Yozo Okazaki

RIKEN, Вако, Saitama, Japan

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Publications (23)121.88 Total impact

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    ABSTRACT: We investigated graft transmission of high-temperature tolerance in tomato scions to nontransgenic scions from transgenic rootstocks, where the fatty acid desaturase gene (LeFAD7) was RNA-silenced. Tomato was transformed with a plasmid carrying an inverted repeat of LeFAD7 by Agrobacterium. Several transgenic lines showed the lower amounts of LeFAD7 RNA and unsaturated fatty acids, while nontransgenic control did not, and siRNA was detected in the transgenic lines, but not in control. These lines grew under conditions of high temperature, while nontransgenic control did not. Further, the nontransgenic plants were grafted onto the silenced transgenic plants. The scions showed less of the target gene RNA, and siRNA was detected. Under high-temperature conditions, these grafted plants grew, while control grafted plants did not. Thus, it was shown that high-temperature tolerance was conferred in the nontransgenic scions after grafting onto the silenced rootstocks. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.
    Plant Biotechnology Journal 07/2015; DOI:10.1111/pbi.12429 · 5.68 Impact Factor
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    ABSTRACT: Environmental stress causes membrane damage in plants. Lipid studies are required to understand the adaptation of plants to climate change. Here, LC-MS-based lipidomic and microarray transcriptome analyses were carried out to elucidate the effect of short-term heat stress on the Arabidopsis thaliana leaf membrane. Vegetative plants were subjected to high temperatures for one day, and then grown under normal conditions. Sixty-six detected glycerolipid species were classified according to patterns of compositional change by Spearman's correlation coefficient. Triacylglycerols, 36:4- and 36:5-monogalactosyldiacylglycerol, 34:2- and 36:2-digalactosyldiacylglycerol, 34:1-, 36:1- and 36:6-phosphatidylcholine, and 34:1-phosphatidylethanolamine increased by the stress and immediately decreased during recovery. The relative amount of one triacylglycerol species (54:9) containing α-linolenic acid (18:3) increased under heat stress. These results suggest that heat stress in Arabidopsis leaves induces an increase in triacylglycerol levels, which functions as an intermediate of lipid turnover, and results in a decrease in membrane polyunsaturated fatty acids. Microarray data revealed candidate genes responsible for the observed metabolic changes.
    Scientific Reports 05/2015; 5:10533. DOI:10.1038/srep10533 · 5.58 Impact Factor
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    ABSTRACT: Glucuronosyldiacylglycerol (GlcADG) is a plant glycolipid that accumulates in Arabidopsis and rice in response to phosphorus (P) starvation. It has been suggested that GlcADG functions to mitigate the stress induced by phosphorus depletion. Biosynthesis of GlcADG requires sulfolipid (SQDG) synthase, which is coded for in plant genomes. This indicates the possibility that GlcADG may be a general constituent of membrane lipids in plants. In this study, we investigated the SQDG synthases found in the genomes of higher plants, ferns, mosses, algae, and cyanobacteria. In addition, we analyzed GlcADG accumulation, and the expression of SQDG synthase homologs in tomato and soybean plants grown under phosphorus-limited conditions. LC-MS analysis of lipids from these plants confirmed that GlcADG accumulated during phosphorus deprivation, as previously observed in Arabidopsis and rice. We also observed upregulation of SQDG synthase transcripts in these plants during P deprivation. These data suggest that GlcADG is present not only in model plants, but also in various other plant species, and that this lipid molecule performs an important physiological function as a mitigator of P-deprivation stress in plants. This article is protected by copyright. All rights reserved.
    Physiologia Plantarum 02/2015; DOI:10.1111/ppl.12334 · 3.26 Impact Factor
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    ABSTRACT: Rice (Oryza sativa) is an excellent resource, it comprises 25% of the total caloric intake of the world's population and rice plants yield many types of bioactive compounds. To determine the number of metabolites in rice and their chemical diversity, the metabolite composition of cultivated rice has been investigated with analytical techniques such as mass spectrometry (MS) and/or nuclear magnetic resonance spectroscopy and rice metabolite databases have been constructed. This review summarizes current knowledge on metabolites in rice including sugars, amino and organic acids, aromatic compounds, and phytohormones detected by gas chromatography-MS, liquid chromatography-MS, and capillary electrophoresis-MS. The biological properties and the activities of polar and non-polar metabolites produced by rice plants are also presented. Challenges in the estimation of the structure(s) of unknown metabolites by metabolomic approaches are introduced and discussed. Lastly, examples are presented of the successful application of metabolite profiling of rice to characterize gene(s) potentially critical for improving its quality by combining metabolite quantitative trait loci analysis, and to identify potential metabolite biomarkers that play a critical role when rice is grown under abiotic stress conditions.
