Shonosuke Sagisaka

An immediate and steep increase in atp concentration in response to reduced turgor pressure in escherichia coli b

Osmotic treatment with sodium chloride of Escherichia coli B growing in the logarithmic phase induced an immediate increase in ATP concentration in response to increased concentrations of added solute in its growth medium in the first 10 min of the addition. After that, ATP concentration decreased gradually. Sodium arsenate and potassium fluoride almost abolished the ATP increase. The time course of the increase was quite different from that of cells treated with inhibitors of protein synthesis. The osmotic treatment did not decrease the viability of cells. In addition, there was no degradation of RNA by 5 min after sodium chloride addition, and, further, the lag time of ATP increase was extended by an inhibitor of nucleotide synthesis. These results indicated that a major fraction of the stress-increased ATP resulted from de novo synthesis, and that it was mainly dependent upon the reaction of substrate-level phosphorylation, which is regulated by turgor pressure.

Relationship between wintering ability of winter wheat and the extent of depression of carbohydrate reserves: Basal metabolic rate under snow determines longevity of plants

Abstract Differences in metabolic activities of winter wheat (Triticum aestivum L.) under snow were assessed in two cultivars, Horoshirikomugi and Norin 61, which exhibit different longevity during wintering. From October, through winter to spring, changes in the levels of carbohydrates, sugar phosphates, glutathione, amino acids, inorganic ions, and osmotic pressure were monitored. When the ground was covered with snow, autotrophic metabolism in wheat ceased. The expenditure of stored carbohydrates, mainly fructans and sucrose, in the tissues appeared to be controlled to such an extent in the two respective cultivars that it proceeded at rates commensurate with the demands of the cells; the difference in the extent of consumption (1.3 to 1.7 μmol in the stem of Horoshirikomugi during the period from February 16 to March 16 and 10 μmol in that of Norin 61 from December 26 to January 18, g-1 fresh weight day-1was directly related to the longevity of the plants under snow. The difference may arise from the ...

Major Isoforms of Starch Branching Enzymes in Premature Seeds of Kidney Bean (Phaseolus vulgaris L.)

Developing seeds of the kidney bean (Phaseolus vulgaris L.) contain several isoforms of starch branching enzymes. Two of them, KBE1 and KBE2, which are the major forms in the premature seeds, were purified as a single band of protein on SDS-PAGE and native PAGE by chromatographies on DEAE-Sepharose, Bio-Gel P-200, and amylose-binding Sepharose 6B. The enzymes had similar pH optimum (7.0), pH stability (7.0-9.5), temperature optimum (25-30°C), and temperature stability (up to 40°C). Additionally, both were inhibited by various divalent metal ions and activated by citrate. Finally, though their N-terminal amino acid sequences were identical, their molecular masses and affinities for amylose differed; 80 kDa and 1.27 mM for KBE1 and 77 kDa and 0.74 mM for KBE2.

Ultrastructure of poplar cortical cells during the transition from growing to wintering stages and vice versa

SummaryElectron microscopic studies revealed that major cytological changes in the cortical cells of poplar (Populus euramericana cv. gelrica) began to occur in early September in conjunction with the metabolic transition from the growing to the wintering stage. During this transition, the cells became temporarily rich in endoplasmic reticulum, polysomes and vesicles. As the conspicuous formation of organelles progressed, the large vacuoles became smaller and filled with osmiophilic materials. Undefined organelles (protein-lipid bodies) also increased in number. From late October until March, organelles involved in protein synthesis were sparsely distributed in the cells, indicating that the number of these organelles is probably linked to the seasonal cycle of protein synthesis. In early February, after release from dormancy, fusion of vacuoles proceeded in the cells. The inclusion of organelles and a gradual decrease in the amount of osmiophilic materials in the vacuoles occurred at this stage. Subsequently, the structure of the cells continued to undergo changes to accommodate growth, which occurred in early May.

Occurrence of unidentified bodies that resemble “plastid initials” in poplar cells after breaking of dormancy in midwinter

SummaryElectron-microscopic studies of plastids in cortical cells of poplar (Populus euramericana cv. gelrica) were carried out to examine whether any structural changes were initiated after breaking of dormancy in midwinter under non-growing conditions. After the breaking of dormancy, ultrastructural changes became evident and the profiles of plastids became heterogeneous. Organelles resembling the “plastid initials” proposed by Mühlenthaler and Frey-Wyssling in 1965 were frequently observed concomitant with changes in the plastid envelope. The formation of “plastid initials” appeared to be initiated by the formation of septa in pre-existing plastids. After this stage, narrow connections appeared between the “initials” and the parent plastids. Approximately 50 days after the breaking of dormancy in late March, further heterogeneity in the profiles of plastids was observed. At this stage, young plastids (plastids without starch granules) were frequently observed and the formation of “plastid initials” was hardly ever observed. These observations suggest that the “plastid initials” may be present for only a limited period in the cortical cells of the poplar and may be the precursors of the proplastids. Similar ultrastructural profiles were found in cortical cells of mulberry and in leaf buds of apple trees, suggesting that such changes in the ultrastructure of plastids are a general feature of perennials.

