Tokihiko Nanjo

Forestry and Forest Products Research Institute, Kumamoto, Kumamoto Prefecture, Japan

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Publications (21)78.59 Total impact

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    ABSTRACT: In this study, to elucidate the mechanisms of adaptation and tolerance to ionizing radiation in woody plants, we investigated the various biological effects of γ-rays on the Lombardy poplar (Populus nigra L. var. italica Du Roi). We detected abnormal leaf shape and color, fusion, distorted venation, shortened internode, fasciation and increased axillary shoots in γ-irradiated poplar plants. Acute γ-irradiation with a dose of 100Gy greatly reduced the height, stem diameter and biomass of poplar plantlets. After receiving doses of 200 and 300Gy, all the plantlets stopped growing, and then most of them withered after 4-10 weeks of γ-irradiation. Comet assays showed that nuclear DNA in suspension-cultured poplar cells had been damaged by γ-rays. To determine whether DNA repair-related proteins are involved in the response to γ-rays in Lombardy poplars, we cloned the PnRAD51, PnLIG4, PnKU70, PnXRCC4, PnPCNA and PnOGG1 cDNAs and investigated their mRNA expression. The PnRAD51, PnLIG4, PnKU70, PnXRCC4 and PnPCNA mRNAs were increased by γ-rays, but the PnOGG1 mRNA was decreased. Moreover, the expression of PnLIG4, PnKU70 and PnRAD51 was also up-regulated by Zeocin known as a DNA cleavage agent. These observations suggest that the morphogenesis, growth and protective gene expression in Lombardy poplars are severely affected by the DNA damage and unknown cellular events caused by γ-irradiation.
    Journal of environmental radioactivity 01/2012; 109:19-28. · 1.47 Impact Factor
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    ABSTRACT: LHY/CCA1 genes play a key role in the plant circadian clock system and are highly conserved among plant species. However, the evolutionary process of the LHY/CCA1 gene family remains unclear in angiosperms. To obtain details of the phylogeny of these genes, this study characterized LHY/CCA1 genes in a model woody plant,Populus tree.The evolutionary process of angiosperm LHY/CCA1 genes was elucidated using three approaches: comparison of exon–intron structures, reconstruction of phylogenetic trees and examination of syntenic relationships. In addition, the molecular evolutionary rates and the expression patterns of Populus LHYs were analyzed.Gene duplication events of Populus LHYs and Arabidopsis LHY/CCA1 had occurred independently by different chromosomal duplication events arising in each evolutionary lineage. Populus LHYs were under purifying selection by estimating substitution rates of these genes. Further, Populus LHYs conserved diurnal expressions in leaves and stems but the transcripts of LHY2 were more abundant than those of LHY1 in Populus plants.This study uncovered phylogenetic relationships of the LHY/CCA1 gene family in angiosperms. In addition, the transcript abundance and the evolutionary differences between Populus LHY1 and LHY2 imply that Populus LHY2, rather than LHY1, may have a major role in the Populus clock system.
    New Phytologist 01/2009; 181(4):808-19. · 6.74 Impact Factor
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    ABSTRACT: Cryptomeria japonica D. Don is one of the most commercially important conifers in Japan. However, the allergic disease caused by its pollen is a severe public health problem in Japan. Since large-scale analysis of expressed sequence tags (ESTs) in the male strobili of C. japonica should help us to clarify the overall expression of genes during the process of pollen development, we constructed a full-length enriched cDNA library that was derived from male strobili at various developmental stages. We obtained 36,011 expressed sequence tags (ESTs) from either one or both ends of 19,437 clones derived from the cDNA library of C. japonica male strobili at various developmental stages. The 19,437 cDNA clones corresponded to 10,463 transcripts. Approximately 80% of the transcripts resembled ESTs from Pinus and Picea, while approximately 75% had homologs in Arabidopsis. An analysis of homologies between ESTs from C. japonica male strobili and known pollen allergens in the Allergome Database revealed that products of 180 transcripts exhibited significant homology. Approximately 2% of the transcripts appeared to encode transcription factors. We identified twelve genes for MADS-box proteins among these transcription factors. The twelve MADS-box genes were classified as DEF/GLO/GGM13-, AG-, AGL6-, TM3- and TM8-like MIKCC genes and type I MADS-box genes. Our full-length enriched cDNA library derived from C. japonica male strobili provides information on expression of genes during the development of male reproductive organs. We provided potential allergens in C. japonica. We also provided new information about transcription factors including MADS-box genes expressed in male strobili of C. japonica. Large-scale gene discovery using full-length cDNAs is a valuable tool for studies of gymnosperm species.