    Molecular Plant 11/2014; 8(1). DOI:10.1093/mp/ssu125 · 6.61 Impact Factor
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    Tobias Kind · Yozo Okazaki · Kazuki Saito · Oliver Fiehn
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    ABSTRACT: This is a short supplement to the technical note "LipidBlast templates as flexible tools for creating new in-silico tandem mass spectral libraries". http://fiehnlab.ucdavis.edu/projects/LipidBlast contains the supplemental data (10 MByte) for the LipidBlast extension for the detection of glucuronosyldiacylglycerols (GlcADG) can be found under
  • Tobias Kind · Yozo Okazaki · Kazuki Saito · Oliver Fiehn
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    ABSTRACT: Tandem mass spectral libraries (MS/MS) are usually built by acquiring experimentally measured mass spectra from chemical reference compounds. We here show the versatility of in-silico or computer generated tandem mass spectra that are directly obtained from compound structures. We use the freely available LipidBlast development software to generate 15,000 MS/MS spectra of the glucuronosyldiacylglycerol (GlcADG) lipid class, recently discovered for the first time in plants. The generation of such an in-silico MS/MS library for positive and negative ionization mode took five hours development time, including the validation of the obtained mass spectra. Such libraries allow for high-throughput annotations of previously unknown glycolipids. The publicly available LipidBlast templates are universally applicable for the development of MS/MS libraries for novel lipid classes.
    Analytical Chemistry 10/2014; 86(22). DOI:10.1021/ac502511a · 5.83 Impact Factor
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    ABSTRACT: Plants produce structurally diverse secondary (specialized) metabolites to increase their fitness for survival under adverse environments. Several bioactive compounds for new drugs have been identified through screening of plant extracts. In this study, genome-wide association studies (GWAS) were conducted to investigate the genetic architecture behind the natural variation of rice secondary metabolites. GWAS using the metabolome data of 175 rice accessions successfully identified 323 associations among 143 SNPs and 89 metabolites. The data analysis highlighted that levels of many metabolites are tightly associated with a small number of strong QTLs. The tight association may be a mechanism generating strains with distinct metabolic composition through the crossing of 2 different strains. The results indicate that one plant species produce more diverse phytochemicals than previously expected, and plants still contain many useful compounds for human applications.This article is protected by copyright. All rights reserved.
    The Plant Journal 09/2014; 81(1). DOI:10.1111/tpj.12681 · 6.82 Impact Factor
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    ABSTRACT: Metabolomics plays an important role in phytochemical genomics and crop breeding; however, metabolite annotation is a significant bottleneck in metabolomic studies. In particular, in liquid chromatography–mass spectrometry (MS)-based metabolomics, which has become a routine technology for the profiling of plant-specialized metabolites, a substantial number of metabolites detected as MS peaks are still not assigned properly to a single metabolite. Oryza sativa (rice) is one of the most important staple crops in the world. In the present study, we isolated and elucidated the structures of specialized metabolites from rice by using MS/MS and NMR. Thirty-six compounds, including five new flavonoids and eight rare flavonolignan isomers, were isolated from the rice leaves. The MS/MS spectral data of the isolated compounds, with a detailed interpretation of MS fragmentation data, will facilitate metabolite annotation of the related phytochemicals by enriching the public mass spectral data depositories, including the plant-specific MS/MS-based database, ReSpect. Electronic supplementary material The online version of this article (doi:10.1007/s11306-013-0619-5) contains supplementary material, which is available to authorized users.
