Hikaru Saji - Academia.edu (original) (raw)
Papers by Hikaru Saji
Plant and Cell Physiology, 2001
Plant and Cell Physiology, Mar 1, 1999
Journal of Japan Society of Air Pollution, 2009
Plant Molecular Biology, Nov 1, 2003
To analyze cellular responses to ozone (O3), we performed a large-scale analysis of the Arabidops... more To analyze cellular responses to ozone (O3), we performed a large-scale analysis of the Arabidopsis transcriptome after plants were exposed to O3 for 12 h. By using cDNA macroarray technology, we identified 205 non-redundant expressed sequence tags (ESTs) that were regulated by O3. Of these, 157 were induced and 48 were suppressed by O3. A substantial proportion of these ESTs had predicted functions in cell rescue/defense processes. Using these isolated ESTs, we also undertook a comprehensive investigation of how three hormones, ethylene (ET), jasmonic acid (JA), and salicylic acid (SA), interact to regulate O3-induced genes in various genetic backgrounds of Arabidopsis, such as the ET-insensitive ein2-1, JA-resistant jar1-1, and SA-insensitive npr1-1. The expression of half of the 157 induced genes, especially cell rescue/defense genes, was controlled by ET and JA signaling, indicating that O3-induced defense gene expression at this stage was mainly regulated by ET and JA. Clustering analysis of the 157 O3-induced gene expressions revealed that multiple signal pathways act mutually antagonistically to induce the expression of these genes, and many cell rescue/defense genes induced by ET and JA signal pathways were suppressed by SA signaling, suggesting that the SA pathway acts as a strong antagonist to gene expression induced by ET and JA signaling.
Plant and Cell Physiology, 2002
Plant and Cell Physiology, 2001
Plant Physiology, 2001
Cysteine (Cys) synthase [O-acetyl-l-Ser(thiol)-lyase, EC 4.2.99.8; CSase] is responsible for the ... more Cysteine (Cys) synthase [O-acetyl-l-Ser(thiol)-lyase, EC 4.2.99.8; CSase] is responsible for the final step in biosynthesis of Cys. Transgenic tobacco (Nicotiana tabacum; F1) plants with enhanced CSase activities in the cytosol and in the chloroplasts were generated by cross-fertilization of two transformants expressing cytosolic CSase or chloroplastic CSase. The F1transgenic plants were highly tolerant to toxic sulfur dioxide and sulfite. Upon fumigation with 0.1 μL L−1 sulfur dioxide, the Cys and glutathione contents in leaves of F1 plants were increased significantly, but not in leaves of non-transformed control plants. Furthermore, the leaves of F1 plants exhibited the increased resistance to paraquat, a herbicide generating active oxygen species.
Plant and Cell Physiology, 2001
Plant and Cell Physiology, 2001
Scientific Reports
Ozone is a phytotoxic air pollutant that has various damaging effects on plants, including chloro... more Ozone is a phytotoxic air pollutant that has various damaging effects on plants, including chlorosis and growth inhibition. Although various physiological and genetic studies have elucidated some of the mechanisms underlying plant ozone sensitivity and lesion development, our understanding of plant response to this gas remains incomplete. Here, we show evidence for the involvement of certain apoplastic proteins called phytocyanins, such as AtUC5, that protect against ozone damage. Two representative ozone-inducible responses, chlorosis and stomatal closure, were suppressed in AtUC5-overexpressing plants. Analysis of transgenic plants expressing a chimeric protein composed of AtUC5 fused to green fluorescent protein indicated that this fusion protein localises to the apoplast of plant cells where it appears to suppress early responses to ozone damage such as generation or signalling of reactive oxygen species. Moreover, yeast two-hybrid analyses suggest that AtUC5 may physically inte...
The Janapese Society for Chemical Regulation of Plants, Abstract, 2005
isochorismate pathway is negatively regulated by salicylic acid signaling in O 3-exposed Arabidopsis
Ozone (O 3), a major photochemical oxidant, induces leaf injury concomitant with salicylic acid (... more Ozone (O 3), a major photochemical oxidant, induces leaf injury concomitant with salicylic acid (SA) synthesis. In pathogen-infected leaves, SA is synthesized via two pathways, involving phenylalanine or isochorismate. SA biosynthesis under O 3 fumigation is not well understood. When we applied 14 C-labeled benzoic acid (a precursor of SA in the pathway via phenylalanine) to O 3-exposed tobacco leaves, it was effectively metabolized to SA. However, the activity and mRNA level of isochorismate synthase (ICS) were not increased. In contrast, ICS activity was increased in O 3-exposed Arabidopsis thaliana L. These results suggest that SA is synthesized via benzoic acid from phenylalanine in O 3-exposed tobacco leaves but via isochorismate in Arabidopsis. Ethylene is a plant hormone that promotes leaf damage in O 3-exposed plants. During O 3 exposure, transgenic plants with a phenotype of reduced O 3-induced ethylene production accumulated less SA than did wild-type plants. O 3 increased the activity of phenylalanine ammonia-lyase (PAL) and the transcript levels of the chorismate mutase (CM) and PAL genes in wild-type tobacco, but their induction was suppressed in the transgenic plants. These results indicate that ethylene promotes SA accumulation by regulating the expression of the CM and PAL genes in O 3-exposed tobacco.
