used a protein-binding microarray (PBM) to identify the binding motifs of OsSMF1, which is a basic leucine zipper transcription factor involved in the regulation of rice seed maturation. OsSMF1 (previously called RISBZ1 or OsbZIP58) is known to interact with GCN4 motifs (TGA(G/C)TCA) to regulate seed storage protein synthesis, and it functions as a key regulator of starch synthesis. Quadruple 9-mer-based PBM analysis and electrophoretic mobility shift assay revealed that OsSMF1 bound to the GCN4 (TGA(G/C)TCA), ACGT (CCACGT(C/G)), and ATGA (GGATGAC) motifs with three different affinities. We predicted 44 putative OsSMF1 target genes using data obtained from both the PBM and RiceArrayNet. Among these putative target genes, 18, 21, and 13 genes contained GCN4, ACGT, and ATGA motifs within their 1-kb promoter regions, respectively. Among them, six genes encoding major grain filling proteins and transcription factors were chosen to confirm the activation of their expression in vivo. OsSMF1 was shown to bind directly to the promoters of Os03g0168500 (GCN4 motif), patatin-like gene (GCN4 motif), α-globulin (ACGT motif), rice prolamin box-binding factor (RPBF) (ATGA motif), and ONAC024 (GCN4 and ACGT motifs) and to regulate their expression. CONCLUSIONS: The results of this study suggest that OsSMF1 is one of the key transcription factors that functions in a wide range of seed developmental processes with different specific binding affinities for the three DNA-binding motifs.

A single module type I polyketide synthase directs de novo macrolactone biogenesis during galbonolide biosynthesis in Streptomyces galbus.

Galbonolide (GAL) A and B are antifungal macrolactone polyketides produced by Streptomyces galbus. During their polyketide chain assembly, GAL-A and -B incorporate methoxymalonate and methylmalonate, respectively, in the fourth chain extension step. The methoxymalonyl-acyl carrier protein biosynthesis locus (galG to K) is specifically involved in GAL-A biosynthesis, and this locus is neighbored by a gene cluster composed of galA-E. GalA-C constitute a single module, highly reducing type I polyketide synthase (PKS). GalD and GalE are cytochrome P450 and Rieske domain protein, respectively. Gene knock-out experiments verified that galB, -C, and -D are essential for GAL biosynthesis. A galD mutant accumulated a GAL-C that lacked two hydroxyl groups and a double bond when compared with GAL-B. A [U-(13)C]propionate feeding experiment indicated that no rare precursor other than methoxymalonate was incorporated during GAL biogenesis. A search of the S. galbus genome for a modular type I PKS system, the type that was expected to direct GAL biosynthesis, resulted in the identification of only one modular type I PKS gene cluster. Homology analysis indicated that this PKS gene cluster is the locus for vicenistatin biosynthesis. This cluster was previously reported in Streptomyces halstedii. A gene deletion of the vinP2 ortholog clearly demonstrated that this modular type I PKS system is not involved in GAL biosynthesis. Therefore, we propose that GalA-C direct macrolactone polyketide formation for GAL. Our studies provide a glimpse into a novel biochemical strategy used for polyketide synthesis; that is, the iterative assembly of propionates with highly programmed ß-keto group modifications.

A pepper MSRB2 gene confers drought tolerance in rice through the protection of chloroplast-targeted genes.

BACKGROUND: The perturbation of the steady state of reactive oxygen species (ROS) due to biotic and abiotic stresses in a plant could lead to protein denaturation through the modification of amino acid residues, including the oxidation of methionine residues. Methionine sulfoxide reductases (MSRs) catalyze the reduction of methionine sulfoxide back to the methionine residue. To assess the role of this enzyme, we generated transgenic rice using a pepper CaMSRB2 gene under the control of the rice Rab21 (responsive to ABA protein 21) promoter with/without a selection marker, the bar gene. RESULTS: A drought resistance test on transgenic plants showed that CaMSRB2 confers drought tolerance to rice, as evidenced by less oxidative stress symptoms and a strengthened PSII quantum yield under stress conditions, and increased survival rate and chlorophyll index after the re-watering. The results from immunoblotting using a methionine sulfoxide antibody and nano-LC-MS/MS spectrometry suggest that porphobilinogen deaminase (PBGD), which is involved in chlorophyll synthesis, is a putative target of CaMSRB2. The oxidized methionine content of PBGD expressed in E. coli increased in the presence of H2O2, and the Met-95 and Met-227 residues of PBGD were reduced by CaMSRB2 in the presence of dithiothreitol (DTT). An expression profiling analysis of the overexpression lines also suggested that photosystems are less severely affected by drought stress. CONCLUSIONS: Our results indicate that CaMSRB2 might play an important functional role in chloroplasts for conferring drought stress tolerance in rice.