    Metabolomics 08/2014; 10(4):543-555. DOI:10.1007/s11306-013-0619-5 · 3.97 Impact Factor
  • Yozo Okazaki · Kazuki Saito
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    ABSTRACT: Lipids are the major constituents of biological membranes that can sense extracellular conditions. Lipid-mediated signaling occurs in response to various environmental stresses such as temperature change, salinity, drought, and pathogen attack. Lysophospholipid, fatty acid, phosphatidic acid, diacylglycerol, inositol phosphate, oxylipins, sphingolipid, and N-acylethanolamine have all been proposed to function as signaling lipids. Studies on these stress-inducible lipid species have demonstrated that each lipid class has specific biological relevance, biosynthetic mechanisms, and signaling cascades, which activate defense reactions at the transcriptional level. In addition to their roles in signaling, lipids also function as stress mitigators to reduce the intensity of stressors. To mitigate particular stresses, enhanced syntheses of unique lipids that accumulate in trace amounts under normal growth conditions are often observed under stressed conditions. Accumulation of oligogalactolipids and glucuronosyldiacylglycerol has recently been found to mitigate freezing and nutrition depletion stresses, respectively, during lipid remodeling. In addition, wax, cutin, and suberin, which are not constituents of the lipid bilayer but are components derived from lipids, contribute to the reduction of drought stress and tissue injury. These features indicate that lipid-mediated defenses against environmental stress contributes to plant survival.This article is protected by copyright. All rights reserved.
    The Plant Journal 05/2014; 79(4). DOI:10.1111/tpj.12556 · 6.82 Impact Factor
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    ABSTRACT: Information on crop genotype- and phenotype-metabolite associations can be of value to trait development as well as to food security and safety. The unique study presented here assessed seed metabolomic and ionomic diversity in a soybean lineage representing ~35 years of breeding (launch years 1972–2008) and increasing yield potential. Selected varieties included six conventional and three genetically modified (GM) glyphosate-tolerant lines. A metabolomics approach utilizing capillary electrophoresis (CE)-time-of-flight-mass spectrometry (TOF-MS), gas chromatography (GC)-TOF-MS and liquid chromatography (LC)-quadrupole (q)-TOFMS resulted in measurement of a total of 732 annotated peaks. Ionomics through inductively-coupled plasma (ICP)-MS profiled twenty mineral elements. Orthogonal partial least squares-discriminant analysis (OPLS-DA) of the seed data successfully differentiated newer higher-yielding soybean from earlier lower-yielding accessions at both field sites. This result reflected genetic fingerprinting data that demonstrated a similar distinction between the newer and older soybean. Correlation analysis also revealed associations between yield data and specific metabolites. There were no clear metabolic differences between the conventional and GM lines. Overall, observations of metabolic and genetic differences between older and newer soybean varieties provided novel and significant information on the impact of varietal development on biochemical variability. Proposed applications of omics in food and feed safety assessments will need to consider that GM is not a major source of metabolite variability and that trait development in crops will, of necessity, be associated with biochemical variation.
    Metabolomics 04/2014; 11(2). DOI:10.1007/s11306-014-0702-6 · 3.97 Impact Factor
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    ABSTRACT: In flowering plants, the tapetum, the innermost layer of the anther, provides both nutrient and lipid components to developing microspores, pollen grains, and the pollen coat. Though the programmed cell death of the tapetum is one of the most critical and sensitive steps for fertility and is affected by various environmental stresses, its regulatory mechanisms remain mostly unknown. Here we show that autophagy is required for the metabolic regulation and nutrient supply in anthers and that autophagic degradation within tapetum cells is essential for postmeiotic anther development in rice. Autophagosome-like structures and several vacuole-enclosed lipid bodies were observed in postmeiotic tapetum cells specifically at the uninucleate stage during pollen development, which were completely abolished in a retrotransposon-insertional OsATG7 (autophagy-related 7)-knockout mutant defective in autophagy, suggesting that autophagy is induced in tapetum cells. Surprisingly, the mutant showed complete sporophytic male sterility, failed to accumulate lipidic and starch components in pollen grains at the flowering stage, showed reduced pollen germination activity, and had limited anther dehiscence. Lipidomic analyses suggested impairment of editing of phosphatidylcholines and lipid desaturation in the mutant during pollen maturation. These results indicate a critical involvement of autophagy in a reproductive developmental process of rice, and shed light on the novel autophagy-mediated regulation of lipid metabolism in eukaryotic cells.