Malfunction of Enzyme Systems Involved in the Regeneration of Glutathione in Perennials at Low Temperatures.

When frozen flower buds of apple trees started to thaw, an abrupt decrease of levels of reduced glutathione and glucose-6-phosphate occurred, even without freezing injuries. With freezing injuries, a steep decrease in the levels of the above substrates was observed, suggesting that the level of generating peroxide depends on freezing temperatures. Enzyme systems involved in the regeneration of reduced glutathione also do not seem to function properly in poplar twigs in a frozen milieu. At about - 10°C, a decrease in levels of reduced glutathione was detected and this decrease was followed by a decrease in levels of glucose 6-phosphate. When twigs that contained depressed levels of reduced glutathione and glucose-6-phosphate were transferred to 4°C, overcompensation for the decrease in reduced glutathione and glucose-6-phosphate occurred and the resultant surplus appeared to reflect the metabolic dysfunction in the supply and demand for reduced glutathione and glucose-6-phosphate that occurs under frozen conditions. These results suggest that the sequence of reactions which starts from the reaction catalyzed by hexokinase, through reactions catalyzed by glucose-6-phosphate dehydrogenase and glutathione reductase, does not function properly under frozen conditions in perennial plants.

An Increase in Levels of Glutathione in Escherichia coli B caused by Osmotic Stress

pressure and driven by ATP.4) In our previous paper, we found an increase in the concentration of ATP in E. coli as a specific result of osmotic stress.5) Glutathione is a tripeptide present in all living cells and has been reported to have a palliative effect under various stressful conditions. It appears to be involved in thermotolerance,6) radioprotection,7) the induction of stress protein,8) and so on. Until now, there

Dependence of Wintering Higher Plants on Basal Metabolic Rates and Threshold Concentrations of Hexose for Survival and Regrowth

Abstract The influence of the environment on the life of higher plants, both in the long term and in the short term, is of considerable interest. Studies on death due to high temperature and water loss in relation to geological survival—a long term problem—(Lovelock and Whit-field 1982; Brock 1985; Kasting and Ackerman 1986; Caldeira and Kasting 1992) and injuries resulting from environmental pllution or low temperature—a short term problem—(Sakai 1961, 1965; Koopowitz and Kaye 1983; Pierre and Quiroz 1988) are of major importance to understand the life span of biosphere.

Comparative studies of the changes in enzymatic activities in hardy and less hardy cultivars of winter wheat in late fall and in winter under snow

Abstract The synthetic activity of protein and changes in the activity profiles of enzymes during cold acclimation were studied in leaves, stems, and crowns of a hardy winter wheat cultivar ( Triticum aestivum L. cv. Horoshirikomugi) and a less hardy winter wheat cultivar (Triticum aestivum L. cv. Norin 61). The results showed that one of the genetic differences between the two cuitivars is found in the activities of protein synthesis under low temperatures. The profiles of the changes in enzymatic activities showed that the adjustment of enzymatic activities was a tissue-specific event to accommodate environmental changes. The synthesis of the enzymes involved in a peroxide scavenging system such as hexokinase, glucose-6-phosphate dehydrogenase, dehydroascorbate reductase, ascorbate peroxidase, and so on started at the acclimation stage, while the phosphoglucose isomerase, which appears to be a maintenance-type enzyme in the wintering wheat, showed a small increase in the activity at later stages of accl...

Differences in activities related to cessation of synthesis of inducible proteins as an early response to cold between hardy and less hardy cultivars of winter wheat

Using two sets of cultivars, two hardy and two less hardy ones, we studied differences in the regulation of the synthesis of cold-inducible proteins at an early stage of cold acclimation. During 11 days of cold treatment, all four cultivars had changes in rates of protein synthesis, which were divided into four phases. The difference in the regulation of synthesis of the protein was evident at the third and fourth phases. In the less hardy cultivars, rates of synthesis of cold-inducible proteins started to decline and the profiles of proteins being synthesized resembled those of control samples (without cold treatment). In hardy cultivars, rates of synthesis of typical cold-inducible proteins remained unchanged, suggesting that some regulatory mechanisms regulate the continued cold-inducible synthesis of proteins in the latter cultivars by acting, presumably, at particular target sites within the crown cells. Analysis of freezing tolerance showed that in stems and crowns of winter wheat, the cold-inducible proteins do not contribute directly to the freezing tolerance, while some may have roles in bringing about increased longevity in cold environments.