Mesurement of Cyanide-Resistant Respiration in Leaf Blade of Rice by Use of Oxygen Isotope Discrimination

A reduction in the dark respiration of rice may improve dry-matter production and yield. To explore the possibility of controlling cyanide-resistant alternative respiration, of which energy production efficiency is low, we constructed a measuring system for cyanide-resistant respiration in leaf blades of rice with the use of oxgen isotope discrimination. Dark respiration was lowest at 10mM KCN, the inhibitor of cytochrome pathway, and it was lowest at 30mM salicylhydroxamic acid (SHAM), the inhibitor of the alternative pathway. Oxygen isotope discrimination was highest when leaf blade had HCN applied for 1 hour after being soaked in 10mM KCM for 3 minutes, and it was lowest when lowest when leaf blade was soaked in 30mM SHAM regardless of the soaking method. The discrimination factors of the alternative oxidase and the cytochrome oxidase of leaf blade were estimination factors of the alternative oxidase and the cytochrome oxidase of leaf blade were estimated as 20.3‰ and 13.9‰, respectively, and the ratio of cyanide-resistant respiration to dark respiration of leaf blade was 38%.イネの暗呼吸の抑制は乾物生産や収量の増大に貢献すると考えられている．エネルギー生産効率の低いシアン耐性呼吸の抑制の可能性を検討するため，酸素同位体分別を利用したシアン耐性呼吸の測定装置を製作し，イネ葉身の測定法を検討した．その結果，葉身の暗呼吸速度はシトクロム経路の阻害剤であるKCN溶液の濃度が10mMのときに，また，シアン耐性呼吸経路の阻害剤であるSHAM溶液の濃度が30mMのときに低下が最大であった．分別係数は３分間10mM KCN溶液に浸漬後HCNに１時間さらした場合に最も高い20.3‰が得られた．いっぽう，SHAM処理では30mMの溶液であれば浸漬法にかかわらず，13.9‰であった．これらから，イネ葉身のオルターティブ酸化酵素とシトクロム酸化酵素の分別係数はそれぞれ20.3‰と13.9‰であると推定され，このときのシアン耐性呼吸の割合は38%であった

Type of Critical Heat Flux for Downward Flow in a Vertical Tube

CHF characteristics of downward flow are quite different from that of upward flow due to complicated two-phase flow structure caused by the influence of buoyancy. In this investigation, CHF experiment was carried out on the forced convective boiling system with astainless steel tube of 15 mm in inner diameter and 400 mm in heating length. As the experimental results on the basis of the axial location of CHF occurrence, the inlet fluid temperature and the pressure drop of test section, CHF could be classified into three modes i.e., the dryout of falling liquid film at high quality condition, the CHF due to flooding at low quality condition and the CHF caused by the instability of two-phase flow structure at near subcooled condition.通計番号 No.14-1

Discrimination based on Gly and Arg/Ser at position 673 between dipeptidyl-peptidase (DPP) 7 and DPP11, widely distributed DPPs in pathogenic and environmental gram-negative bacteria

Porphyromonas gingivalis, an asaccharolytic gram-negative rod-shaped bacterium, expresses the novel Asp/Glu-specific dipeptidyl-peptidase (DPP) 11 (Ohara-Nemoto, Y. et al. (2011) J. Biol. Chem. 286, 38115–38127), which has been categorized as a member of the S46/DPP7 family that is preferential for hydrophobic residues at the P1 position. From that finding, 129 gene products constituting five clusters from the phylum Bacteroidetes have been newly annotated to either DPP7 or DPP11, whereas the remaining 135 members, mainly from the largest phylum Proteobacteria, have yet to be assigned. In this study, the substrate specificities of the five clusters and an unassigned group were determined with recombinant DPPs from typical species, i.e., P. gingivalis, Capnocytophaga gingivalis, Flavobacterium psychrophilum, Bacteroides fragilis, Bacteroides vulgatus, and Shewanella putrefaciens. Consequently, clusters 1, 3, and 5 were found to be DPP7 with rather broad substrate specificity, and clusters 2 and 4 were DPP11. An unassigned S. putrefaciens DPP carrying Ser673 exhibited Asp/Glu-specificity more preferable to Glu, in contrast to the Asp preference of DPP11 with Arg673 from Bacteroidetes species. Mutagenesis experiments revealed that Arg673/Ser673 were indispensable for the Asp/Glu-specificity of DPP11, and that the broad specificity of DPP7 was mediated by Gly673. Taken together with the distribution of the two genes, all 264 members of the S46 family could be attributed to either DPP7 or DPP11 by an amino acid at position 673. A more compelling phylogenic tree based on the conserved C-terminal region suggested two gene duplication events in the phylum Bacteroidetes, one causing the development of DPP7 and DPP11 with altered substrate specificities, and the other producing an additional DPP7 in the genus Bacteroides

Mesurement of Cyanide-Resistant Respiration in Leaf Blade of Rice by Use of Oxygen Isotope Discrimination

A reduction in the dark respiration of rice may improve dry-matter production and yield. To explore the possibility of controlling cyanide-resistant alternative respiration, of which energy production efficiency is low, we constructed a measuring system for cyanide-resistant respiration in leaf blades of rice with the use of oxgen isotope discrimination. Dark respiration was lowest at 10mM KCN, the inhibitor of cytochrome pathway, and it was lowest at 30mM salicylhydroxamic acid (SHAM), the inhibitor of the alternative pathway. Oxygen isotope discrimination was highest when leaf blade had HCN applied for 1 hour after being soaked in 10mM KCM for 3 minutes, and it was lowest when lowest when leaf blade was soaked in 30mM SHAM regardless of the soaking method. The discrimination factors of the alternative oxidase and the cytochrome oxidase of leaf blade were estimination factors of the alternative oxidase and the cytochrome oxidase of leaf blade were estimated as 20.3‰ and 13.9‰, respectively, and the ratio of cyanide-resistant respiration to dark respiration of leaf blade was 38%.イネの暗呼吸の抑制は乾物生産や収量の増大に貢献すると考えられている．エネルギー生産効率の低いシアン耐性呼吸の抑制の可能性を検討するため，酸素同位体分別を利用したシアン耐性呼吸の測定装置を製作し，イネ葉身の測定法を検討した．その結果，葉身の暗呼吸速度はシトクロム経路の阻害剤であるKCN溶液の濃度が10mMのときに，また，シアン耐性呼吸経路の阻害剤であるSHAM溶液の濃度が30mMのときに低下が最大であった．分別係数は３分間10mM KCN溶液に浸漬後HCNに１時間さらした場合に最も高い20.3‰が得られた．いっぽう，SHAM処理では30mMの溶液であれば浸漬法にかかわらず，13.9‰であった．これらから，イネ葉身のオルターティブ酸化酵素とシトクロム酸化酵素の分別係数はそれぞれ20.3‰と13.9‰であると推定され，このときのシアン耐性呼吸の割合は38%であった