Masanori Tamaoki
Research interests
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InterestsPlant Physiology, Abiotic Stress, Plant Biotechnology, Transgenic Plants, Plant Genetics
Publications
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2.68Impact points
High-throughput capture of nucleotide sequence polymorphisms in three Brassica species (Brassicaceae) using DNA microarrays.
American journal of botany. 03/2012; 99(3):e94-6.
• Premise of the study: To capture molecular markers that are applicable to environmental risk assessment of genetically modified oilseed rape, and to streamline their development, we screened variations in nucleotide sequences of three Brassica species by DNA microarray analysis. • Methods and Resu... [more] • Premise of the study: To capture molecular markers that are applicable to environmental risk assessment of genetically modified oilseed rape, and to streamline their development, we screened variations in nucleotide sequences of three Brassica species by DNA microarray analysis. • Methods and Results: Using the Affymetrix GeneChip Arabidopsis ATH1 Genome Array, we monitored gene expression at 22810 loci among the Brassica species and picked out 192 putative polymorphic loci. We sequenced 25 of these and successfully aligned them among all three species. All 25 loci possessed some interspecific and at times intraspecific nucleotide variation. • Conclusions: DNA microarray analysis effectively detected a large number of nucleotide sequence variations among closely related Brassica species. The polymorphic regions will allow the subsequent development of functional gene markers.
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3.59Impact points
The integral membrane protein SEN1 is required for symbiotic nitrogen fixation in Lotus japonicus nodules.
Plant & cell physiology. 11/2011; 53(1):225-36.
Legume plants establish a symbiotic association with bacteria called rhizobia, resulting in the formation of nitrogen-fixing root nodules. A Lotus japonicus symbiotic mutant, sen1, forms nodules that are infected by rhizobia but that do not fix nitrogen. Here, we report molecular identification of t... [more] Legume plants establish a symbiotic association with bacteria called rhizobia, resulting in the formation of nitrogen-fixing root nodules. A Lotus japonicus symbiotic mutant, sen1, forms nodules that are infected by rhizobia but that do not fix nitrogen. Here, we report molecular identification of the causal gene, SEN1, by map-based cloning. The SEN1 gene encodes an integral membrane protein homologous to Glycine max nodulin-21, and also to CCC1, a vacuolar iron/manganese transporter of Saccharomyces cerevisiae, and VIT1, a vacuolar iron transporter of Arabidopsis thaliana. Expression of the SEN1 gene was detected exclusively in nodule-infected cells and increased during nodule development. Nif gene expression as well as the presence of nitrogenase proteins was detected in rhizobia from sen1 nodules, although the levels of expression were low compared with those from wild-type nodules. Microscopic observations revealed that symbiosome and/or bacteroid differentiation are impaired in the sen1 nodules even at a very early stage of nodule development. Phylogenetic analysis indicated that SEN1 belongs to a protein clade specific to legumes. These results indicate that SEN1 is essential for nitrogen fixation activity and symbiosome/bacteroid differentiation in legume nodules.
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Seeds of a Possible Natural Hybrid between Herbicide-Resistant Brassica napus and Brassica rapa Detected on a Riverbank in Japan.
GM crops. 06/2011; 2(3):201-10.
Transgenic herbicide-resistant varieties of Brassica napus, or oilseed rape, from which canola oil is obtained, are imported into Japan, where this plant is not commercially cultivated to a large extent. This study aimed to examine the distribution of herbicide-resistant B. napus and transgene flow ... [more] Transgenic herbicide-resistant varieties of Brassica napus, or oilseed rape, from which canola oil is obtained, are imported into Japan, where this plant is not commercially cultivated to a large extent. This study aimed to examine the distribution of herbicide-resistant B. napus and transgene flow to escaped populations of its closely related species, B. rapa and B. juncea. Samples were collected from 12 areas near major ports through which oilseed rape imports into Japan passed-Kashima, Chiba, Yokohama, Shimizu, Nagoya, Yokkaichi, Sakai-Senboku, Kobe, Uno, Mizushima, Kita-Kyushu, and Hakata-and the presence of glyphosate- and/or glufosinate-resistant B. napus was confirmed in all areas except Yokohama, Sakai-Senboku, Uno, and Kita-Kyushu. The Yokkaichi area was the focus because several herbicide-resistant B. napus plants were detected not only on the roadside where oilseed rape spilled during transportation but also on the riverbanks, where escaped populations of B. rapa and B. juncea grew. Samples of B. napus that were tolerant to both herbicides were detected in four continuous years (2005-2008) in this area, suggesting the possibility of intraspecific transgene flow within the escaped B. napus populations. Moreover, in 2008, seeds of a possible natural hybrid between herbicide-tolerant B. napus (2n = 38) and B. rapa (2n = 20) were detected; some seedlings derived from the seeds collected at a Yokkaichi site showed glyphosate resistance and had 2n = 29 chromosomes. This observation strongly suggests the occurrence of hybridization between herbicide-resistant B. napus and escaped B. rapa and the probability of introgression of a herbicide-resistance gene into related escaped species.
