Analysis of expressed sequence tags of flower buds in Lotus japonicus

In order to study gene expression in a reproductive organ, we constructed a cDNA library of mature flower buds in Lotus japonicus, and characterized expressed sequence tags (ESTs) of 842 clones randomly selected. The EST sequences were clustered into 718 non-redundant groups. From BLAST and FASTA search analyses of both protein and DNA databases, 58.5% of the EST groups showed significant sequence similarities to known genes. Several genes encoding these EST clones were identified as pollen-specific genes, such as pectin methylesterase, ascorbate oxidase, and polygalacturonase, and as homologous genes involved in pollen-pistil interaction. Comparison of these EST sequences with those derived from the whole plant of L. japonicus, revealed that 64.8% of EST sequences from the flower buds were not found in EST sequences of the whole plant. Taken together, the EST data from flower buds generated in this study is useful in dissecting gene expression in floral organ of L. japonicus.

Highly divergent sequences of the pollen self-incompatibility (S) gene in class-I S haplotypes of Brassica campestris (syn. rapa) L

Self-incompatibility (SI) enables flowering plants to discriminate between self- and non-self-pollen. In Brassica, SI is controlled by the highly polymorphic S locus. The recently identified male determinant, termed SP11 or SCR, is thought to be the ligand of S receptor kinase, the female determinant. To examine functional and evolutionary properties of SP11, we cloned 14 alleles from class-I S haplotypes of Brassica campestris and carried out sequence analyses. The sequences of mature SP11 proteins are highly divergent, except for the presence of conserved cysteines. The phylogenetic trees suggest possible co-evolution of the genes encoding the male and female determinants.

Agrobacterium-mediated transformation of cotyledonary explants of Chinese cabbage (Brassica campestris L. ssp. pekinensis)

 A procedure for producing transgenic Chinese cabbage plants by inoculating cotyledonary explants with Agrobacterium tumefaciens strain EHA101 carrying a binary vector pIG121Hm, which contains kanamycin-resistance and hygromycin-resistance genes and the GUS reporter gene, is described. Infection was most effective (highest infection frequency) when explants were infected with Agrobacterium for 15 min and co-cultivated for 3 days in co-cultivation medium at pH 5.2 supplemented with 10 mg/l acetosyringone. Transgenic plants of all three cultivars used were obtained with frequencies of 1.6-2.7% when the explants were regenerated in shoot regeneration medium solidified with 1.6% agar. A histochemical GUS assay and PCR and Southern blot analyses confirmed that transformation had occurred. Genetic analysis of T1 progeny showed that the transgenes were inherited in a Mendelian fashion.

Impact of elevated cytosolic and apoplastic invertase activity on carbon metabolism during potato tuber development

During tuberization in Solanum tuberosum var. Desirée maximal catalytic activities of invertase(s) and sucrose synthase are inversely correlated. During the early stages, invertase activity is high and declines during maturation. The decrease in invertase activity is accompanied by a decrease in the hexose to sucrose ratio and an increase in sucrose synthase activity. This switch is paralleled by the onset of the storage phase as shown by the accumulation of starch and storage proteins. Biochemical and genetic evidence suggests that sucrose synthase activity is positively correlated with sink strength. To explore the possibility of enhancing sink strength in potato tubers by elevating the sucrolytic capacity, transgenic potato plants expressing either cytosolic or apoplastic yeast invertase in their tubers were made. Surprisingly, cytosolic invertase led to a decrease and apoplastic invertase to an increase in tuber yield. To understand the causes of the observed phenotypes, carbon metabolism in tubers of transgenic and control plants was analysed during different stages of tuber development. Both cytosolic and apoplastic invertase resulted in decreased sucrose and elevated glucose contents, indicating that sucrose is accessible in both compartments. Metabolic perturbation, however, was found to be compartment specific. Elevated cytosolic invertase activity led to increased carbon flux towards glycolysis and accumulation of phosphorylated intermediates. The phosphorylated intermediates were not used to build up starch. In contrast, apoplastic invertase does not lead to a significant increase in hexose phosphates compared to untransformed controls. Thus, hexoses originating in the apoplast are not efficiently phosphorylated during potato tuber development, which might be explained by an endocytotic uptake of sucrose and/or hexoses from the apoplast into the vacuole bypassing the cytosolic compartment.