Transcriptome analysis of leaf and root of rice seedling to acute dehydration.

BACKGROUND: Water deficiency is one of the most serious worldwide problems for agriculture. Recently, it has become more serious and outspread, which urgently requires the production of drought-tolerant plants. Microarray experiments using mRNA from air-dried leaves and roots of rice were performed in an attempt to study genes involved in acute dehydration response. RESULTS: Set of 10,537 rice genes was significantly up- or down-regulated in leaves or roots under the treatment. Gene Ontology analysis highlighted gene expression during acute dehydration response depending on organ types and the duration of stress. Rice responded by down-regulating many processes which are mainly involved in inhibiting growth and development. On the other hand, phytohormones (ABA, cytokinin, brassinosteroid) and protective molecules were induced to answer to multiple stresses. Leaves induced more genes than roots but those genes were scattered in various processes, most significantly were productions of osmoprotectants and precursors for important pathways in roots. Roots up-regulated fewer genes and focused on inducing antioxidants and enhancing photosynthesis. Myb, zf-C3HC4, and NAM were most strongly affected transcription factors with the dominance of leaf over root. CONCLUSIONS: Leaf and root tissues shared some common gene expression during stress, with the purpose of enhancing protective systems. However, these two tissues appeared to act differently in response to the different level of dehydration they experience. Besides, they can affect each other via the signaling and transportation system.

Abiotic stress responsive rice ASR1 and ASR3 exhibit different tissue-dependent sugar and hormone-sensitivities.

The expression of the six rice ASR genes is differentially regulated in a tissue-dependent manner according to environmental conditions and reproductive stages. OsASR1 and OsASR3 are the most abundant and are found in most tissues; they are enriched in the leaves and roots, respectively. Coexpression analysis of OsASR1 and OsASR3 and a comparison of the cis-acting elements upstream of OsASR1 and OsASR3 suggested that their expression is regulated in common by abiotic stresses but differently regulated by hormone and sugar signals. The results of quantitative real-time PCR analyses of OsASR1 and OsASR3 expression under various conditions further support this model. The expression of both OsASR1 and OsASR3 was induced by drought stress, which is a major regulator of the expression of all ASR genes in rice. In contrast, ABA is not a common regulator of the expression of these genes. OsASR1 transcription was highly induced by ABA, whereas OsASR3 transcription was strongly induced by GA. In addition, OsASR1 and OsASR3 expression was significantly induced by sucrose and sucrose/glucose treatments, respectively. The induction of gene expression in response to these specific hormone and sugar signals was primarily observed in the major target tissues of these genes (i.e., OsASR1 in leaves and OsASR3 in roots). Our data also showed that the overexpression of either OsASR1 or OsASR3 in transgenic rice plants increased their tolerance to drought and cold stress. Taken together, our results revealed that the transcriptional control of different rice ASR genes exhibit different tissue-dependent sugar and hormone-sensitivities.

Quadruple 9-mer-based protein binding microarray analysis confirms AACnG as the consensus nucleotide sequence sufficient for the specific binding of AtMYB44.

AtMYB44 is a member of the R2R3 MYB subgroup 22 transcription factors and regulates diverse cellular responses in Arabidopsis thaliana. We performed quadruple 9-merbased protein binding microarray (PBM) analysis, which revealed that full-size AtMYB44 recognized and bound to the consensus sequence AACnG, where n represents A, G, C or T. The consensus sequence was confirmed by electrophoretic mobility shift assay (EMSA) with a truncated AtMYB44 protein containing the N-terminal side R2R3 domain. This result indicates that the R2R3 domain alone is sufficient to exhibit AtMYB44 binding specificity. The sequence AACnG is the type I binding site for MYB transcription factors, including all members of the subgroup 22. EMSA showed that the R2R3 domain protein binds in vitro to promoters of randomly selected Arabidopsis genes that contain the consensus binding sequence. This implies that AtMYB44 binds to any promoter region that contains the consensus sequence, without determining their functional activity or specificity. The C-terminal side transcriptional activation domain of AtMYB44 contains an asparagine-rich fragment, NINNTTSSRHNHNN (aa 215-228), which, among the members of subgroup 22, is unique to AtMYB44. A transcriptional activation assay in yeast showed that this fragment is included in a region (aa 200-240) critical for the ability of AtMYB44 to function as a transcriptional activator. We hypothesize that the C-terminal side of the protein, but not the N-terminal side of the R2R3 domain, contributes to the functional activity and specificity of AtMYB44 through interactions with other regulators generated by each of a variety of stimuli.