    BMC Genomics 09/2008; 9:383. · 4.40 Impact Factor
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    ABSTRACT: The light, oxygen, or voltage (LOV) domain that belongs to the Per-ARNT-Sim (PAS) domain superfamily is a blue light sensory module. The Arabidopsis thaliana PAS/LOV PROTEIN (PLP) gene encodes three putative blue light receptor proteins, PLPA, PLPB, and PLPC, because of its mRNA splicing variation. PLPA and PLPB each contain one PAS domain at the N-terminal region and one LOV domain at the C-terminal region, while the LOV domain is truncated in PLPC. RNA gel blot analysis showed that PLP mRNA was markedly expressed after exposure to salt or dehydration stress. Yeast two-hybrid screening led to the isolation of VITAMIN C DEFECTIVE 2 (VTC2), VTC2-LIKE (VTC2L), and BEL1-LIKE HOMEODOMAIN 10 proteins (BLH10A and BLH10B) as PLP-interacting proteins. The molecular interaction of PLPA with VTC2L, BLH10A or BLH10B, and that of PLPB with VTC2L were diminished when yeasts were grown under blue light illumination. Furthermore, the possible binding of flavin chromophore to PLPA and PLPB was demonstrated. These results imply that the LOV domain of PLPA and PLPB functions as a blue light sensor, and suggest the applicability of these interactions to blue light-dependent switching in transcriptional regulation in yeast or other organisms.
    Journal of Plant Research 02/2008; 121(1):97-105. · 2.06 Impact Factor
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    ABSTRACT: Populus is one of favorable model plants because of its small genome. Structural genomics of Populus has reached a breakpoint as nucleotides of the entire genome have been determined. Reaching the post genome era, functional genomics of Populus is getting more important for well-comprehended plant science. Development of bioresorce serving functional genomics is making rapid progress. Huge efforts have achieved deposits of expressed sequence tags (ESTs) in various plant species consequently accelerating functional analysis of genes. ESTs from full-length cDNA clones are especially powerful for accurate molecular annotation. We promoted collection and annotation of the ESTs from Populus full-length enriched cDNA clones as part of functional genomics of tree species. We have been collecting the full-length enriched cDNA of the female poplar (Populus nigra var. italica) for years. By sequencing P. nigra full-length (PnFL) cDNA libraries, we generated about 116,000 5'-end or 3'-end ESTs corresponding to 19,841 nonredundant PnFL clones. Population of PnFL cDNA clones represents 44% of the predicted genes in the Populus genome. Our resource of P. nigra full-length enriched clones is expected to provide valuable tools to gain further insight into genome annotation and functional genomics in Populus.
