Hirofumi Saneoka
Hiroshima University
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Featured researches published by Hirofumi Saneoka.
Biologia Plantarum | 2006
Yoshiyuki Ohashi; Nobuhiro Nakayama; Hirofumi Saneoka; Kounosuke Fujita
Changes in plant growth, photosynthetic gas exchange, chlorophyll fluorescence and stem diameter of soybean [Glycine max (L.) Merr.] plants under drought stress were studied. Total plant dry mass was reduced by 30 % compared to well-watered control plants. Leaf water potential was slightly decreased by water stress. Water stress induced daytime shrinkage and reduced night-time expansion of stem. Photosynthetic rate, stomatal conductance and transpiration rate were significantly declined by water stress, while the intercellular CO2 concentration was changed only slightly at the initiation of stress treatment. The maximum photochemical efficiency of photosystem 2 and apparent photosynthetic electron transport rate were not changed by water stress.
Plant Science | 2011
Synsuke Kanai; Reda E. A. Moghaieb; Hany A. El-Shemy; Rashmi Panigrahi; Pravat K. Mohapatra; Junki Ito; Nguyen Tran Nguyen; Hirofumi Saneoka; Kounosuke Fujita
The potassium requirement of green house tomatoes is very high for vegetative growth and fruit production. Potassium deficiency in plants takes long time for expression of visible symptoms. The objective of this study is to detect the deficiency early during the vegetative growth and define the roles of aquaporin and K-channel transporters in the process of regulation of water status and source-sink relationship. The tomato plants were grown hydroponically inside green house of Hiroshima University, Japan and subjected to different levels of K in the rooting medium. Potassium deficiency stress decreased photosynthesis, expansion and transport of ¹⁴C assimilates of the source leaf, but the effects became evident only after diameter expansion of the growing stem (sink) was down-regulated. The depression of stem diameter expansion is assumed to be associated with the suppression of water supply more than photosynthate supply to the organ. The stem diameter expansion is parameterized by root water uptake and leaf transpiration rates. The application of aquaporin inhibitor (AgNO₃) decreased leaf water potential, stem expansion and root hydraulic conductance within minutes of application. Similar results were obtained for application of the K-channel inhibitors. These observations suggested a close relationship between stem diameter expansion and activities of aquaporins and K-channel transporters in roots. The deficiency of potassium might have reduced aquaporin activity, consequently suppressing root hydraulic conductance and water supply to the growing stem for diameter expansion and leaf for transpiration. We conclude that close coupling between aquaporins and K-channel transporters in water uptake of roots is responsible for regulation of stem diameter dynamics of green house tomato plants.
Soil Science and Plant Nutrition | 1999
Halil Kurban; Hirofumi Saneoka; Kunito Nehira; Rahmutulla Adilla; Kounosuke Fujita
Abstract Leguminous plant Alhagi pseudoalhagi was subjected to 0 (control), 50, 100, and 200 mM NaCI treatments during a 30 d period to examine the mechanism of tolerance to salinity. Plant dry weight, net CO2 assimilation rate, leaf stomatal conductance, intercellular CO2 concentration, and solute concentration in leaves, stems, and roots were determined. Total plant weight in the 50 mM treatment was 170% of that of the control after 10 d of treatment. Total plant weight was lower in the 100 and 200 mM treatments than in the control. The leaf CO2 assimilation rate was approximately 150% of that of the control in the 50 mM treatment, but was not affected significantly by 100 mM of NaCI, while it was reduced to about 60% of that the control in the 200 mM treatment. Similarly stomatal conductance was consistent with the CO2 assimilation rate regardless of the treatments. Intercellular CO2 concentration was lower in the NaCI-treated plants than in the control. Changes in CO2 assimilation rate due to salinity...
Journal of Plant Physiology | 2001
Hirofumi Saneoka; Satoshi Ishiguro; Reda E.A. Moghaieb
Summary The effects of salt stress and abscisic acid (ABA) on the expression of betaine aldehyde dehydrogenase (BADH) were determined in sorghum ( Sorghum bicolor L.) plants. BADH mRNA expression was induced by salinity, and the timing coincided with the observed glycinebetaine (betaine) accumulation. The leaf water potential in the leaves of the sorghum plants was significantly affected by salinity. In response to salinity, betaine, ABA, Na and Cl accumulations increased 6-, 16-, 90-, and 3-fold, respectively. In the leaf disks from unsalinized plants incubated on NaCl, or ABA solution, the BADH mRNA level was lower than in the ABA-treated disks. Exogenous application of the ABA biosynthetic inhibitor fluridone to the NaCl-treated disks reduced the ABA accumulation and BADH mRNA levels compared with NaCl-treated leaves. The results indicate that the salt-induced accumulation of betaine and BADH mRNA coincides with the presence of ABA.