An integrated PCR microfluidic chip incorporating aseptic electrochemical cell lysis and capillary electrophoresis amperometric DNA detection for rapid and quantitative genetic analysis.

A fully integrated microchip for performing cell lysis, polymerase chain reaction (PCR) and quantitative analysis of DNA amplicons in a single step is described herein. The chip was built on glass substrate using an indium-tin-oxide (ITO) microheater and PDMS engraved microchannels, which integrated an electrochemical cell lysis zone, a continuous flow PCR module and capillary electrophoresis amperometric detection (CE-AD) system. The total length of the microchannel was 4625 mm for performing 25 cycles of flow-through PCR and was laid on a handheld form factor of 96 × 96 mm(2) area. The key to the fabrication of such a device lies in the use of a single medium to carry out different kinds of biochemical reactions and hence, a reagentless electrochemical cell lysis protocol was integrated on the microchip which was capable of lysing most cell types, including difficult to lyse gram positive bacteria. The lysate contained genomic DNA from a sample which was proven to be suitable for PCR reactions. Genetic analysis was successfully performed on the microchip with purified lambda phage genomic DNA and various cell types, including non-tumorigenic MCF-10A and tumorigenic MCF-7 human cell lines, gram negative bacteria Escherichia coli O157:H7, and gram positive bacteria Bacillus subtilis, at an optimized flow rate of 5 µl min(-1). For the detection of amplicon DNA, a CE-AD system was used, with semisolid alkaline agarose within the capillary microchannel to minimize interference from cell debris and for efficient resolution of DNA fragments. High signal to noise ratio during amperometric detection and the use of online FFT filtering protocol enhanced the limit of detection of DNA amplicons. Therefore, with a combination of portability, cost-effectiveness and performance, the proposed integrated PCR microchip can be used for one step genetic analysis of most of the cell types and will enable more accessible healthcare.

FSTVAL: a new web tool to validate bulk flanking sequence tags.

BACKGROUND: Information about a transgene locus is one of the major concerns in transgenic research because expression of the transgene or a gene interrupted by the integration event could be affected. Thus, the flanking sequences obtained from transgenic plants need to be analyzed in terms of genomic context, such as genic and intergenic regions. This process may consist of several steps: 1) elimination of a vector sequence from the flanking sequence, 2) finding the locations in the target genome, and 3) statistics of the integration sites. These steps could be automated for flanking sequences from several dozens of transgenic plants generated in an ordinary targeted gene expression strategy. It would be indispensable in a genome-wide mutagenesis screen using T-DNA or transposons because these projects often generate several thousands of transgenic lines and just as many loci of the transgene among the transgenic plants. RESULTS: We present an open access web tool, flanking sequence tags validator (FSTVAL), to manage bulk flanking sequence tags (FSTs). FSTVAL automatically evaluates the FSTs and finds the best mapping positions of the FST against a known genome sequence. The statistics, in terms of genic and intergenic regions, are presented as a table, a distribution map, and a frequency graph along the chromosomes. Currently, 17 plant genome sequences, including Arabidopsis thaliana, Oryza sativa, and Glycine max, are available as reference genomes. We evaluated the utility and accuracy of the tool with 5,144 rice FSTs. The whole process, from uploading the sequences to generating tables of insertions, required a few minutes, with less than 4 clicks in the web environment. CONCLUSIONS: Run for 1 year and tested over 1,000 times, we have confirmed FSTVAL efficiently handles bulk FSTs. FSTVAL is freely available without login at http://bioinfo.mju.ac.kr/fstval/.

Convenient determination of protein-binding DNA sequences using quadruple 9-mer-based microarray and DsRed-monomer fusion protein.

Protein-binding DNA microarray (PBM) is one of the high-throughput methods to define DNA sequences which potentially bind to a given DNA-binding protein. Quadruple 9-mer-based protein-binding DNA microarray, named Q9-PBM, is designed in such a way that target probes are synthesized as quadruples of all possible 9-mer combinations. Also, recombinant proteins fused with DsRed-monomer fluorescent protein are conveniently constructed. Q9-PBM confirms the well-known DNA-binding sequences of Cbf1 and CBF1/DREB1B transcription factors, and also identifies the adjacent sequences. Moreover, Q9-PBM is applied to elucidate the unidentified cis-acting element of the OsNAC6 rice transcription factor. This technology will facilitate greater understanding of genome-wide interactions between proteins and DNA.

