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Articles by T. Yamamoto
Total Records ( 5 ) for T. Yamamoto
  A. Al-Busaidi , T. Yamamoto , M. Inoue , Y. Mori , M. Irshad and A. Zahoor
  Population growth and global warming would substantially impact the availability and quality of existing freshwater supplies. The utilization of marginal water resources for agriculture is getting considerable importance. The lands irrigated with saline water are required to reduce salts accumulations through leaching and/or drainage practices. A greenhouse experiment was carried out to investigate the effects of saline irrigation and leaching fractions on barley (Hordeum vulgare L.) and salts accumulations in sand dune soil. For this purpose seawater was diluted to the salinity levels of 3 and 13 dS m-1 and applied by drip irrigation at 0.1 and 0.4 leaching fractions (LF). The results of the experiment showed that the saline water significantly impaired barley growth. Higher LF lowered the soil salinity and increased soil water contents. Both quantity and quality of water regulated salts distribution within the soil. The salts were found higher near or immediate below the soil surface. An enhanced LF carried more salts down the soil horizon. Low salts were accumulated in the vicinity of emitters as compared to distant wet area. Higher saline irrigation inhibited evaporation. Infiltration rate and hydraulic conductivity of soil were statistically unchanged across the treatments. Conjunctive use of marginal water at proportional LF could be effective to enhance the yield potential of crops in water scarce areas.
  T Mine , S Katayama , H Kajiwara , M Tsunashima , H Tsukamoto , Y Takakura and T. Yamamoto

We cloned, expressed, and characterized a novel β-galactoside 2,6-sialyltransferase from Photobacterium leiognathi strain JT-SHIZ-119. The protein showed 56–96% identity to the marine bacterial 2,6-sialyltransferases classified into glycosyltransferase family 80. The sialyltransferase activity of the N-terminal truncated form of the recombinant enzyme was 1477 U/L of Escherichia coli culture. The truncated recombinant enzyme was purified as a single band by sodium dodecyl sulfate polyacrylamide gel electrophoresis through 3 column chromatography steps. The enzyme had distinct activity compared with known marine bacterial 2,6-sialyltransferases. Although 2,6-sialyltransferases cloned from marine bacteria, such as Photobacterium damselae strain JT0160, P. leiognathi strain JT-SHIZ-145, and Photobacterium sp. strain JT-ISH-224, show only 2,6-sialyltransferase activity, the recombinant enzyme cloned from P. leiognathi strain JT-SHIZ-119 showed both 2,6-sialyltransferase and 2,6-linkage-specific neuraminidase activity. Our results provide important information toward a comprehensive understanding of the bacterial sialyltransferases belonging to the group 80 glycosyltransferase family in the CAZy database.

  Y Kushi , H Kamimiya , H Hiratsuka , H Nozaki , H Fukui , M Yanagida , M Hashimoto , K Nakamura , S Watarai , T Kasama , H Kajiwara and T. Yamamoto

Bacterial sialyltransferases (STs) from marine sources were characterized using glycosphingolipids (GSLs). Bacterial STs were found to be β-galacotoside STs. There were two types of STs: (1) ST obtained from strains such as ishi-224, 05JTC1 (#1), ishi-467, 05JTD2 (#2), and faj-16, 05JTE1 (#3), which form 2-3 sialic acid (Sia) linkages, named 2-3ST, (2) ST obtained from strains such as ISH-224, N1C0 (#4), pda-rec, 05JTB2 (#5), and pda-0160, 05JTA2 (#6), which form 2-6 Sia linkages, named 2-6ST. All STs showed affinity to neolacto- and lacto-series GSLs, particularly in neolactotetraosyl ceramide (nLc4Cer). No large differences were observed in the pH and temperature profiles of enzyme activities. Kinetic parameters obtained by Lineweaver–Burk plot analysis showed that #3 and #4 STs had practical synthetic activity and thus it became easily possible to achieve large-scale ganglioside synthesis (100–300 µM) using these recombinant enzymes. Gangliosides synthesized from nLc4Cer by 2-3 and 2-6STs were structurally characterized by several analytical and immunological methods, and they were identified as IV3NeuAc-nLc4Cer(S2-3PG) and IV6NeuAc-nLc4Cer (S2-6PG), respectively. Further characterization of these STs using lactotetraosylceramide (Lc4Cer), neolactohexaosylceramide (i antigen), and IV6kladoLc8Cer (I antigen) showed the synthesis of corresponding gangliosides as well. Synthesized gangliosides showed binding activity to the influenza A virus [A/panama/2007/99 (H3N2)] at a similar level to purified S2-3PG and S2-6PG from mammalian sources. The above evidence suggests that these STs have unique features, including substrate specificities restricted to lacto- and neolactoseries GSLs, as well as catalytic potentials for ganglioside synthesis. This demonstrates that efficient in vitro ganglioside synthesis could be a valuable tool for selectively synthesizing Sias modifications, thereby permitting the exploration of unknown functions.

  B.A. Ould Ahmed , T. Yamamoto and M. Inoue
  Saline-water drip irrigated sorghum varietal response to limited available soil water in dune sand was assessed using salinity response function. In a randomized complete block design three sorghum varieties (Local sorghum, BK 16 and EC 90) were grown with drip irrigated saline-water, at four salinity levels (5.47, 7.32, 9.38 and 12.50 dS m-1) and with quality water of 0.11 dS m-1 serving as the control. Four salinity response models were used to assess their ability to discriminate salinity-induced grain yield differences under limited available soil water. Response analysis indicated the four models were equally good in fitting that the grain yield data, but the modified discount model produced the consistently the best fit. Analysis of the data indicated that the impact of salinity stress on varieties was best discriminated by the parameters salinity threshold (Ct), Salinity Tolerance index (ST-index) and the salinity at which 50 % grain reduction (C50) occurred. The analysis indicated that the variety BK 16 was the most tolerance to salinity stress.
  H. Dehghanisanij , T. Yamamoto , M. Inoue and M. Akbari
  The scarcity of fresh water in arid and semi-arid regions (ASAR) makes saline water a valuable alternative water source for irrigation of agriculture crops, if we can improve the management of saline water to avoid its deleterious effects. Variables affecting soil water content (θw) and soil solute salinity (ECw), including time after irrigation and crop growth stages; early (ES), mid (MS) and late (LS) stages, were investigated at different radius from the emitter (lateral pipe). The simultaneous distribution of water and solute under drip irrigation was measured using Time Domain Reflectometry (TDR) method. The results indicated that θw and ECw increased in the order ES < MS < LS. The maximum θw and minimum ECw coincided at 10 cm radius from emitter (r10) during ES, MS and LS. The same trend applied for 20 cm radius from emitter (r20) during ES and MS. The ECw increased significantly in the order r10 < r20 < r30 during all crop growth stages. Time elapsed since irrigation was terminated till θw increased to a maximum level at the r10, during ES, MS and LS was 4, 3 and 3 h, respectively. It is therefore suggested that irrigation should commence 3 h before noon to coincide the maximum θw (minimum ECw) with maximum crop evapotranspiration (ETc). Interaction between θw and ECw for a given radius and different crop growing stages showed that the influence of θw on ECw was restricted to a small radius of about 20 cm from the emitter, which decreased further to only 10 cm during LS. Beyond this range, increasing θw was not enough to significantly affect ECw. The information obtained from this research is essential for the design, operation and management of saline water use with drip irrigation system in sand dune fields.
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