Soil Science and Plant Nutrition | 1999
Hirofumi Saneoka; Katsunori Shiota; Halil Kurban; Muhammad Iqbal Chaudhary; Kounosuke Fujita
Abstract Wheat (Triticum aestivum L.) line, Saline Agriculture Research Center line 1 (SARC), was selected in a salinity tolerance improvement program at the University of Agriculture, Faisalabad, Pakistan. In this study we compared SARC with Pothowar which is a common wheat cultivar grown in the same region, in order to study the mechanism of salinity tolerance in the SARC line. Two wheat lines were planted in pots and were subjected to salt stress by daily application of a 200 mM NaCI solution for 30 d during the vegetative growth stage. Dry weight of plant parts, leaf area, leaf water status, and solute concentrations in the cell sap of the leaf tissues were determined at 13 and 30 d after initiation of the stress treatment. Decrease in the plant dry weight and leaf area due to salt stress was more pronounced in Pothowar than in SARC, indicating that SARC was more tolerant to salinity. SARC maintained a higher turgor at low leaf water potentials and showed a higher capacity of osmotic adjustment compar...
Frontiers in Physiology | 2017
Dekoum V.M. Assaha; Akihiro Ueda; Hirofumi Saneoka; Rashid Al-Yahyai; Mahmoud W. Yaish
Ionic stress is one of the most important components of salinity and is brought about by excess Na+ accumulation, especially in the aerial parts of plants. Since Na+ interferes with K+ homeostasis, and especially given its involvement in numerous metabolic processes, maintaining a balanced cytosolic Na+/K+ ratio has become a key salinity tolerance mechanism. Achieving this homeostatic balance requires the activity of Na+ and K+ transporters and/or channels. The mechanism of Na+ and K+ uptake and translocation in glycophytes and halophytes is essentially the same, but glycophytes are more susceptible to ionic stress than halophytes. The transport mechanisms involve Na+ and/or K+ transporters and channels as well as non-selective cation channels. Thus, the question arises of whether the difference in salt tolerance between glycophytes and halophytes could be the result of differences in the proteins or in the expression of genes coding the transporters. The aim of this review is to seek answers to this question by examining the role of major Na+ and K+ transporters and channels in Na+ and K+ uptake, translocation and intracellular homeostasis in glycophytes. It turns out that these transporters and channels are equally important for the adaptation of glycophytes as they are for halophytes, but differential gene expression, structural differences in the proteins (single nucleotide substitutions, impacting affinity) and post-translational modifications (phosphorylation) account for the differences in their activity and hence the differences in tolerance between the two groups. Furthermore, lack of the ability to maintain stable plasma membrane (PM) potentials following Na+-induced depolarization is also crucial for salt stress tolerance. This stable membrane potential is sustained by the activity of Na+/H+ antiporters such as SOS1 at the PM. Moreover, novel regulators of Na+ and K+ transport pathways including the Nax1 and Nax2 loci regulation of SOS1 expression and activity in the stele, and haem oxygenase involvement in stabilizing membrane potential by activating H+-ATPase activity, favorable for K+ uptake through HAK/AKT1, have been shown and are discussed.
Plant Cell Tissue and Organ Culture | 2001
Nobukazu Tanaka; Yukichi Fujikawa; Mohammed A. M. Aly; Hirofumi Saneoka; Kounosuke Fujita; Ichiro Yamashita
Hairy roots were efficiently induced from seedlings of Egyptian clover (berseem clover, Trifolium alexandrinum L.) by infection with Agrobacterium rhizogenes strain DC-AR2 (harboring mikimopine-type pRi1724) and cultured on Murashige-Skoogs (MS) medium containing 1 mg l−1 naphthaleneacetic acid (NAA). Each of the hairy root lines showed variations in growth on solid MS medium containing various concentrations of NAA and these variations were also found in culture in liquid MS medium containing 0.5 mg l−1 NAA. To investigate whether the growth capacity is related to the endogenous auxin IAA and the expression of oncogenes on Ri plasmid T-DNA, the concentration of IAA was determined by ELISA using IAA-specific antibody and the extent of transcripts of oncogenes rolB and rolC was analyzed by Northern blot hybridization. From these results, in hairy roots of Egyptian clover, a rolB expression seemed to influence the intrinsic growth capacity and to call for the proper level in order that the hairy roots grew vigorously, while the endogenous IAA seemed to directly affect the growth capacity on medium without exogenous auxin.