OsbHLH148, a basic helix-loop-helix protein, interacts with OsJAZ proteins in a jasmonate signaling pathway leading to drought tolerance in rice.

Jasmonates play important roles in development, stress responses and defense in plants. Here, we report the results of a study using a functional genomics approach that identified a rice basic helix-loop-helix domain gene, OsbHLH148, that conferred drought tolerance as a component of the jasmonate signaling module in rice. OsbHLH148 transcript levels were rapidly increased by treatment with methyl jasmonate (MeJA) or abscisic acid, and abiotic stresses including dehydration, high salinity, low temperature and wounding. Transgenic over-expression of OsbHLH148 in rice confers plant tolerance to drought stress. Expression profiling followed by DNA microarray and RNA gel-blot analyses of transgenic versus wild-type rice identified genes that are up-regulated by OsbHLH148 over-expression. These include OsDREB and OsJAZ genes that are involved in stress responses and the jasmonate signaling pathway, respectively. OsJAZ1, a rice ZIM domain protein, interacted with OsbHLH148 in yeast two-hybrid and pull-down assays, but it interacted with the putative OsCOI1 only in the presence of coronatine. Furthermore, the OsJAZ1 protein was degraded by rice and Arabidopsis extracts in the presence of coronatine, and its degradation was inhibited by MG132, a 26S proteasome inhibitor, suggesting 26S proteasome-mediated degradation of OsJAZ1 via the SCF(OsCOI1) complex. The transcription level of OsJAZ1 increased upon exposure of rice to MeJA. These results show that OsJAZ1 could act as a transcriptional regulator of the OsbHLH148-related jasmonate signaling pathway leading to drought tolerance. Thus, our study suggests that OsbHLH148 acts on an initial response of jasmonate-regulated gene expression toward drought tolerance, constituting the OsbHLH148-OsJAZ-OsCOI1 signaling module in rice.

Overexpression of the ethylene-responsive factor gene BrERF4 from Brassica rapa increases tolerance to salt and drought in Arabidopsis plants.

Ethylene-responsive factors (ERFs), within a subgroup of the AP2/ERF transcription factor family, are involved in diverse plant reactions to biotic or abiotic stresses. Here, we report that overexpression of an ERF gene from Brassica rapa ssp. pekinensis (BrERF4) led to improved tolerance to salt and drought stresses in Arabidopsis. It also significantly affected the growth and development of transgenic plants. We detected that salt-induced expressions of a transcriptional repressor gene, AtERF4, and some Ser/Thr protein phosphatase2C genes, ABI1, ABI2 and AtPP2CA, were suppressed in BrERF4-overexpressing Arabidopsis plants. Furthermore, BrERF4 was induced by treatment with ethylene or methyljasmonate, but not by abscisic acid or NaCl in B. rapa. These results suggest that BrERF4 is activated through a network of different signaling pathways in response to salinity and drought.

Complete genome sequence analysis of Leuconostoc kimchii IMSNU 11154.

Leuconostoc kimchii IMSNU 11154, isolated from kimchi, a traditional Korean fermented food, is known to be an important antimicrobial lactic acid bacterium with probiotic potential. Here we announce the complete genome sequence of L. kimchii IMSNU 11154 consisting of a 2,101,787-bp chromosome and five plasmids. The strain has genes for dextran formation from sucrose and for mannitol formation from fructose. Antimicrobial and antioxidative functions of L. kimchii IMSNU 11154 could be attributed to a leucosin B-like peptide and multiple enzymes to reduce hydrogen peroxide and oxidized thiols, respectively.

Quadruple 9-mer-based protein binding microarray with DsRed fusion protein.

BACKGROUND: The interaction between a transcription factor and DNA motif (cis-acting element) is an important regulatory step in gene regulation. Comprehensive genome-wide methods have been developed to characterize protein-DNA interactions. Recently, the universal protein binding microarray (PBM) was introduced to determine if a DNA motif interacts with proteins in a genome-wide manner. RESULTS: We facilitated the PBM technology using a DsRed fluorescent protein and a concatenated sequence of oligonucleotides. The PBM was designed in such a way that target probes were synthesized as quadruples of all possible 9-mer combinations, permitting unequivocal interpretation of the cis-acting elements. The complimentary DNA strands of the features were synthesized with a primer and DNA polymerase on microarray slides. Proteins were labeled via N-terminal fusion with DsRed fluorescent protein, which circumvents the need for a multi-step incubation. The PBM presented herein confirmed the well-known DNA binding sequences of Cbf1 and CBF1/DREB1B, and it was also applied to elucidate the unidentified cis-acting element of the OsNAC6 rice transcription factor. CONCLUSION: Our method demonstrated PBM can be conveniently performed by adopting: (1) quadruple 9-mers may increase protein-DNA binding interactions in the microarray, and (2) a one-step incubation shortens the wash and hybridization steps. This technology will facilitate greater understanding of genome-wide interactions between proteins and DNA.