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1.52Impact points
Expression and functions of myo-inositol monophosphatase family genes in seed development of Arabidopsis.
Journal of plant research. 10/2010; 124(3):385-94.
Myo-inositol monophosphatase (IMP) catalyzes the dephosphorylation of myo-inositol 3-phosphate in the last step of myo-inositol biosynthesis. IMP is also important in phosphate metabolism and is required for the biosynthesis of cell wall polysaccharides, phytic acid, and phosphatidylinositol. In Ara... [more] Myo-inositol monophosphatase (IMP) catalyzes the dephosphorylation of myo-inositol 3-phosphate in the last step of myo-inositol biosynthesis. IMP is also important in phosphate metabolism and is required for the biosynthesis of cell wall polysaccharides, phytic acid, and phosphatidylinositol. In Arabidopsis, IMP is encoded by VTC4. There are, however, two additional IMP candidate genes, IMPL1 and IMPL2, which have not yet been elucidated. In our genetic studies of Arabidopsis IMP genes, only the loss-of-function mutant impl2 showed embryonic lethality at the globular stage. All IMP genes were expressed in a similar manner both in the vegetative and reproductive organs. In developing seeds, expression of IMP genes was not coupled with the expression of the genes encoding myo-inositol phosphate synthases, which supply the substrate for IMPs in the de novo synthesis pathway. Instead, expression of IMP genes was correlated with expression of the gene for myo-inositol polyphosphate 1-phosphatase (SAL1), which is involved in the myo-inositol salvage pathway, suggesting a possible salvage pathway role in seed development. Moreover, the partial rescue of the impl2 phenotype by histidine application implies that IMPL2 is also involved in histidine biosynthesis during embryo development.
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Rapeseed species and environmental concerns related to loss of seeds of genetically modified oilseed rape in Japan.
GM crops. 05/2010; 1(3):143-56.
Feral rapeseed in Japan consists of Brassica rapa, B. juncea and B. napus, mostly produced by escape from crops. Brassica rapa and B. juncea were introduced from abroad long ago as leaf and root vegetables and as an oil crop and breeders have developed various cultivars. Brassica napus was introduce... [more] Feral rapeseed in Japan consists of Brassica rapa, B. juncea and B. napus, mostly produced by escape from crops. Brassica rapa and B. juncea were introduced from abroad long ago as leaf and root vegetables and as an oil crop and breeders have developed various cultivars. Brassica napus was introduced in the late 1800s, mainly as an oil crop. Rapeseed production in Japan is low, and most demand is met by imports from Canada (94.4% of the 2009 trade volume). Recently, spontaneous B. napus, including genetically modified (GM) herbicide-resistant individuals, has been detected along Japanese roads, probably originating from seeds lost during transportation of imports. As GM oilseed production increases abroad, the probability of escape of GM oilseed rape in Japan will increase, raising environmental biosafety concerns related to the impact of feral rapeseed on heirloom brassicaceous crops. In this paper, we review the history of rapeseed introduction in Japan and future concerns.
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6.24Impact points
Molecular mechanisms of selenium tolerance and hyperaccumulation in Stanleya pinnata.
Plant physiology. 05/2010; 153(4):1630-52.
