Browsing by Author "Teruhiro Takabe"

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Abiotic stress tolerance in plants
(Springer Netherlands, 2006) Ashwani K. Rai; Teruhiro Takabe
The main objective of this book is to provide a state-of-the-art guide to recent developments that help in the understanding of plant response to abiotic stresses. The book contains nine sections in a single compact volume. These sections cover Signal transduction, Temperature stress, Oxidative stresses, Phytoremediation, Osmotic stresses, Ion homeostasis, Nutrition, Structural responses, and Genetic diversity and development of biotechnology. Contributions in each chapter are prepared by leading experts in their respective fields and mirror the advancement in the approach. This book also supplies extensive bibliographies at the end of each chapter, as well as tables and figures that illustrate the research findings. Each chapter reflects how physiologists, biochemists and molecular biologists have caught up with the newer techniques to understand the basic problems of abiotic stress in plant species. All these make this book a useful guide for students, researchers and professionals in many forms of botany. © 2006 Springer. All Rights Reserved.
An alkaline phosphatase/phosphodiesterase, PhoD, induced by salt stress and secreted out of the cells of Aphanothece halophytica, a halotolerant cyanobacterium
(2011) Hakuto Kageyama; Keshawanand Tripathi; Ashwani K. Rai; Suriyan Cha-Um; Rungaroon Waditee-Sirisattha; Teruhiro Takabe
Alkaline phosphatases (APases) are important enzymes in organophosphate utilization. Three prokaryotic APase gene families, PhoA, PhoX, and PhoD, are known; however, their functional characterization in cyanobacteria largely remains to be clarified. In this study, we cloned the phoD gene from a halotolerant cyanobacterium, Aphanothece halophytica (phoD Ap). The deduced protein, PhoD Ap, contains Tat consensus motifs and a peptidase cleavage site at the N terminus. The PhoD Ap enzyme was activated by Ca 2+ and exhibited APase and phosphodiesterase (APDase) activities. Subcellular localization experiments revealed the secretion and processing of PhoD Ap in a transformed cyanobacterium. Expression of the phoD Ap gene in A. halophytica cells was upregulated not only by phosphorus (P) starvation but also under salt stress conditions. Our results suggest that A. halophytica cells possess a PhoD that participates in the assimilation of P under salinity stress. © 2011, American Society for Microbiology.
Anabaena sp. PCC7120 transformed with glycine methylation genes from Aphanothece halophytica synthesized glycine betaine showing increased tolerance to salt
(2012) Rungaroon Waditee-Sirisattha; Meenakshi Singh; Hakuto Kageyama; Daungjai Sittipol; Ashwani K. Rai; Teruhiro Takabe
Photosynthetic, nitrogen-fixing Anabaena strains play an important role in the carbon and nitrogen cycles in tropical paddy fields although they are salt sensitive. Improvement in salt tolerance of Anabaena cells by expressing glycine betaine-synthesizing genes is an interesting subject. Due to the absence of choline in cyanobacteria, choline-oxidizing enzyme could not be used for the synthesis of glycine betaine. Here, the genes encoding glycine-sarcosine and dimethylglycine methyltransferases (ApGSMT-DMT) from a halotolerant cyanobacterium Aphanothece halophytica were expressed in Anabaena sp. strainPCC7120. The ApGSMT-DMT-expressing Anabaena cellswere capable of synthesizing glycine betaine without the addition of any substance. The accumulation level of glycine betaine in Anabaena increased with rise of salt concentration. The transformed cells exhibited an improved growth and more tolerance to salinity than the control cells. The present work provides a prospect to engineer a nitrogen-fixing cyanobacterium having enhanced tolerance to stress by manipulating de novo synthesis of glycine betaine. © Springer-Verlag 2012.