    BMC Genomics 02/2007; 8:448. · 4.40 Impact Factor
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    ABSTRACT: Secondary metabolites called norlignans are produced in the xylem of Cryptomeria japonica D. Don. Several norlignans have roles in the defense of sapwood against microbial invasion and in the coloration of heartwood. The biosynthetic pathway of norlignans is largely unknown. Norlignans have been reported to accumulate in the sapwood during the drying of C. japonica logs. To search for genes encoding enzymes that catalyze the synthesis of norlignans, we carried out suppression subtractive hybridization using the fresh sapwood of a felled log and the drying sapwood in which a norlignan, agatharesinol, accumulated. A total of 1050 expressed sequence tags were obtained from the subtracted cDNA library, and these were assembled into 146 contigs and 361 singletons. Of these 507 unique sequences, 263 were functionally classified into 12 categories. "Metabolism" was the largest category, with 23% (61) of classified sequences. Twenty-six sequences that encode 16 enzymes were assigned to "secondary metabolism." Expression analysis of 15 genes related to "secondary metabolism" revealed that 12 of these genes had transcripts that were induced during the sapwood drying process. Of the 12 genes, 10 encoded enzymes that use aromatic compounds as substrates. In addition, 58 sequences representing 22 defense-related proteins were found. Our subtraction library should be a useful source for isolating genes encoding proteins involved in secondary metabolism including norlignan biosynthesis and defense in C. japonica xylem.
    Tree Physiology 02/2007; 27(1):1-9. · 2.85 Impact Factor
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    ABSTRACT: Poplar, whose genome is the first to be sequenced among woody plants, is a favorable model for plant biologists to enable them to understand molecular processes of growth, development and responses to environmental stimuli in trees. The sequence will allow the development of a strategy for improving environmental stress tolerance in forest trees. In this study, we have generated a full-length enriched cDNA library from leaves of axenically grown poplar (Populus nigra var. italica) subjected to environmental stress treatments by dehydration, high salinity, chilling, heat, abscisic acid (ABA) and H2O2. We sequenced >30,000 expressed sequence tags (ESTs) from the cDNA library and consequently collected approximately 4,500 non-redundant clones. We further analyzed cDNAs encoding an ERF/AP2-domain transcription factor which is specific in plants and plays an important role under stress. Thirteen candidates containing the ERF/AP2 domain were found within our EST resource. Some of them showed stress-responsive gene expression. We report here the first collection of full-length enriched stress-related ESTs of poplar and discuss environmental stress responses of forest trees in the light of comparative genomics.
    Plant and Cell Physiology 01/2005; 45(12):1738-48. · 4.13 Impact Factor
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    ABSTRACT: Arginine decarboxylase (ADC) catalyzes the first step of polyamine (PA) biosynthesis to produce putrescine (Put) from arginine (Arg). One of the 2 Arabidopsis ADC genes, AtADC2, is induced in response to salt stress causing the accumulation of free Put. To analyze the roles of stress-inducible AtADC2 gene and endogenous Put in stress tolerance, we isolated a Ds insertion mutant of AtADC2 gene (adc2-1) and characterized its phenotypes under salt stress. In the adc2-1 mutant, free Put content was reduced to about 25% of that in the control plants and did not increase under salt stress. Furthermore, the adc2-1 mutant was more sensitive to salt stress than the control plants. The stress sensitivity of adc2-1 was recovered by the addition of exogenous Put. These results indicate that endogenous Put plays an important role in salt tolerance in Arabidopsis. AtADC2 is a key gene for the production of Put under not only salinity conditions, but also normal conditions.