The molecular mechanisms responsible for selenium (Se) tolerance and hyperaccumulation were studied in the Se hyperaccumulator Stanleya pinnata (Brassicaceae) by comparing it with the related secondary Se accumulator Stanleya albescens using a combination of physiological, structural, genomic, and b... [more] The molecular mechanisms responsible for selenium (Se) tolerance and hyperaccumulation were studied in the Se hyperaccumulator Stanleya pinnata (Brassicaceae) by comparing it with the related secondary Se accumulator Stanleya albescens using a combination of physiological, structural, genomic, and biochemical approaches. S. pinnata accumulated 3.6-fold more Se and was tolerant to 20 microm selenate, while S. albescens suffered reduced growth, chlorosis and necrosis, impaired photosynthesis, and high levels of reactive oxygen species. Levels of ascorbic acid, glutathione, total sulfur, and nonprotein thiols were higher in S. pinnata, suggesting that Se tolerance may in part be due to increased antioxidants and up-regulated sulfur assimilation. S. pinnata had higher selenocysteine methyltransferase protein levels and, judged from liquid chromatography-mass spectrometry, mainly accumulated the free amino acid methylselenocysteine, while S. albescens accumulated mainly the free amino acid selenocystathionine. S. albescens leaf x-ray absorption near-edge structure scans mainly detected a carbon-Se-carbon compound (presumably selenocystathionine) in addition to some selenocysteine and selenate. Thus, S. albescens may accumulate more toxic forms of Se in its leaves than S. pinnata. The species also showed different leaf Se sequestration patterns: while S. albescens showed a diffuse pattern, S. pinnata sequestered Se in localized epidermal cell clusters along leaf margins and tips, concentrated inside of epidermal cells. Transcript analyses of S. pinnata showed a constitutively higher expression of genes involved in sulfur assimilation, antioxidant activities, defense, and response to (methyl)jasmonic acid, salicylic acid, or ethylene. The levels of some of these hormones were constitutively elevated in S. pinnata compared with S. albescens, and leaf Se accumulation was slightly enhanced in both species when these hormones were supplied. Thus, defense-related phytohormones may play an important signaling role in the Se hyperaccumulation of S. pinnata, perhaps by constitutively up-regulating sulfur/Se assimilation followed by methylation of selenocysteine and the targeted sequestration of methylselenocysteine.
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1.52Impact points
DEAR1, a transcriptional repressor of DREB protein that mediates plant defense and freezing stress responses in Arabidopsis.
Journal of plant research. 08/2009;
Plants have evolved intricate mechanisms to respond and adapt to a wide variety of biotic and abiotic stresses in their environment. The Arabidopsis DEAR1 (DREB and EAR motif protein 1; At3g50260) gene encodes a protein containing significant homology to the DREB1/CBF (dehydration-responsive element... [more] Plants have evolved intricate mechanisms to respond and adapt to a wide variety of biotic and abiotic stresses in their environment. The Arabidopsis DEAR1 (DREB and EAR motif protein 1; At3g50260) gene encodes a protein containing significant homology to the DREB1/CBF (dehydration-responsive element binding protein 1/C-repeat binding factor) domain and the EAR (ethylene response factor-associated amphiphilic repression) motif. We show here that DEAR1 mRNA accumulates in response to both pathogen infection and cold treatment. Transgenic Arabidopsis overexpressing DEAR1 (DEAR1ox) showed a dwarf phenotype and lesion-like cell death, together with constitutive expression of PR genes and accumulation of salicylic acid. DEAR1ox also showed more limited P. syringae pathogen growth compared to wild-type, consistent with an activated defense phenotype. In addition, transient expression experiments revealed that the DEAR1 protein represses DRE/CRT (dehydration-responsive element/C-repeat)-dependent transcription, which is regulated by low temperature. Furthermore, the induction of DREB1/CBF family genes by cold treatment was suppressed in DEAR1ox, leading to a reduction in freezing tolerance. These results suggest that DEAR1 has an upstream regulatory role in mediating crosstalk between signaling pathways for biotic and abiotic stress responses.
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2.71Impact points
Ethylene and salicylic acid control glutathione biosynthesis in ozone-exposed Arabidopsis thaliana.