Enrichment of sugar content in melon fruits by hydrogen peroxide treatment
(2009) Keiko Ozaki; Akio Uchida; Tomoko Takabe; Fumi Shinagawa; Yoshito Tanaka; Teruhiro Takabe; Takahisa Hayashi; Tasuku Hattori; Ashwani K. Rai; Tetsuko Takabe
Since sweetness is one of the most important qualities of many fruits, and since sugars are translocated from leaves to fruits, the present study investigates photosynthetic activity, activity of sugar metabolizing enzymes, sugar content in leaves and fruits and endogenous levels of hydrogen peroxide in leaves of melon plants treated with various dilutions of hydrogen peroxide, a nonspecific signaling molecule in abiotic stress. For this purpose, 4-month-old melon plants were treated with various concentrations (<50 mM) of hydrogen peroxide by applying 300 mL per day to the soil of potted plants. The treatments resulted in increased fructose, glucose, sucrose and starch in the leaves and fruits. The most effective concentration of hydrogen peroxide was 20 mM. During the day, soluble sugars in leaves were highest at 12:00 h and starch at 15:00 h. Furthermore, the peroxide treatment increased the photosynthetic activity and the activities of chloroplastic and cytosolic fructose-1,6-bisphosphatase, sucrose phosphate synthase and invertases. Thus, our data show that exogenous hydrogen peroxide, applied to the soil, can increase the soluble sugar content of melon fruits. © 2008 Elsevier GmbH. All rights reserved.
Physiological, biochemical and molecular responses of the halophilic cyanobacterium Aphanothece halophytica to Pi-deficiency
(2013) Keshwanand Tripathi; Naveen Kumar Sharma; Hakuto Kageyama; Teruhiro Takabe; Ashwani Kumar Rai
We studied the responses of a halophilic cyanobacterium Aphanothece halophytica at surplus (normal composition of growth medium containing 125 μM PO43-), sufficient (the minimum concentration supporting optimal growth, 22 μM PO43-) and deficient (no external supply of Pi) concentrations of inorganic phosphate (Pi). The cyanobacterium was able to grow well in Pi-deficient conditions until the end of incubation (14 days), though at a marginally reduced rate. The cellular P-quota in Pi-surplus cells at the end of incubation was 2.7 times that of their initial P-quota (0.75 μmol mg protein-1), and remained fairly high (0.442 μmol mg protein-1) even in Pi-deficient medium. However, cultures growing in Pi-sufficient medium (22 μM PO43-), upon transfer to Pi-deficient medium, exhibited a rapid decline in cellular P level. Furthermore, cells growing in Pi-surplus medium showed a rapid efflux of P into the external medium. Aphanothece halophytica exhibited a biphasic phosphate transport system involving both high- (Ks 2.06 μM) and low-affinity (Ks 17.85 μM) transporters. Cyanobacterial cells maintained a basal level (constitutively expressed and not affected by Pi availability) of alkaline phosphatase (APase) activity, which increased 5-7-fold under Pi-deficiency. Supplementation of phosphate to the medium caused gradual decline in the enzyme activity to the basal level. Pi-deficient cells showed an enhanced level of transcripts for PPi-dependent glycolytic enzymes. Though moderate, Pi-deficiency affected the respiration, photosynthetic rate and electron transport chain activity negatively. PS II activity was most sensitive to Pi-deficiency, followed by PSI and whole chain. Pi-replete A. halophytica cells showed a single high-affinity nitrate transport system. However, deficiency of Pi reduced the nitrate and nitrite reductase activities. © 2013 © British Phycological Society.
Preface
(Springer Netherlands, 2006) Ashwani K. Rai; Teruhiro Takabe
[No abstract available]
Synechococcus sp. PCC7942 transformed with Escherichia coli bet genes produces glycine betaine from choline and acquires resistance to salt stress
(American Society of Plant Biologists, 1995) Mika Nomura; Manabu Ishitani; Teruhiro Takabe; Ashwani K. Rai; Tetsuko Takabe
Synechococcus sp. PCC7942, a fresh water cyanobacterium, was transformed by a shuttle plasmid that contains a 9-kb fragment encoding the Escherichia coli bet gene cluster, i.e. betA (choline dehydrogenase), betB (betaine aldehyde dehydrogenase), betI (a putative regulatory protein), and betT (the choline transport system). The expression of these genes was demonstrated in the cyanobacterial cells (bet-containing cells) by northern blot analysis, as well as by the detection of glycine betaine by 1H nuclear magnetic resonance in cells supplemented with choline. Endogenous choline was not detected in either control or bet-containing cells. Both control and bet-containing cyanobacterial cells were found to import choline in an energy-dependent process, although this import was restricted only to bet-containing cells in conditions of salt stress. Glycine betaine was found to accumulate to a concentration of 45 mM in bet-containing cyanobacterial cells, and this resulted in a stabilization of the photosynthetic activities of photosystems I and II, higher phycobilisome contents, and general protective effects against salt stress when compared to control cells. The growth of bet-containing cells was much faster in the presence of 0.375 M NaCl than that of control cells, indicating that the transformant acquired resistance to salt stress.