    Biochemical and Biophysical Research Communications 02/2004; 313(2):369-75. · 2.41 Impact Factor
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    ABSTRACT: Damage to Japanese cedars caused by the sugi bark borer in plots with low, medium and high planting density (1,700, 3,200, and 7,300 trees/ha, respectively) was examined in a 20-year-old sugi plantation. Radial growth and annual ring-width at breast height of three trees sampled per plot were measured by stem analysis. Stand age when each pupal chamber formed on the sample trees by the borer was also investigated by sawing the trees. There was less damage in the high density plot than in the low density plot. Radial growth at breast height increased rapidly from the 7th year after planting in all plots. The width of the annual ring reached a maximum in the 9th or 10th year, and decreased gradually thereafter. Radial growth in the low density plot was larger than that in the high density plot. Pupal chambers were first observed in the 7th year. The number of pupal chambers increased yearly, reaching a maximum in the 12th or 13th year, and decreased rapidly thereafter. These results indicate that restriction of radial growth of trees in the juvenile period by high density planting can prevent infestation of the sugi bark borer.In this study, we measured the positioning accuracy of the Global Positioning System (GPS) while walking in forested areas and analyzed the GPS data to find factors that affected the positioning accuracy. In the field tests, we repeated GPS measurements with different types of GPS receivers, types of forests and modes of GPS positioning. The GPS data were analyzed using ANOVA. As a result, the type of GPS receivers, type of forests and modes of GPS positioning were found to be a significant factor (P < 0.001) to determine positioning accuracy while any interactions between these factors were not. The result also showed that the GPS receiver with multipath rejection technology produced higher positioning accuracy than without it. Therefore, multipath errors, which are caused by the reflection of GPS signals due to nearby stems, can be a critical cause to adversely affect GPS positioning accuracy. It was also suggested that GPS positioning accuracy while walking in forested areas was affected not by basal area but by stand density. That was because temporal signal blocking occurred more often with increasing stand density while walking forested areas. As a result of multiple regression analysis, the observed Position Dilution of Precision (PDOP) was not a significant factor (P = 0.590) to determine positioning accuracy.Deciduous oak (Quercus serrata) forest is a major vegetation type of temperate broad-leaved forests in the north Kanto Region, Japan. The objective of this study is to examine the past and present human-use of the forests and to foresee the future prospects. The shiitake mushroom (Lentinus edodes) producing districts in Saitama and Tochigi were selected as the study areas. Until the 1960s more than 70% of local broad-leaved forests were used as fuelwood in the areas studied. After the revolutionary change in the forms of energy used in the 1960s, oak forests turned to being used mainly for shiitake cultivation in many rural areas. Most oak logs for shiitake have been provided within the shiitake-producing area, but in recent years the number of logs brought from other areas is increasing in fresh shiitake cultivation. Because of the rapid expansion of shiitake imports, aging of the domestic cultivators and labor shortage, domestic shiitake cultivation has declined conspicuously for the last 15 years. In addition, many forest owners and cultivators have already stopped managing the forests as they used to. As a result, if the shiitake cultivation continues to shrink, it is estimated that around 90% of the local broad-leaved forests will be abandoned by the year of 2,015 even in shiitake-producing areas.This paper describes our comparative study on forest policies in Japan, the United States, and Sweden (EU) to assess the policies of Japan for preventing global warming. The forest policies in these three countries were compared in terms of the process of policy-making, overview of policy execution, forest management, forest conservation and protection, conserved and reserve forests, urban forests, biomass utilization, forest studies and indirect slash tools, and policies for attaining the goal of the first period. The forest policies of Japan are characterized by the use of non-physical methods of CO2 absorption, such as cultivating sound forests, managing reserve forests, promoting the use of biomass, and educating people. The United States has substantial policies for physical methods for actively absorbing CO2, such as planting trees. However, the US has not been able to acquire sufficient funds for the policies, and the target absorption has not been attained. Sweden has tended to use non-physical methods and has substantial policies for promoting the certification system, assigning conservation areas, and promoting the use of biomass energy.Hydrological control of streamwater NO3 – concentrations was investigated in a weathered granitic headwater forest catchment. The catchment was divided into three parts: the stream channel area, the soil sedimentation area, and the hillslope area connected to the soil sedimentation area. The discharge rate of saturated throughflow within the hillslope and catchment and the groundwater levels in the soil sedimentation area were measured in tandem with the hydrochemical observations. At the points observed, the streamwater had the lowest NO3 – concentrations. The concentrations were low during baseflow conditions and increased with the discharge rate. Considering the water budget in the hillslope, about half of the total rainfall infiltrated into the bedrock. This bedrock groundwater was the dominant component of the baseflow, with low NO3 – concentrations, while groundwater in the soil sediment area with relatively high concentrations flowed into the stream during rainstorms. The dynamics of the streamwater NO3 – concentrations were strongly affected by the hydrological processes in the forest catchment. Especially, the baseflow NO3 – concentrations were kept low by the groundwater flow passing through the bedrock.The objective of this study is establishment of vegetative propagation of Japanese black pine (Pinus thunbergii). We examined the effect of defoliation, disbudding and shape of basal cut on the rooting ability of cuttings, and we tried to find an optimal method of propagation. Cuttings were made from terminal shoots of 1-year-old seedlings. As a result, 1) When 0–46% of the needles of cuttings were removed, those rooting percentages were steady between 54 and 62%. However, when needles were removed excessively, rooting ability decreased notably. Moreover, 46% needle removal cuttings had the longest root systems. 