Physiologia plantarum. 03/2009;
Ozone produces reactive oxygen species and induces the synthesis of phytohormones, including ethylene and salicylic acid. These phytohormones act as signal molecules that enhance cell death in response to ozone exposure. However, some studies have shown that ethylene and salicylic acid can instead d... [more] Ozone produces reactive oxygen species and induces the synthesis of phytohormones, including ethylene and salicylic acid. These phytohormones act as signal molecules that enhance cell death in response to ozone exposure. However, some studies have shown that ethylene and salicylic acid can instead decrease the magnitude of ozone-induced cell death. Therefore, we studied the defensive roles of ethylene and salicylic acid against ozone. Unlike the wild-type, Col-0, Arabidopsis mutants deficient in ethylene signaling (ein2) or salicylic acid biosynthesis (sid2) generated high levels of superoxide and exhibited visible leaf injury, indicating that ethylene and salicylic acid can reduce ozone damage. Macroarray analysis suggested that the ethylene and salicylic acid defects influenced glutathione (GSH) metabolism. Increases in the reduced form of GSH occurred in Col-0 6 h after ozone exposure, but little GSH was detected in ein2 and sid2 mutants, suggesting that GSH levels were affected by ethylene or salicylic acid signaling. We performed gene expression analysis by real-time polymerase chain reaction using genes involved in GSH metabolism. Induction of gamma-glutamylcysteine synthetase (GSH1), glutathione synthetase (GSH2), and glutathione reductase 1 (GR1) expression occurred normally in Col-0, but at much lower levels in ein2 and sid2. Enzymatic activities of GSH1 and GSH2 in ein2 and sid2 were significantly lower than in Col-0. Moreover, ozone-induced leaf damage observed in ein2 and sid2 was mitigated by artificial elevation of GSH content. Our results suggest that ethylene and salicylic acid protect against ozone-induced leaf injury by increasing de novo biosynthesis of GSH.
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New insights into the roles of ethylene and jasmonic acid in the acquisition of selenium resistance in plants.
Plant signaling & behavior. 11/2008; 3(10):865-7.
In a recent paper, we reported that both ethylene and jasmonic acid (JA) are important for selenium (Se) resistance in Arabidopsis.1 Elevated levels of reactive oxygen species were associated with ethylene and JA production in a Se-resistant Arabidopsis ecotype. Here, we further discuss the function... [more] In a recent paper, we reported that both ethylene and jasmonic acid (JA) are important for selenium (Se) resistance in Arabidopsis.1 Elevated levels of reactive oxygen species were associated with ethylene and JA production in a Se-resistant Arabidopsis ecotype. Here, we further discuss the functions of these phytohormones, and their possible interactions, in plant Se resistance and -accumulation, placing our data in a broader perspective of other recently published papers.
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3.37Impact points
An unidentified ultraviolet-B-specific photoreceptor mediates transcriptional activation of the cyclobutane pyrimidine dimer photolyase gene in plants.
Planta. 10/2008;
Cyclobutane pyrimidine dimers (CPDs) constitute a majority of DNA lesions caused by ultraviolet-B (UVB). CPD photolyase, which rapidly repairs CPDs, is essential for plant survival under sunlight containing UVB. Our earlier results that the transcription of the cucumber CPD photolyase gene (CsPHR) w... [more] Cyclobutane pyrimidine dimers (CPDs) constitute a majority of DNA lesions caused by ultraviolet-B (UVB). CPD photolyase, which rapidly repairs CPDs, is essential for plant survival under sunlight containing UVB. Our earlier results that the transcription of the cucumber CPD photolyase gene (CsPHR) was activated by light have prompted us to propose that this light-driven transcriptional activation would allow plants to meet the need of the photolyase activity upon challenges of UVB from sunlight. However, molecular mechanisms underlying the light-dependent transcriptional activation of CsPHR were unknown. In order to understand spectroscopic aspects of the plant response, we investigated the wavelength-dependence (action spectra) of the light-dependent transcriptional activation of CsPHR. In both cucumber seedlings and transgenic Arabidopsis seedlings expressing reporter genes under the control of the CsPHR promoter, the action spectra exhibited the most predominant peak in the long-wavelength UVB waveband (around 310 nm). In addition, a 95-bp cis-acting region in the CsPHR promoter was identified to be essential for the UVB-driven transcriptional activation of CsPHR. Thus, we concluded that the photoperception of long-wavelength UVB by UVB photoreceptor(s) led to the induction of the CsPHR transcription via a conserved cis-acting element.
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6.95Impact points
The Arabidopsis sweetie mutant is affected in carbohydrate metabolism and defective in the control of growth, development and senescence.
