Analysis of water in Autonomous Biological Systems (ABS) samples.

Several soluble components, peptidase and amino acids, and carbon isotopic ratio in the water retrieved from flight experiments of Autonomous Biological Systems (ABS) as well as ground control samples are analyzed to interpret the condition, dynamics, material balance of the ABS ecosystems. Organic carbons in flight samples were found to be more abundant compared with the control ones, which suggested the uniform ecosystems in low gravity might easily dissolve more soluble components. The Mir-1997 flight sample showed higher C/N ratio probably because of the dissolution of carbon-rich plant materials.     

The complete sequence of the rice (Oryza sativa) chloroplast genome: intermolecular recombination between distinct tRNA genes accounts for a major plastid DNA inversion during the evolution of the cereals

Summary The entire chloroplast genome of the monocot rice (Oryza sativa) has been sequenced and comprises 134525 bp. Predicted genes have been identified along with open reading frames (ORFs) conserved between rice and the previously sequenced chloroplast genomes, a dicot, tobacco (Nicotiana tabacum), and a liverwort (Marchantia polymorpha). The same complement of 30 tRNA and 4 rRNA genes has been conserved between rice and tobacco. Most ORFs extensively conserved betweenN. tabacum andM. polymorpha are also conserved intact in rice. However, several such ORFs are entirely absent in rice, or present only in severely truncated form. Structural changes are also apparent in the genome relative to tobacco. The inverted repeats, characteristic of chloroplast genome structure, have expanded outward to include several genes present only once per genome in tobacco and liverwort and the large single copy region has undergone a series of inversions which predate the divergence of the cereals. A chimeric tRNA pseudogene overlaps an apparent endpoint of the largest inversion, and a model invoking illegitimate recombination between tRNA genes is proposed which accounts simultaneously for the origin of this pseudogene, the large inversion and the creation of repeated sequences near the inversion endpoints.     

Domains required for nucleic acid binding activities in chloroplast ribonucleoproteins.

Five ribonucleoproteins (or RNA-binding proteins) from tobacco chloroplasts have been identified to date; each of these contains an acidic N-terminal domain (24-64 amino acids) and two conserved RNA-binding domains (82-83 amino acids). All five ribonucleoproteins can bind to ssDNA and dsDNA but show high specificity for poly(G) and poly(U). Here we present the nucleic acid binding activity of each domain using a series of deletion mutant proteins made in vitro from the chloroplast 29 kDa ribonucleoproteins. The acidic domain does not have a positive effect on binding activities and proteins lacking this domain show higher affinities for nucleic acids than the wild-type proteins. Mutant proteins containing single RNA-binding domains can bind to poly(G) and poly(U), though with lower affinities than proteins containing two RNA-binding domains. The spacer region (11-37 amino acids) between the two RNA-binding domains does not interact with poly(G) or poly(U) by itself, but is required for the additive activity of the two RNA-binding domains. Proteins consisting of two RNA-binding domains but lacking the spacer have the same activity as those containing only one RNA-binding domain. Possible roles for each domain in chloroplast ribonucleoproteins are discussed.     

Effect of Supra-High Irradiation on the Photosynthetic System of the Cyanophyte Synechocystis PCC 6714

Stability of thylakoid components under supra-high irradiancewas studied with the cyanophyte Synechocystis PCC 6714. Theactivity of overall photosynthesis was quickly inactivated (T_1/2=20min) under supra-high irradiance (300 W m^–2, white light).In parallel with the inactivation of photosynthesis, QA in PSII was also inactivated. Both inactivations were acceleratedby chloramphenicol (CAP) addition. The reactivation of PS IIrequired weak irradiation and was suppressed by CAP. However,PS I measured as P700 was very stable. The level of PS I measuredas P700 was not significantly reduced by the irradiation for12 h even in the presence of CAP while the level of Cyt b₅₅₉,component of PS II, was decreased markedly. The function ofPS I before and after supra-high irradiation with CAP was examinedby comparing sizes of P700 oxidation induced by a short flash,by a continuous light, and by determination of O₂-and ferredoxin-reduction.No difference was observed in PS I actions before and afterthe irradiation treatment. These results indicate that the PSI complex is very tolerant of supra-high irradiation. However,the cells grown under supra-high irradiance contained much fewerPS I and PS II complexes than Cyt b₆–f complexes. Theformer levels were reduced to a half to one fourth of thosebefore growth while the level of Cyt b₆–f complex wasnot reduced so much. A possible mechanism for changes in thylakoidcomposition under supra-high irradiation was discussed. (Received February 16, 1991; Accepted June 12, 1991)     