2) In the case of cuttings with a part or all their buds removed, the rooting percentage was greater than that of control cuttings. 3) On the examination of treatments of the cut end, rooting ability was better for diagonal shape than for horizontal shapes, but difference in the effect was insignificant. So the optimal method is to remove half of the needles or buds from cuttings and to cut end in a diagonal shape. However, as growth of cuttings from which buds had been removed was bad, a careful needs to be paid to disbudding for commercial production.Chlorophyll fluorescence methods have been used to evaluate the effects of environmental stresses on photosynthetic properties. Chlorophyll fluorescence can provide detailed information of photosystem II (PSII) photochemistry, which is vulnerable to environmental stresses such as strong light, low temperature, heat and drought. I reviewed photoinhibition of photosynthesis and discussed the mechanism to prevent photoinhibition in drought-acclimated leaves. As drought stress is often accompanied by strong light, a decline in photosynthesis caused by stomatal closure increases the risk of photoinhibition. Energy dissipation via electron flow would be an effective way to prevent photodamage as well as thermal energy dissipation in PSII antennae.When plants are illuminated by excess light, inhibition of photosynthesis occurs by harmful molecules generated by excess excitation energy. Photochemical efficiency is also decreased during the dissipation of excitation energy by protective mechanism. Inhibition of photosynthesis by low temperature results in a considerable excess of excitation energy leading to photodamage. Although evergreen woody plants are considered to be subjected to photoinhibition, they develop many photoprotective mechanisms against photoinhibition. In this review, I summarized the molecular aspects of photoinhibition and role of photoprotective mechanisms, and discus the ecophysiological meanings of photoprotections, especially xanthophyll cycle, water-water cycle, and photodynamic screen provided by the accumulation of pigments such as rhodoxanthin and anthocyanine observed in over-wintering woody plants.Acid fog is considered to have a large influence on tree physiology because it has a high concentration of air pollutants and is persistent in the atmosphere. Long-range transported pollutants contribute to acidification of fog in mountainous areas and therefore trees grown in these areas are thought to be affected by acid fog. The effects of acid fog using tree seedlings are well documented. From the results of these experimental studies, acid fog is known to induce visible injury, reduce the dry weight and photosynthesis systems, disintegrate the epicuticular wax, alter the nutrient status, and increase the sensitivity to other stresses, such as frost, wind and ozone. In addition, the extent of these effects is dependent on the pH and the components of acid fog and tree species. In this review, we summarize these reports and discuss further developments in research.Degraded lands abandoned after failures of agricultural development are widely distributed over tropical areas. – Environmental reforestation – in degraded lands is needed for the rehabilitation of regional environments. In this paper, I review properties of problem soils in tropical Asia and stress responses of tropical trees, and discuss the development of methods of environmental reforestation.Food shortage and environmental deterioration due to rapid growth of the global population are the most serious problems that face us human beings. Improvement of tolerance of plants to abiotic stresses such as drought, high salinity, low temperature, and heat is one of the promising approaches for the future of agriculture and environmental conservation. It is essential to know at first how plants respond to environmental stresses and which molecules are involved in stress tolerance. According to recent development in genomics in Arabidopsis, it has been shown that hundreds of genes are involved in stress response and/or stress tolerance. More recently, functional genomics in woody plants has been promoted mainly in the occident. A US group, in particular, is determining the nucleotide sequence of whole poplar genome, and this information will have been released by the end of the year 2003. We are convinced that the poplar will be more important as a model forest tree in the post-genome era. We here introduce the world-wide situation of genomics in the poplar and discuss a direction of study on stress physiology in woody plants.Genetic engineering has the potential to allow the selective improvement of individual traits in woody plants without the loss of any of the desired trait of the parental line. Using such techniques, we can overcome the difficulties associated with the breeding of long-lived perennials, which need to long time to produce progeny. In this paper, we introduce recent advances in the application of genetic engineering to forest trees to solve environmental problems. And, we also discuss the necessity of flowering control of transgenic woody plants.