The Plant journal : for cell and molecular biology. 05/2008;
Sugars modulate many vital metabolic and developmental processes in plants, from seed germination to flowering, senescence and protection against diverse abiotic and biotic stresses. However, the exact mechanisms involved in morphogenesis, developmental signalling and stress tolerance remain largely... [more] Sugars modulate many vital metabolic and developmental processes in plants, from seed germination to flowering, senescence and protection against diverse abiotic and biotic stresses. However, the exact mechanisms involved in morphogenesis, developmental signalling and stress tolerance remain largely unknown. Here we report the characterization of a novel Arabidopsis thaliana mutant, sweetie, with drastically altered morphogenesis, and a strongly modified carbohydrate metabolism leading to elevated levels of trehalose, trehalose-6-phosphate and starch. We additionally show that the disruption of SWEETIE causes significant growth and developmental alterations, such as severe dwarfism, lancet-shaped leaves, early senescence and flower sterility. Genes implicated in sugar metabolism, senescence, ethylene biosynthesis and abiotic stress were found to be upregulated in sweetie. Our physiological, biochemical, genetic and molecular data indicate that the mutation in sweetie was nuclear, single and recessive. The effects of metabolizable sugars and osmolytes on sweetie morphogenesis were distinct; in light, sweetie was hypersensitive to sucrose and glucose during vegetative growth and a partial phenotypic reversion took place in the presence of high sorbitol concentrations. However, SWEETIE encodes a protein that is unrelated to any known enzyme involved in sugar metabolism. We suggest that SWEETIE plays an important regulatory function that influences multiple metabolic, hormonal and stress-related pathways, leading to altered gene expression and pronounced changes in the accumulation of sugar, starch and ethylene.
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6.24Impact points
Cooperative ethylene and jasmonic acid signaling regulates selenite resistance in Arabidopsis.
Plant physiology. 04/2008; 146(3):1219-30.
Selenium (Se) is an essential element for many organisms, but excess Se is toxic. To better understand plant Se toxicity and resistance mechanisms, we compared the physiological and molecular responses of two Arabidopsis (Arabidopsis thaliana) accessions, Columbia (Col)-0 and Wassilewskija (Ws)-2, t... [more] Selenium (Se) is an essential element for many organisms, but excess Se is toxic. To better understand plant Se toxicity and resistance mechanisms, we compared the physiological and molecular responses of two Arabidopsis (Arabidopsis thaliana) accessions, Columbia (Col)-0 and Wassilewskija (Ws)-2, to selenite treatment. Measurement of root length Se tolerance index demonstrated a clear difference between selenite-resistant Col-0 and selenite-sensitive Ws-2. Macroarray analysis showed more pronounced selenite-induced increases in mRNA levels of ethylene- or jasmonic acid (JA)-biosynthesis and -inducible genes in Col-0 than in Ws-2. Indeed, Col-0 exhibited higher levels of ethylene and JA. The selenite-sensitive phenotype of Ws-2 was attenuated by treatment with ethylene precursor or methyl jasmonate (MeJA). Conversely, the selenite resistance of Col-0 was reduced in mutants impaired in ethylene or JA biosynthesis or signaling. Genes encoding sulfur (S) transporters and S assimilation enzymes were up-regulated by selenite in Col-0 but not Ws-2. Accordingly, Col-0 contained higher levels of total S and Se and of nonprotein thiols than Ws-2. Glutathione redox status was reduced by selenite in Ws-2 but not in Col-0. Furthermore, the generation of reactive oxygen species by selenite was higher in Col-0 than in Ws-2. Together, these results indicate that JA and ethylene play important roles in Se resistance in Arabidopsis. Reactive oxygen species may also have a signaling role, and the resistance mechanism appears to involve enhanced S uptake and reduction.
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The role of phytohormone signaling in ozone-induced cell death in plants.
Plant signaling & behavior. 04/2008; 3(3):166-74.
Ozone is the main photochemical oxidant that causes leaf damage in many plant species, and can thereby significantly decrease the productivity of crops and forests. When ozone is incorporated into plants, it produces reactive oxygen species (ROS), such as superoxide radicals and hydrogen peroxide. T... [more] Ozone is the main photochemical oxidant that causes leaf damage in many plant species, and can thereby significantly decrease the productivity of crops and forests. When ozone is incorporated into plants, it produces reactive oxygen species (ROS), such as superoxide radicals and hydrogen peroxide. These ROS induce the synthesis of several plant hormones, such as ethylene, salicylic acid, and jasmonic acid. These phytohormones are required for plant growth, development, and defense responses, and regulate the extent of leaf injury in ozone-fumigated plants. Recently, responses to ozone have been studied using genetically modified plants and mutants with altered hormone levels or signaling pathways. These researches have clarified the roles of phytohormones and the complexity of their signaling pathways. The present paper reviews the biosynthesis of the phytohormones ethylene, salicylic acid, and jasmonic acid, their roles in plant responses to ozone, and multiple interactions between these phytohormones in ozone-exposed plants.