    Autophagy 03/2014; 10(5):878-888. DOI:10.4161/auto.28279 · 11.42 Impact Factor
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    ABSTRACT: Oil bodies are intracellular structures present in the seed and leaf cells of many land plants. Seed oil bodies are known to function as storage compartments for lipids. However, the physiological function of leaf oil bodies is unknown. Here we show that leaf oil bodies function as subcellular factories for the production of a stable phytoalexin in response to fungal infection and senescence. Proteomic analysis of oil bodies prepared from Arabidopsis thaliana leaves identified caleosin (CLO3) and α-dioxygenase (α-DOX1). Both CLO3 and α-DOX1 were localized on the surface of oil bodies. Infection with the pathogenic fungus Colletotrichum higginsianum promoted the formation of CLO3- and α-DOX1-positive oil bodies in perilesional areas surrounding the site of infection. α-DOX1 catalyzes the reaction from α-linolenic acid (a major fatty acid component of oil bodies) to an unstable compound, 2-hydroperoxy-octadecatrienoic acid (2-HPOT). Intriguingly, a combination of α-DOX1 and CLO3 produced a stable compound, 2-hydroxy-octadecatrienoic acid (2-HOT), from α-linolenic acid. This suggests that the colocalization of α-DOX1 and CLO3 on oil bodies might prevent the degradation of unstable 2-HPOT, by efficiently converting 2-HPOT into the stable compound 2-HOT. We found that 2-HOT had anti-fungal activity against members of the genus Colletotrichum and that infection with C. higginsianum induced 2-HOT production. These results defined 2-HOT as an A. thaliana phytoalexin. The present study provides the first evidence that leaf oil bodies produce a phytoalexin under a pathological condition, which suggests a new mechanism of plant defense.
    Plant physiology 11/2013; 164(1). DOI:10.1104/pp.113.230185 · 7.39 Impact Factor
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    ABSTRACT: Tomato (Solanum lycopersicum) fruit cuticle has been extensively studied due to its effect on the biochemical and physiological properties of the fruit. To date, several tomato mutants defective in proper cuticle formation have been identified. To gain insight into tomato cuticle formation, we investigated one such mutant, sticky peel/ light green (pe lg). We verified the responsible gene by fine mapping and obtained the same conclusion with the previous report. To elucidate the pleiotropic effects of cuticle deficiency caused by the cd2 mutation, CD2 suppression lines were constructed. As found in the pe lg mutant, the suppression lines showed enhanced water permeability and aberrant leaf and fruit cuticles. Water use efficiency of the suppression line was lower than that of the wild type. However, photosynthetic ability was not affected in the suppression line. Since these phenotypes are related to altered deposition of wax and cutin, other lipidic metabolites might be changed, too. To confirm this hypothesis, we conducted metabolite profiling. The metabolite profiling revealed that not only lipid but also sugar, flavonoid and glycoalkaloid metabolites in fruit were changed in the cd2 mutant. These results indicate that that CD2 is essential both for normal cutin and wax deposition and for proper accumulation of specific metabolites in tomato fruit.
    Plant and Cell Physiology 08/2013; 54. DOI:10.1093/pcp/pct100 · 4.98 Impact Factor
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    ABSTRACT: The local distribution of both the V-ATPase and the V-PPase, the main vacuolar proton pumps, were investigated in intact vacuoles isolated from Arabidopsis suspension-cultured cells. Fluorescent immunostaining showed that V-PPase was distributed evenly on the vacuolar membrane (VM), but V-ATPase localized to specific regions of the VM. We hypothesize that there may be membrane microdomains on the VM. To confirm this hypothesis, we prepared detergent-resistant membranes (DRM) from the VM in accordance with well established conventional methods. Analyses of fatty acid composition suggested that DRM had more saturated fatty acids compared with the whole VM in PC and PEP. In the proteomic analyses of both DRM and DSM, we confirmed the different local distributions of V-ATPase and V-PPase. The observations of DRM with an electron microscope supported the existence of different areas on the VM. Moreover, it was observed using total internal reflection fluorescent microscopy (TIRFM) that proton pumps were frequently immobilised at specific sites on the VM.In the proteomic analyses, we also found that many other vacuolar membrane proteins are distributed differently in DRM and DSM.Based on the results of this study, we discuss the possibility that VM microdomains might contribute to vacuolar dynamics.