    Journal of Forest Research 01/2004; 9(3):277-277. · 0.84 Impact Factor
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    ABSTRACT: To characterize the genes for enzymes involved in the biosynthesis of polyamines (PAs), their expression profiles were investigated and the levels of PAs in Arabidopsis thaliana quantified. In the Arabidopsis genome, eight genes involved in PAs biosynthesis were identified and the expression profiles of these genes were analysed, not only under abiotic stress to determine whether they were stress-inducible, constitutive, or stress-repressible, but also in various organs to show their tissue specificity. AtADC2 and AtSPMS mRNAs, encoding arginine decarboxylase and spermine synthase, clearly increased in response to NaCl and dehydration and abscisic acid treatments. Stress-inducible accumulation of AtADC2 mRNA correlated with putrescine (Put) accumulation under NaCl and dehydration treatments. In a cold condition, AtSAMDC2 mRNA increased significantly. AtADC2 and AtSAMDC2 mRNA were expressed in sexual organs such as flowers, buds and immature siliques. PAs also accumulated in sexual organs. These results suggest that the transcripts of eight genes involved in PA biosynthesis show different profiles of expression not only in response to environmental stress but also during plant development.
    Plant Cell and Environment 10/2003; 26(11):1917 - 1926. · 5.14 Impact Factor
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    ABSTRACT: Plants respond and adapt to drought stress in order to survive under stress conditions. Several genes that respond to drought at the transcriptional level have been described, but there are few reports on genes involved in the recovery from dehydration. Analysis of rehydration-inducible genes should help not only to understand the molecular mechanisms of stress responses in higher plants, but also to improve the stress tolerance of crops by gene manipulation. We used a full-length cDNA microarray containing ca. 7000 Arabidopsis full-length cDNAs and identified 152 rehydration-inducible genes. Venn diagram analysis showed relationship of the rehydration-inducible genes to proline-inducible and water-treatment-inducible genes. Among the 152 rehydration-inducible genes, 58 genes contained the ACTCAT sequence involved in proline- and hypoosmolarity-inducible gene expression in their promoter regions, suggesting that ACTCAT sequence is a major cis-acting element involved in rehydration-inducible gene expression, and that some novel cis-acting elements are involved in rehydration-inducible gene expression. Functional analysis of rehydration-inducible and rehydration-repressed genes revealed their functions not only in the release from a stressed status but also in the recovery of growth in plants.
    The Plant Journal 07/2003; 34(6):868-87. · 6.58 Impact Factor
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    ABSTRACT: The toxicity of proline (Pro) to plant growth has raised questions despite its protective functions in response to environmental stresses. To evaluate Pro toxicity, we isolated an Arabidopsis T-DNA-tagged mutant, pdh, that had a defect in Pro dehydrogenase (AtProDH), which catalyzes the first step of Pro catabolism. The pdh mutant showed hypersensitivity to exogenous application of < or =10 mM L-Pro, at which wild-type plants grew normally. A dose-dependent increase in internal free Pro accumulation was observed in pdh plants during external Pro supply. These results do not just prove the toxicity of Pro, but also suggest that AtProDH is the only enzyme acting as a functional ProDH in Arabidopsis: To further analyze the targets of Pro toxicity, we compared the expression of thousands of genes by pdh plants with that by wild-type plants by cDNA microarray analysis. Most genes were unaffected. Here we demonstrate Pro toxicity by using the pdh mutant and discuss a cause-and-effect action between an excess of free Pro and growth inhibition in Arabidopsis.