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2.71Impact points
Transcriptome analyses give insights into selenium-stress responses and selenium tolerance mechanisms in Arabidopsis.
Physiologia plantarum. 03/2008; 132(2):236-53.
Selenate is chemically similar to sulfate and can be taken up and assimilated by plants via the same transporters and enzymes. In contrast to many other organisms, selenium (Se) has not been shown to be essential for higher plants. In excess, Se is toxic and restricts development. Both Se deficiency... [more] Selenate is chemically similar to sulfate and can be taken up and assimilated by plants via the same transporters and enzymes. In contrast to many other organisms, selenium (Se) has not been shown to be essential for higher plants. In excess, Se is toxic and restricts development. Both Se deficiency and toxicity pose problems worldwide. To obtain better insights into the effects of Se on plant metabolism and into plant mechanisms involved in Se tolerance, the transcriptome of Arabidopsis plants grown with or without selenate was studied and Se-responsive genes identified. Roots and shoots exhibited different Se-related changes in gene regulation and metabolism. Many genes involved in sulfur (S) uptake and assimilation were upregulated. Accordingly, Se treatment enhanced sulfate levels in plants, but the quantity of organic S metabolites decreased. Transcripts regulating the synthesis and signaling of ethylene and jasmonic acid were also upregulated by Se. Arabidopsis mutants defective in ethylene or jasmonate response pathways exhibited reduced tolerance to Se, suggesting an important role for these two stress hormones in Se tolerance. Selenate upregulated a variety of transcripts that were also reportedly induced by salt and osmotic stress. Selenate appeared to repress plant development, as suggested by the downregulation of genes involved in cell wall synthesis and auxin-regulated proteins. The Se-responsive genes discovered in this study may help create plants that can better tolerate and accumulate Se, which may enhance the effectiveness of Se phytoremediation or serve as Se-fortified food.
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2.58Impact points
SAZ, a new SUPERMAN-like protein, negatively regulates a subset of ABA-responsive genes in Arabidopsis.
Molecular genetics and genomics : MGG. 03/2008; 279(2):183-92.
Arabidopsis SUPERMAN (SUP) and members of its family are plant-unique C(2)H(2)-type zinc finger genes that have been implicated in plant growth and development. In this paper, we report that a new SUP-family gene, designated as S A- and A BA-downregulated z inc finger gene (SAZ), is involved in the ... [more] Arabidopsis SUPERMAN (SUP) and members of its family are plant-unique C(2)H(2)-type zinc finger genes that have been implicated in plant growth and development. In this paper, we report that a new SUP-family gene, designated as S A- and A BA-downregulated z inc finger gene (SAZ), is involved in the negative regulation of ABA-mediated signaling. SAZ-GUS fusion proteins were predominantly localized in the nuclei when they were transiently expressed in onion epidermal cells. SAZ transcripts were expressed in the leaves and pistils of very young flower buds. In young seedlings, SAZ expression was downregulated in response to environmental stresses such as drought, salt, ozone and ultraviolet-B irradiation. This downregulation was also observed in response to the phytohormones salicylic acid (SA) and abscisic acid (ABA). SA-responsive downregulation of SAZ was not observed in the npr1-1 mutant, indicating that this regulation is NPR1 dependent. RNAi-mediated knockdown of SAZ (SAZ-kd) resulted in elevated expression of the drought- and ABA-responsive genes rd29B and rab18 under unstressed conditions, and it enhanced the response of these genes to drought and ABA treatment. The expression of several other drought- and/or ABA-responsive genes was not affected by SAZ-kd. Based on these results, we propose that SAZ plays a role in repressing a subset of the ABA-mediated stress-responsive genes in unstressed conditions.
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3.59Impact points
Disruption of a gene encoding C4-dicarboxylate transporter-like protein increases ozone sensitivity through deregulation of the stomatal response in Arabidopsis thaliana.