    Plant and Cell Physiology 07/2013; 54(10). DOI:10.1093/pcp/pct107 · 4.98 Impact Factor
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    ABSTRACT: Plants synthesize a wide range of hydrophobic compounds, generally known as lipids. Here, we report an application of liquid chromatography ion trap time-of-flight mass spectrometry (LC-IT-TOF-MS) for plant lipidomics. Using hydrophilic interaction chromatography (HILIC) for class separation, typical membrane lipids including glycerolipids, steryl glucosides and glucosylceramides, and hydrophobic plant secondary metabolites such as saponins were analyzed simultaneously. By this method, we annotated approximately 100 molecules from Arabidopsis thaliana. To demonstrate the application of this method to biological study, we analyzed Arabidopsis mutant trigalactosyldiacylglycerol3 (tgd3), which has a complex metabolic phenotype including the accumulation of unusual forms of galactolipids. Lipid profiling by LC-MS revealed that tgd3 accumulated an unusual form of digalactosyldiacylglycerol, annotated as Gal(β1 → 6)βGalDG. The compositional difference between normal and unusual forms of digalactosyldiacylglycerol was detected by this method. In addition, we analyzed well-known Arabidopsis mutants ats1-1, fad6-1, and fad7-2, which are also disrupted in lipid metabolic genes. Untargeted lipidome analysis coupled with multivariate analysis clearly discriminated the mutants and their distinctive metabolites. These results indicated that HILIC-MS is an efficient method for plant lipidomics. Electronic supplementary material The online version of this article (doi:10.1007/s11306-011-0318-z) contains supplementary material, which is available to authorized users.
    Metabolomics 03/2013; 9(Suppl 1):121-131. DOI:10.1007/s11306-011-0318-z · 3.97 Impact Factor
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    ABSTRACT: Phosphorus supply is a major factor responsible for reduced crop yields. As a result, plants utilize various adaptive mechanisms against phosphorus depletion, including lipid remodelling. Here we report the involvement of a novel plant lipid, glucuronosyldiacylglycerol, against phosphorus depletion. Lipidomic analysis of Arabidopsis plants cultured in phosphorus-depleted conditions revealed inducible accumulation of glucuronosyldiacylglycerol. Investigation using a series of sulfolipid sulfoquinovosyldiacylglycerol synthesis-deficient mutants of Arabidopsis determined that the biosynthesis of glucuronosyldiacylglycerol shares the pathway of sulfoquinovosyldiacylglycerol synthesis in chloroplasts. Under phosphorus-depleted conditions, the Arabidopsis sqd2 mutant, which does not accumulate either sulfoquinovosyldiacylglycerol or glucuronosyldiacylglycerol, was the most severely damaged of three sulfoquinovosyldiacylglycerol-deficient mutants. As glucuronosyldiacylglycerol is still present in the other two mutants, this result indicates that glucuronosyldiacylglycerol has a role in the protection of plants against phosphorus limitation stress. Glucuronosyldiacylglycerol was also found in rice, and its concentration increased significantly following phosphorus limitation, suggesting a shared physiological significance of this novel lipid against phosphorus depletion in plants.
    Nature Communications 02/2013; 4:1510. DOI:10.1038/ncomms2512 · 10.74 Impact Factor
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    ABSTRACT: A comprehensive and large-scale metabolome quantitative trait loci (mQTL) analysis was performed to investigate the genetic backgrounds associated with metabolic phenotypes in rice grains. The metabolome dataset consisted of 759 metabolite signals obtained from the grains of 85 lines of rice (Oryza sativa, Sasanishiki × Habataki back-crossed inbred lines). Metabolome analysis was performed using four mass spectrometry pipelines to enhance detection of different classes of metabolites. This mQTL analysis of a wide range of metabolites highlighted an uneven distribution of 802 mQTLs on the rice genome, as well as different modes of metabolic trait (m-trait) control among various types of metabolites. The levels of most metabolites within rice grains were highly sensitive to environmental factors, but only weakly associated with mQTLs. Coordinated control was observed for several groups of metabolites, such as amino acids linked to the mQTL hotspot on chromosome 3. For flavonoids, m-trait variation among the experimental lines was tightly governed by genetic factors that alter the glycosylation of flavones. Many loci affecting levels of metabolites were detected by QTL analysis, and plausible gene candidates were evaluated by in silico analysis. Several mQTLs profoundly influenced metabolite levels, providing insight into the control of rice metabolism. The genomic region and genes potentially responsible for the biosynthesis of apigenin-6,8-di-C-α-l-arabinoside are presented as an example of a critical mQTL identified by the analysis.