Coenzyme A-dependent transacylation system in rabbit liver microsomes

The activities of cofactor-independent and CoA-dependent transacylation were examined for various rabbit tissues. Liver microsomes were found to exhibit relatively high CoA-dependent transacylation activity, while the cofactor-independent transacylation activity was low. The apparent Km values for CoA were 1.4 microM (acceptor, 1-acyl-sn-glycero-3-phosphocholine (1-acyl-GPC] and 3.8 microM (acceptor, 1-acyl-sn-glycero-3-phosphoethanolamine (1-acyl-GPE], respectively. The apparent Vmax values were 2.6 nmol/min/mg (1-acyl-GPC) and 1.2 nmol/min/mg (1-acyl-GPE), respectively. The CoA-dependent transacylation reaction shows a distinct fatty acid specificity. [14C]18:2 and [14C]20:4 at the 2-positions and [14C]18:0 at the 1-positions of donor phospholipids were transferred to lysophospholipids in the presence of CoA. We observed the formation of considerable amounts of acyl-CoA from these fatty acids during the reaction, without the participation of ATP. The transfer of other fatty acids between phospholipids was shown to be almost nil. The very low transfer of 18:1 was in marked contrast to the effective utilization of 18:1-CoA by acyl-CoA:1-acyl-GPC acyltransferase. The effects of several compounds and heat treatment on these two acylation reactions were also examined. The CoA-dependent transacylation reaction may be important for the selective acylation of certain lysophospholipids, such as 1-acyl-GPE, in living cells with the cooperation of acyl-CoA:lysophospholipid acyltransferase, which generates CoA for the former reaction.     

Mycological survey of Korean cereals and production of mycotoxins by Fusarium isolates.

The fungal species isolated from Korean cereals (barley, polished barley, wheat, rye, and malt) were Alternaria spp., Aspergillus spp., Chaetomium spp., Drechslera spp., Epicoccum sp., Fusarium spp., and Penicillium spp., etc. The number of Fusarium strains isolated was 36, and their ability to produce Fusarium mycotoxins on rice was tested. Nivalenol (NIV) was produced by Fusarium graminearum (7 of 9 isolates), Fusarium oxysporum (3 of 10 isolates), and Fusarium spp. (7 of 15 isolates). Of 15 isolates of Fusarium spp., 6 formed deoxynivalenol (DON). Fusarenon-X and 3-acetyl-DON were produced by most NIV- and DON-forming isolates, respectively. Zearalenone was produced by 3 isolates of F. graminearum, 1 isolate of Fusarium equiseti, and 11 isolates of Fusarium spp. T-2 toxin was not produced by any Fusarium isolates. The highest concentrations of mycotoxins produced by Fusarium isolates were 77.4 (NIV), 5.3 (DON), 138.3 (fusarenon-X), 40.6 (3-acetyl-DON), and 23.2 (zearalenone) micrograms/g.     

Photosensitive DNA cleavage and phage inactivation by copper(II)-camptothecin

Upon irradiation with 365-nm light, copper(II)-camptothecin significantly produced single- and double-strand breaks of DNA and also induced a marked inactivation of bacteriophage. The nucleotide sequence analysis exhibited considerably random DNA cleavage. The DNA strand scission by the camptothecin-Cu(II)-UV light system, as well as the phage inactivation, was strongly suppressed by bathocuproine and catalase, indicating participation of cuprous species and hydrogen peroxide in the reaction. The present results suggest that (1) Cu(II) ion may play an important role as a cofactor in antitumor action of camptothecin and (2) the combination of copper-camptothecin plus long-wave ultraviolet light is useful against certain cancer treatment as a new photochemotherapy.     

Effect of Methanol on the Nucleotide Binding to High-Affinity Sites on Chloroplast Coupling Factor 1

The effects of methanol on the nucleotide binding to isolatedchloroplast coupling factor 1 (CF₁) were investigated. IsolatedCF₁ has four kinds of nucleotide binding sites; a barely dissociableADP-binding site (site A), two slowly exchangeable high-affinitysites with different affinities for ADP (sites B and C) whichare not catalytic sites, and several low-affinity sites (Hisaboriand Sakurai 1984). Methanol at 20% (v/v) slightly acceleratedthe binding of ADP to CF₁ but did not influence the number ofbinding sites. Methanol at 10–24% (v/v) affected neitherthe total amounts of bound adenine nucleotides (2.5 mol/molCF₁) nor the incorporation of labeled ADP from the medium (1.5mol/mol CF₁ into the slowly exchangeable sites (sites A, B,C). These results indicate that no appreciable exchange of ADPoccurred at site A at 10–24% (v/v) methanol and excludethe possibility of direct participation of nucleotide bindingat this site in the regulation of ATPase. In 32% methanol, theamount of the labeled ADP bound increased, suggesting some exchangeat site A. Methanol at 20% (v/v) greatly increased the affinitiesof sites B and C for ADP, CDP, GDP, UDP and PP_i. Conformational change of CF₁ induced by the binding of nucleotidesto site(s) B (and C) increased the resistance of CF₁ to inactivationby methanol at high concentrations or by cold treatment. (Received August 16, 1984; Accepted January 23, 1985)