Soil Science and Plant Nutrition | 2000
Reda E.A. Moghaieb; Nobukazu Tanaka; Hirofumi Saneoka; Hashem Ahmed Hussein; Sawsan Samy Yousef; Mohamed Abu-Fandoud Ewada; Mohamed A. Aly; Kounosuke Fujita
Abstract Genetically engineered tomato hairy root lines with the ability to synthesize glycine betaine were established by introducing the betaine aldehyde dehydrogenase gene (BADH-1) from sorghum plants. The lines showed a mikimopine activity, confirming the transformation with pRi plasmid. The stable integration of the BADH gene into the tomato genome was confirmed by Southern blotting analysis. The expression of BADH mRNA could be detected in the tomato hairy roots by Northern analysis. The osmotic potential (Ψ s) of the transgenic hairy roots was sufficient to allow water uptake. The accumulation of betaine was detected by 1H-NMR analysis. The accumulation of betaine in the transgenic hairy roots contributed to the maintenance of the osmotic potential of the cells.
Soil Science and Plant Nutrition | 2012
Yoshiyuki Ohashi; Hirofumi Saneoka; Kounosuke Fujita
Abstract Siratro (Macroptilium atropurpureum) and soybean (Glycine max) were grown in pots with or without irrigation for 3 weeks at the vegetative stage to examine the effect of water stress on plant biomass production, biological N2 fixation, CO2 assimilation rate, stomatal conductance, leaf water potential, and the partition of 14CO2 to plant parts. Biomass production decreased by water stress and the decrease was less conspicuous in siratro, mainly due to the maintenance of a relatively higher growth rate in stem plus petioles and roots. Siratro maintained a higher stomatal conductance and CO2 assimilation rate at a lower leaf water potential compared to soybean. Water stress decreased the biological N2 fixation in both species, and the decrease was more appreciable in siratro than in soybean under stress conditions. Water stress affected the export of photoassimilates from leaves in both species. The translocation of 14CO2 photoassimilates to nodules and roots was less substantial in siratro than in soybean under water stress conditions. Translocation of photoassimilates from leaves to stem plus petioles in siratro enables the maintenance of growth of stem and petioles under water stress conditions.
GM crops & food | 2011
Reda E.A. Moghaieb; Akiko Nakamura; Hirofumi Saneoka; Kounosuke Fujita
Ectoine is a common compatible solute in halophilic bacteria. Its biosynthesis originates from L-aspartate β-semialdehyde and requires three enzymes: L-2, 4-diaminobutyric acid aminotransferase (gene: ect B), L-2,4-diaminobutyric acid acetyl transferase (gene: ect A) and L-ectoine synthase (gene: ect C). Genetically engineered tomato plants expressing the three H. elongata genes (ectA, ectB, and ectC) generated showed no phenotypic abnormality. Expression of the ectoine biosynthetic genes was detected in the T3 transgenic plants by Northern blot analysis. The ectoine accumulating T3 plants were evaluated for salt tolerance by examining their photosynthestic activity, osmotic adjustment and carbon partitioning. Nuclear magnetic resonance (NMR) detected the accumulation of ectoine. The concentration of ectoine increased with increasing salinity. The transgenic lines showed higher activities of peroxidase, while the malondialdehyde (MDA) concentration was decreased under salinity stress condition. In addition, preservation of higher rates of photosynthesis and turgor values as compared to control was evident. Within a week of 13CO2 feeding, salt application led to increases in the partitioning of 13C into roots at the expense of 13C in the other plant parts. These results suggest that under saline conditions ectoine synthesis is promoted in the roots of transgenic plants, leading to an acceleration of sink activity for photosynthate in the roots. Subsequently, root function such as water uptake is improved, compared with wild-type plants. In this way, the photosynthetic rate is increased through enhancement of cell membrane stability in oxidative conditions under salt stress.