    The Plant Journal 01/2012; 70(4):624-36. DOI:10.1111/j.1365-313X.2012.04903.x · 6.82 Impact Factor
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    Yozo Okazaki · Kazuki Saito
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    ABSTRACT: Biotechnology, including genetic modification, is a very important approach to regulate the production of particular metabolites in plants to improve their adaptation to environmental stress, to improve food quality, and to increase crop yield. Unfortunately, these approaches do not necessarily lead to the expected results due to the highly complex mechanisms underlying metabolic regulation in plants. In this context, metabolomics plays a key role in plant molecular biotechnology, where plant cells are modified by the expression of engineered genes, because we can obtain information on the metabolic status of cells via a snapshot of their metabolome. Although metabolome analysis could be used to evaluate the effect of foreign genes and understand the metabolic state of cells, there is no single analytical method for metabolomics because of the wide range of chemicals synthesized in plants. Here, we describe the basic analytical advancements in plant metabolomics and bioinformatics and the application of metabolomics to the biological study of plants.
    Plant Biotechnology Reports 01/2012; 6(1):1-15. DOI:10.1007/s11816-011-0191-2 · 1.59 Impact Factor
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    ABSTRACT: The physiological properties of rice grains are immediately obvious to consumers. High-coverage metabolomic characterization of the rice diversity research set predicted a negative correlation between fatty acid and lipid levels and amylose/total starch ratio (amylose ratio), but the reason for this is unclear. To obtain new insight into the relationships among the visual phenotypes of rice kernels, starch granule structures, amylose ratios, and metabolite changes, we investigated the metabolite changes of five Japonica cultivars with various amylose ratios and two knockout mutants (e1, a Starch synthase IIIa (SSIIIa)-deficient mutant and the SSIIIa/starch branching enzyme (BE) double-knockout mutant 4019) by using mass spectrometry-based metabolomics techniques. Scanning electron microscopy clearly showed that the two mutants had unusual starch granule structures. The metabolomic compositions of two cultivars with high amylose ratios (Hoshiyutaka and Yumetoiro) exhibited similar patterns, while that of the double-knockout mutant, which has an extremely high amylose ratio, differed. Rice pedigree network analysis of the cultivars and the mutants provided insight into the association between metabolic-trait properties and their underlying genetic basis in rice breeding in Japan. Multidimensional scaling analysis revealed that the Hoshiyutaka and Yumetoiro cultivars were Indica-like, yet they are classified as Japonica subpopulations. Exploring metabolomic traits is a powerful way to follow rice genetic traces and breeding history.
    Molecular Plant 12/2011; 5(2):442-51. DOI:10.1093/mp/ssr101 · 6.61 Impact Factor
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    ABSTRACT: Increasing awareness of limitations to natural resources has set high expectations for plant science to deliver efficient crops with increased yields, improved stress tolerance, and tailored composition. Collections of representative varieties are a valuable resource for compiling broad breeding germplasms that can satisfy these diverse needs. Here we show that the untargeted high-coverage metabolomic characterization of such core collections is a powerful approach for studying the molecular backgrounds of quality traits and for constructing predictive metabolome-trait models. We profiled the metabolic composition of kernels from field-grown plants of the rice diversity research set using 4 complementary analytical platforms. We found that the metabolite profiles were correlated with both the overall population structure and fine-grained genetic diversity. Multivariate regression analysis showed that 10 of the 17 studied quality traits could be predicted from the metabolic composition independently of the population structure. Furthermore, the model of amylose ratio could be validated using external varieties grown in an independent experiment. Our results demonstrate the utility of metabolomics for linking traits with quantitative molecular data. This opens up new opportunities for trait prediction and construction of tailored germplasms to support modern plant breeding.
    BMC Systems Biology 10/2011; 5(1):176. DOI:10.1186/1752-0509-5-176 · 2.85 Impact Factor