    Plant and Cell Physiology 05/2003; 44(5):541-8. · 4.13 Impact Factor
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    ABSTRACT: Full-length cDNAs are essential for functional analysis of plant genes. Recently, cDNA microarray analysis has been developed for quantitative analysis of global and simultaneous analysis of expression profiles. Microarray technology is a powerful tool for identifying genes induced by environmental stimuli or stress and for analyzing their expression profiles in response to environmental signals. We prepared an Arabidopsis full-length cDNA microarray containing around 7,000 independent full-length cDNA groups and analyzed the expression profiles of genes. The transcripts of 245, 299, 54 and 213 genes increased after abscisic acid (ABA), drought-, cold-, and salt-stress treatments, respectively, with inducibilities more than fivefold compared with those of control genes [corrected]. The cDNA microarray analysis showed that many ABA-inducible genes were induced after drought- and high-salinity-stress treatments, and that there is more crosstalk between drought and ABA responses than between ABA and cold responses. Among the ABA-inducible genes identified, we identified 22 transcription factor genes, suggesting that many transcriptional regulatory mechanisms exist in the ABA signal transduction pathways.
    Functional and Integrative Genomics 12/2002; 2(6):282-91. · 3.29 Impact Factor
  • Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme 10/2002; 47(12 Suppl):1684-9.
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    ABSTRACT: Full-length cDNAs are essential for functional analysis of plant genes in the post-sequencing era of the Arabidopsis genome. Recently, cDNA microarray analysis has been developed for quantitative analysis of global and simultaneous analysis of expression profiles. We have prepared a full-length cDNA microarray containing approximately 7000 independent, full-length cDNA groups to analyse the expression profiles of genes under drought, cold (low temperature) and high-salinity stress conditions over time. The transcripts of 53, 277 and 194 genes increased after cold, drought and high-salinity treatments, respectively, more than fivefold compared with the control genes. We also identified many highly drought-, cold- or high-salinity- stress-inducible genes. However, we observed strong relationships in the expression of these stress-responsive genes based on Venn diagram analysis, and found 22 stress-inducible genes that responded to all three stresses. Several gene groups showing different expression profiles were identified by analysis of their expression patterns during stress-responsive gene induction. The cold-inducible genes were classified into at least two gene groups from their expression profiles. DREB1A was included in a group whose expression peaked at 2 h after cold treatment. Among the drought, cold or high-salinity stress-inducible genes identified, we found 40 transcription factor genes (corresponding to approximately 11% of all stress-inducible genes identified), suggesting that various transcriptional regulatory mechanisms function in the drought, cold or high-salinity stress signal transduction pathways.
    The Plant Journal 09/2002; 31(3):279-92. · 6.58 Impact Factor
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    ABSTRACT: Many organisms, including higher plants, accumulate free proline (Pro) in response to osmotic stress. Although various studies have focused on the ability of Pro as a compatible osmolyte involved in osmotolerance, its specific role throughout plant growth is still unclear. It has been reported that Pro is synthesized from Glu catalyzed by a key enzyme, Δ1-pyrroline-5-carboxylate synthetase (P5CS), in plants. To elucidate essential roles of Pro, we generated antisense transgenic Arabidopsis plants with a P5CS cDNA. Several transgenics accumulated Pro at a significantly lower level than wild-type plants, providing direct evidence for a key role of P5CS in Pro production in Arabidopsis. These antisense transgenics showed morphological alterations in leaves and a defect in elongation of inflorescences. Furthermore, transgenic leaves were hypersensitive to osmotic stress. Microscopic analysis of transgenic leaves, in which the mutated phenotype clearly occurred, showed morphological abnormalities of epidermal and parenchymatous cells and retardation of differentiation of vascular systems. These phenotypes were suppressed by exogenous L-Pro but not by D-Pro or other Pro analogues. In addition, Pro deficiency did not broadly affect all proteins but specifically affected structural proteins of cell walls in the antisense transgenic plants. These results indicate that Pro is not just an osmoregulator in stressed plants but has a unique function involved in osmotolerance as well as in morphogenesis as a major constituent of cell wall structural proteins in plants.