Plant & cell physiology. 02/2008; 49(1):2-10.
To understand better the plant response to ozone, we isolated and characterized an ozone-sensitive (ozs1) mutant strain from a set of T-DNA-tagged Arabidopsis thaliana ecotype Columbia. The mutant plants show enhanced sensitivity to ozone, desiccation and sulfur dioxide, but have normal sensitivity ... [more] To understand better the plant response to ozone, we isolated and characterized an ozone-sensitive (ozs1) mutant strain from a set of T-DNA-tagged Arabidopsis thaliana ecotype Columbia. The mutant plants show enhanced sensitivity to ozone, desiccation and sulfur dioxide, but have normal sensitivity to hydrogen peroxide, low temperature and high light levels. The T-DNA was inserted at a single locus which is linked to ozone sensitivity. Identification of the genomic sequences flanking the T-DNA insertion revealed disruption of a gene encoding a transporter-like protein of the tellurite resistance/C(4)-dicarboxylate transporter family. Plants with either of two different T-DNA insertions in this gene were also sensitive to ozone, and these plants failed to complement ozs1. Transpiration levels, stomatal conductance levels and the size of stomatal apertures were greater in ozs1 mutant plants than in the wild type. The stomatal apertures of ozs1 mutant plants responded to light fluctuations but were always larger than those of the wild-type plants under the same conditions. The stomata of the mutant and wild-type plants responded similarly to stimuli such as light, abscisic acid, high concentrations of carbon dioxide and ozone. These results suggest that OZS1 helps to close stomata, being not involved in the responses to these signals.
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1.73Impact points
Complete genomic structure of the bloom-forming toxic cyanobacterium Microcystis aeruginosa NIES-843.
DNA research : an international journal for rapid publication of reports on genes and genomes. 01/2008; 14(6):247-56.
The nucleotide sequence of the complete genome of a cyanobacterium, Microcystis aeruginosa NIES-843, was determined. The genome of M. aeruginosa is a single, circular chromosome of 5,842,795 base pairs (bp) in length, with an average GC content of 42.3%. The chromosome comprises 6312 putative protei... [more] The nucleotide sequence of the complete genome of a cyanobacterium, Microcystis aeruginosa NIES-843, was determined. The genome of M. aeruginosa is a single, circular chromosome of 5,842,795 base pairs (bp) in length, with an average GC content of 42.3%. The chromosome comprises 6312 putative protein-encoding genes, two sets of rRNA genes, 42 tRNA genes representing 41 tRNA species, and genes for tmRNA, the B subunit of RNase P, SRP RNA, and 6Sa RNA. Forty-five percent of the putative protein-encoding sequences showed sequence similarity to genes of known function, 32% were similar to hypothetical genes, and the remaining 23% had no apparent similarity to reported genes. A total of 688 kb of the genome, equivalent to 11.8% of the entire genome, were composed of both insertion sequences and miniature inverted-repeat transposable elements. This is indicative of a plasticity of the M. aeruginosa genome, through a mechanism that involves homologous recombination mediated by repetitive DNA elements. In addition to known gene clusters related to the synthesis of microcystin and cyanopeptolin, novel gene clusters that may be involved in the synthesis and modification of toxic small polypeptides were identified. Compared with other cyanobacteria, a relatively small number of genes for two component systems and a large number of genes for restriction-modification systems were notable characteristics of the M. aeruginosa genome.
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Isolation of O3-response genes from Arabidopsis thaliana using cDNA macroarray.
Methods in molecular biology (Clifton, N.J.). 01/2008; 410:29-42.
Nylon membrane-based cDNA macroarrays are a widely available alternative to cDNA microarrays for the collection of large-scale gene expression data. cDNA macroarrays are used in many areas of molecular biology research for applications ranging from gene discovery to gene expression profiling. Althou... [more] Nylon membrane-based cDNA macroarrays are a widely available alternative to cDNA microarrays for the collection of large-scale gene expression data. cDNA macroarrays are used in many areas of molecular biology research for applications ranging from gene discovery to gene expression profiling. Although degree of location of DNA spot in cDNA macroarray is lower than that in cDNA microarray, it can be used to detect expression of a large number of genes because it uses radiolabeled cDNA as a probe. Thus, cDNA macroarray technology can be applied to obtain the gene expression profile in organs that show wide variety in mRNA expression, such as meristems in plant species and brain tissue. To carry out hybridization experiments with a cDNA macroarray, I describe here how to prepare macroarray filters on a small or large scale, as well as how to analyze macroarray experiments and determine the statistical significance of the gene expression data obtained.
