Tohru Okuda

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 ...

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.

Changes in the ultrastructures of crown cells of winter wheat during wintering under snow

Abstract Electron microscopic studies were carried out to examine cytological events in crown cells of wheat during wintering under snow. Two cultiyars of winter wheat were used for the ultrastructural studies: Triticum aestivum L. cv. Horoshirikomugi and Norin 61. In October and November, the cells of these cultivars had similar ultrastructure which was characteristic of cells engaged in protein synthesis and proliferation of organelles. After this period, the two cultivars exhibited different changes in ultrastructure. The changes in the Horoshirikomugi cultivar could be divided into four phases: 1) an active, growing phase in the fall; 2) a second phase, initiated when the field was covered with snow; 3) a third phase that commenced in late February; and 4) a fourth phase that could be detected in June under conditions that simulated wintering. The second and third phases in the process were apparently absent in Norin 61 and the cellular events in this cultivar seemed to proceed directly from the initi...

Characterization of oligo(dT)-binding proteins from seedlings of winter wheat

Abstract Oligo(dT)-binding proteins of winter wheat (Triticum aestivum L.) seedlings were separated into two fractions by chromatography on oligo(dT)-cellulose; one fraction was eluted sequentially with 10 mM Tris-HCl (D fraction) and the other was eluted with the same buffer supplemented with 500 g L-1 formamide (formamide fraction). The proteins associated with the oligo(dT)-cellulose were characterized by SDS-polyacrylamide gel electrophoresis (PAGE) and, out of the more than 17 polypeptides present in the fractions, a set of proteins common to both the D and formamide fractions had an apparent molecular mass of 55 kDa. Two other sets of the isoform proteins with a molecular mass of 35 and 29 kDa, respectively, were present in the formamide fraction. After growth under snow for three months, an apparent increase in the level of polypeptide with a molecular mass of about 80-kDa was detected. Studies with a cell-free translation system showed that the addition of each fraction resulted in a 1.7- to 3.8-f...

Poly(A)+-binding proteins from seedlings of winter wheat

Abstract In the preceding paper, we described the fractionation of oligo(dT)-binding proteins (Oligo(dT)BP) from seedlings of winter wheat by chromatography on oligo(dT)-cellulose according to the procedure of Jeffery (1977); one fraction (designated as fraction D) was eluted in buffer D (10 mM Tris-HCl, pH 7.4), and the other (the formamide fraction) was eluted in the same buffer supplemented with 500 g L-1 formamide. Oligo(dT)BPs from the wheat seedlings in each fraction showed differences in the polypeptide composition.