RiceArrayNet: a database for correlating gene expression from transcriptome profiling, and its application to the analysis of coexpressed genes in rice.

Microarray data can be used to derive understanding of the relationships between the genes involved in various biological systems of an organism, given the availability of databases of gene expression measurements from the complete spectrum of experimental conditions and materials. However, there have been no reports, to date, of such a database being constructed for rice (Oryza sativa). Here, we describe the construction of such a database, called RiceArrayNet (RAN; http://www.ggbio.com/arraynet/), which provides information on coexpression between genes in terms of correlation coefficients (r values). The average number of coexpressed genes is 214, with sd of 440 at r >or= 0.5. Given the correlation between genes in a gene pair, the degrees of closeness between genes can be visualized in a relational tree and a relational network. The distribution of correlated genes according to degree of stringency shows how each gene is related to other genes. As an application of RAN, the 16-member L7Ae ribosomal protein family was explored for coexpressed genes and gene expression values within and between rice and Arabidopsis (Arabidopsis thaliana), and common and unique features in coexpression partners and expression patterns were observed for these family members. We observed a correlation pattern between Os01g0968800, a drought-responsive element-binding transcription factor, Os02g0790500, a trehalose-6-phosphate synthase, and Os06g0219500, a small heat shock factor, reflecting the fact that genes responding to the same biological stresses are regulated together. The RAN database can be used as a tool to gain insight into a particular gene by examining its coexpression partners.

Subcellular localization of rice histone deacetylases in organelles.

Histone deacetylases (HDACs) are known to function in the nucleus. Here, we report on the organellar localization of three rice HDACs, OsSIR2b, OsHDAC6, and OsHDAC10. The 35S:OsSIR2b-GFP and 35S:OsHDAC10-GFP constructs were introduced into tobacco BY2 cells. Co-localization analysis of the green fluorescent protein and MitoTracker fluorescent signals in the transformed BY2 cells indicated that OsSIR2b and OsHDAC10 are localized in the mitochondria. Transgenic Arabidopsis lines harboring 35S:OsHDAC6-GFP and 35S:OsHDAC10-GFP constructs were similarly analyzed, revealing that OsHDAC6-GFP is localized exclusively in chloroplasts, whereas OsHDAC10-GFP is localized in both mitochondria and chloroplasts. The presence of OsHDAC6-GFP and OsHDAC10-GFP in chloroplasts was verified by immunodetection.

The histone deacetylase OsHDAC1 epigenetically regulates the OsNAC6 gene that controls seedling root growth in rice.

We have previously isolated a rice gene encoding a histone deacetylase, OsHDAC1, and observed that its transgenic overexpression increases seedling root growth. To identify the transcriptional repression events that occur as a result of OsHDAC1 overexpression (OsHDAC1(OE)), a global profiling of root-expressed genes was performed on OsHDAC1(OE) or HDAC inhibitor-treated non-transgenic (NT) roots, in comparison with untreated NT roots. We selected 39 genes that are induced and repressed in HDAC inhibitor-treated NT and OsHDAC1(OE) roots, compared with NT roots, respectively. Interestingly, OsNAC6, a member of the NAM-ATAF-CUC (NAC) family, was identified as a key component of the OsHDAC1 regulon, and was found to be epigenetically repressed by OsHDAC1 overexpression. The root phenotype of OsNAC6 knock-out seedlings was observed to be similar to that of the OsHDAC1(OE) seedlings. Conversely, the root phenotype of the OsNAC6 overexpressors was similar to that of the OsHDAC1 knock-out seedlings. These observations indicate that OsHDAC1 negatively regulates the OsNAC6 gene that primarily mediates the alteration in the root growth of the OsHDAC1(OE) seedlings. Chromatin immunoprecipitation assays of the OsNAC6 promoter region using antibodies specific to acetylated histones H3 and H4 revealed that OsHDAC1 epigenetically represses the expression of OsNAC6 by deacetylating K9, K14 and K18 on H3 and K5, K12 and K16 on H4.

Complete genome sequence of Burkholderia glumae BGR1.

Burkholderia glumae is the causative agent of grain and seedling rot in rice and of bacterial wilt in many field crops. Here, we report the complete genome sequence of B. glumae BGR1 isolated from a diseased rice panicle in Korea.