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3.25Impact points
Glycosylation of bisphenol A by freshwater microalgae.
Chemosphere. 11/2007; 69(6):934-41.
The endocrine disruptor bisphenol A (BPA, 4,4'-isopropylidenediphenol) is used to manufacture polycarbonate plastic and epoxy resin linings of food and beverage cans, and the residues from these products are then sometimes discharged into rivers and lakes in waste leachates. However, the fate of... [more] The endocrine disruptor bisphenol A (BPA, 4,4'-isopropylidenediphenol) is used to manufacture polycarbonate plastic and epoxy resin linings of food and beverage cans, and the residues from these products are then sometimes discharged into rivers and lakes in waste leachates. However, the fate of BPA in the environment has not yet been thoroughly elucidated. Considering the effect of BPA on aquatic organisms, it is important that we estimate the concentration of BPA and its metabolites in the aquatic environment, but there are few data on the metabolites of BPA. Here, we focused on freshwater microalgae as organisms that contribute to the biodegradation or biotransformation of BPA in aquatic environments. When we added BPA to cultures of eight species of freshwater microalgae, a reduction in the concentration of BPA in the culture medium was observed in all cultures. BPA was metabolized to BPA glycosides by Pseudokirchneriella subcapitata, Scenedesmus acutus, Scenedesmus quadricauda, and Coelastrum reticulatum, and these metabolites were then released into the culture medium. The metabolite from P. subcapitata, S. acutus, and C. reticulatum was identified by FAB-MS and (1)H-NMR as bisphenol A-mono-O-beta-d-glucopyranoside (BPAGlc), and another metabolite, from S. quadricauda, was identified as bisphenol A-mono-O-beta-d-galactopyranoside (BPAGal). These results demonstrate that freshwater microalgae that inhabit universal environments can metabolize BPA to its glycosides. Because BPA glycosides accumulate in plants and algae, and may be digested to BPA by beta-glycosidase in animal intestines, more attention should be given to levels of BPA glycosides in the environment to estimate the ecological impact of discharged BPA.
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3.37Impact points
The isochorismate pathway is negatively regulated by salicylic acid signaling in O3-exposed Arabidopsis.
Planta. 11/2007; 226(5):1277-85.
Ozone (O3), a major photochemical oxidant, causes leaf injury in plants. Plants synthesize salicylic acid (SA), which is reported to greatly affect O3 sensitivity. However, the mechanism of SA biosynthesis under O3 exposure remains unclear. Plants synthesize SA either by a pathway involving phenylal... [more] Ozone (O3), a major photochemical oxidant, causes leaf injury in plants. Plants synthesize salicylic acid (SA), which is reported to greatly affect O3 sensitivity. However, the mechanism of SA biosynthesis under O3 exposure remains unclear. Plants synthesize SA either by a pathway involving phenylalanine as a substrate or another involving isochorismate. To clarify how SA is produced in O3-exposed Arabidopsis, we examined the activities of phenylalanine ammonia lyase (PAL) and isochorismate synthase (ICS), which are components of the phenylalanine and isochorismate pathways, respectively. Exposure of Arabidopsis to O3 enhanced the accumulation of SA and the increase of ICS activity but did not affect PAL activity. In sid2 mutants, which have a defect in ICS1, the level of SA and the activity of ICS did not increase in response to O3 exposure. These results suggest that SA is mainly synthesized from isochorismate in Arabidopsis. Furthermore, the level of ICS1 expression and the activity of ICS during O3 exposure elevated in plants deficient for SA signaling (npr1 and eds5 mutants and NahG transgenics). Treatment of plants with SA also suppressed the enhancement of ICS1 expression by O3. These results suggest that SA synthesis is negatively regulated by SA signaling.
Following (9)
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Premendra Dwivedi
Indian Institute of Toxicology Research -
Michèle Boitel-Conti
Université de Picardie Jules Verne -
Ganesh Kumar Agrawal
Research laboratory for Biotechnology and Biochemistry (RLABB) -
Minami Matsui
RIKEN, Japan -
Jutarou Fukazawa
Hiroshima University
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