Plant and Cell Physiology, 2001
Plant and Cell Physiology, Mar 1, 1999
Journal of Japan Society of Air Pollution, 2009
Plant Molecular Biology, Nov 1, 2003
To analyze cellular responses to ozone (O3), we performed a large-scale analysis of the Arabidops... more To analyze cellular responses to ozone (O3), we performed a large-scale analysis of the Arabidopsis transcriptome after plants were exposed to O3 for 12 h. By using cDNA macroarray technology, we identified 205 non-redundant expressed sequence tags (ESTs) that were regulated by O3. Of these, 157 were induced and 48 were suppressed by O3. A substantial proportion of these ESTs had predicted functions in cell rescue/defense processes. Using these isolated ESTs, we also undertook a comprehensive investigation of how three hormones, ethylene (ET), jasmonic acid (JA), and salicylic acid (SA), interact to regulate O3-induced genes in various genetic backgrounds of Arabidopsis, such as the ET-insensitive ein2-1, JA-resistant jar1-1, and SA-insensitive npr1-1. The expression of half of the 157 induced genes, especially cell rescue/defense genes, was controlled by ET and JA signaling, indicating that O3-induced defense gene expression at this stage was mainly regulated by ET and JA. Clustering analysis of the 157 O3-induced gene expressions revealed that multiple signal pathways act mutually antagonistically to induce the expression of these genes, and many cell rescue/defense genes induced by ET and JA signal pathways were suppressed by SA signaling, suggesting that the SA pathway acts as a strong antagonist to gene expression induced by ET and JA signaling.
Plant and Cell Physiology, 2002
Plant and Cell Physiology, 2001
Plant Physiology, 2001
Cysteine (Cys) synthase [O-acetyl-l-Ser(thiol)-lyase, EC 4.2.99.8; CSase] is responsible for the ... more Cysteine (Cys) synthase [O-acetyl-l-Ser(thiol)-lyase, EC 4.2.99.8; CSase] is responsible for the final step in biosynthesis of Cys. Transgenic tobacco (Nicotiana tabacum; F1) plants with enhanced CSase activities in the cytosol and in the chloroplasts were generated by cross-fertilization of two transformants expressing cytosolic CSase or chloroplastic CSase. The F1transgenic plants were highly tolerant to toxic sulfur dioxide and sulfite. Upon fumigation with 0.1 μL L−1 sulfur dioxide, the Cys and glutathione contents in leaves of F1 plants were increased significantly, but not in leaves of non-transformed control plants. Furthermore, the leaves of F1 plants exhibited the increased resistance to paraquat, a herbicide generating active oxygen species.
Plant and Cell Physiology, 2001
Plant and Cell Physiology, 2001
Scientific Reports
Ozone is a phytotoxic air pollutant that has various damaging effects on plants, including chloro... more Ozone is a phytotoxic air pollutant that has various damaging effects on plants, including chlorosis and growth inhibition. Although various physiological and genetic studies have elucidated some of the mechanisms underlying plant ozone sensitivity and lesion development, our understanding of plant response to this gas remains incomplete. Here, we show evidence for the involvement of certain apoplastic proteins called phytocyanins, such as AtUC5, that protect against ozone damage. Two representative ozone-inducible responses, chlorosis and stomatal closure, were suppressed in AtUC5-overexpressing plants. Analysis of transgenic plants expressing a chimeric protein composed of AtUC5 fused to green fluorescent protein indicated that this fusion protein localises to the apoplast of plant cells where it appears to suppress early responses to ozone damage such as generation or signalling of reactive oxygen species. Moreover, yeast two-hybrid analyses suggest that AtUC5 may physically inte...
The Janapese Society for Chemical Regulation of Plants, Abstract, 2005
isochorismate pathway is negatively regulated by salicylic acid signaling in O 3-exposed Arabidopsis
Ozone (O 3), a major photochemical oxidant, induces leaf injury concomitant with salicylic acid (... more Ozone (O 3), a major photochemical oxidant, induces leaf injury concomitant with salicylic acid (SA) synthesis. In pathogen-infected leaves, SA is synthesized via two pathways, involving phenylalanine or isochorismate. SA biosynthesis under O 3 fumigation is not well understood. When we applied 14 C-labeled benzoic acid (a precursor of SA in the pathway via phenylalanine) to O 3-exposed tobacco leaves, it was effectively metabolized to SA. However, the activity and mRNA level of isochorismate synthase (ICS) were not increased. In contrast, ICS activity was increased in O 3-exposed Arabidopsis thaliana L. These results suggest that SA is synthesized via benzoic acid from phenylalanine in O 3-exposed tobacco leaves but via isochorismate in Arabidopsis. Ethylene is a plant hormone that promotes leaf damage in O 3-exposed plants. During O 3 exposure, transgenic plants with a phenotype of reduced O 3-induced ethylene production accumulated less SA than did wild-type plants. O 3 increased the activity of phenylalanine ammonia-lyase (PAL) and the transcript levels of the chorismate mutase (CM) and PAL genes in wild-type tobacco, but their induction was suppressed in the transgenic plants. These results indicate that ethylene promotes SA accumulation by regulating the expression of the CM and PAL genes in O 3-exposed tobacco.