    The Plant Journal 01/2002; 18(2):185 - 193. · 6.58 Impact Factor
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    ABSTRACT: From Arabidopsis thaliana we isolated four different cDNAs that encode extensins, a family of cell-wall hydroxyproline-rich glycoproteins (HRGPs). Putative proteins (AtExt2-5) contained one open reading frame and characteristic Ser-(Pro)4 sequences organized in a high-order repetitive motif. AtExt2-5 genes were strongly expressed during rehydration after dehydration. They were also expressed after treatment with various amino acids. In particular, AtExt3 and five mRNAs were abundantly accumulated after treatment with L-Ser, Hyp, and L-Pro, which are major components of extensin proteins. The AtExt transcripts were strongly expressed in root tissues of both unbolted and bolted plants. The transcripts of AtExt2, 3, and 5 were also detected in the lower stem and flower buds, and that of AtExt4 was detected in bolted flowers. Therefore, we suggest that these four AtExt genes are novel extensin genes in A. thaliana, because the expression of atExt1, which has already been isolated from A. thaliana, was different from these.
    DNA Research 07/2001; 8(3):115-22. · 4.43 Impact Factor
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    ABSTRACT: Synthesis, degradation, and transport of proline (Pro) are thought to cooperatively control its endogenous levels in higher plants in response to environmental conditions. To evaluate the function of Pro degradation in the regulation of the levels of Pro and to elucidate roles of Pro in stress tolerance, we generated antisense transgenic Arabidopsis plants with an AtProDH cDNA encoding proline dehydrogenase (ProDH), which catalyzes Pro degradation. Several transgenic lines accumulated Pro at higher levels than wild-type plants, providing evidence for a key role of ProDH in Pro degradation in Arabidopsis. These antisense transgenics were more tolerant to freezing and high salinity than wild-type plants, showing a positive correlation between Pro accumulation and stress tolerance in plants.
    FEBS Letters 12/1999; 461(3):205-10. · 3.58 Impact Factor
  • Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme 12/1999; 44(15 Suppl):2188-98.
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    ABSTRACT: Delta(1)-Pyrroline-5-carboxylate synthetase 1 (P5CS1) is the rate-limiting enzyme in the biosynthesis of proline by Arabidopsis thaliana. Results of Northern analysis using aba1, abi1, and abi3 mutants of A. thaliana suggest that the expression of the P5CS1 gene under water stress is induced via abscisic acid (ABA)-biosynthesis-dependent and -independent pathways. Expression via ABA biosynthesis does not require protein synthesis. Analysis using transgenic A. thaliana containing a P5CS1 promoter/GUS fused gene indicated that the P5CS1 gene of A. thaliana is expressed in the whole plant under dehydration and in reproductive organs and tissues (flower buds and surrounding parts, pollen and pistils, and young siliques in the early stage of seed formation) under unstressed conditions. Cis-acting elements involved in dehydration-responsive gene expression are shown to be located in a 117-bp region between positions -621 and -504 upstream from the transcriptional initiation site.
    Biochemical and Biophysical Research Communications 09/1999; 261(3):766-72. · 2.41 Impact Factor

Publication Stats

2k Citations
78.59 Total Impact Points

Institutions

  • 2004–2009
    • Forestry and Forest Products Research Institute
      • Department of Molecular and Cell Biology
      Kumamoto, Kumamoto Prefecture, Japan
  • 2003
    • University of Tsukuba
      • Institute of Biological Sciences
      Tsukuba, Ibaraki, Japan
  • 1999–2002
    • Tsukuba Medical Center Hospital
      Tsukuba, Ibaraki, Japan
  • 2001
    • Daiwa House Central Research Laboratory
      Edo, Tōkyō, Japan