QSAR and molecular graphics analysis of N2-phenylguanines as inhibitors of herpes simplex virus thymidine kinases

A quantitative structure-activity relationship study of N2-(substituted)-phenylguanines (PHG) as inhibitors of herpes simplex virus thymidine kinase (HSV TK) was performed. The activity of a set of PHG derivatives were analyzed against the thymidine kinase of herpes simplex virus types 1 (HSV1 TK) and 2 (HSV2 TK). Classic and calculated physicochemical parameters were included in the analysis. The results showed that there is an important difference in the activity of the meta substituted PHG derivatives against HSV1 TK and HSV2 TK. The activity of the meta derivatives against HSV2 TK is influenced by a steric effect, which is not observed against HSV1 TK. The superposition of the three-dimensional structures of the active sites of HSV1 TK (crystal structure) and HSV2 TK (homology model) revealed that the amino acid Ile97 is located near the meta position in the HSV1 TK active site, whereas the amino acid Leu97 is located near the meta position in the HSV2 TK active site. This single difference in the active sites of both enzymes can explain the source of the steric effect and serves as an indication that our previously proposed binding mode for the PHG derivatives is plausible. However, another observed mutation in the active site region, Ala168 by Ser168, suggests that an alternative binding mode, similar to that of ganciclovir, could be possible.

Distribution and physiological characteristics of hyperthermophiles in the Kubiki oil reservoir in Niigata, Japan

The distribution of culturable hyperthermophiles was studied in relation to environmental conditions in the Kubiki oil reservoir in Japan, where the temperature was between 50 and 58 degrees C. Dominant hyperthermophilic cocci and rods were isolated and shown to belong to the genera Thermococcus and Thermotoga, respectively, by 16S rDNA analyses. Using the most-probable-number method, we found that hyperthermophilic cocci were widely distributed in several unconnected fault blocks in the Kubiki oil reservoir. In 1996 to 1997, their populations in the production waters from oil wells were 9.2 x 10(3) to 4.6 x 10(4) cells/ml, or 10 to 42% of total cocci. On the other hand, hyperthermophilic rods were found in only one fault block of the reservoir with populations less than 10 cells/ml. Dominant Thermococcus and Thermotoga spp. grew at reservoir temperatures and utilized amino acids and sugars, respectively, as sole carbon sources. While organic carbon was plentiful in the environment, these hyperthermophiles were unable to grow in the formation water due to lack of essential nutrients. Concentrations of some organic and inorganic substances differed among fault blocks, indicating that the movement of formation water between fault blocks was restricted. This finding suggests that the supply of nutrients via fluid current is limited in this subterranean environment and that the organisms are starved in the oil reservoir. Under starved conditions at 50 degrees C, culturable cells of Thermococcus sp. remained around the initial cell density for about 200 days, while those of Thermotoga sp. decreased exponentially to 0. 01% of the initial cell density after incubation for the same period. The difference in survivability between these two hyperthermophiles seems to reflect their populations in the fault blocks. These results indicate that hyperthermophilic cocci and rods adapt to the subterranean environment of the Kubiki oil reservoir by developing an ability to survive under starved conditions.

Regulation of carbohydrate partitioning during the interaction of potato virus Y with tobacco

Abstract To test whether carbohydrates may play a signalling function during plant pathogenesis, we investigated the interaction between tobacco and potato virus Y (PVY(N)). Four days after PVY(N) infection, leaves started to accumulate soluble sugars and leaf photosynthesis decreased. The accumulation of soluble sugars was accompanied by an induction of cell wall invertase and a gradual decrease in the sucrose-to-hexose ratio. In parallel to changes in carbohydrate metabolism and photosynthesis, transcripts encoding PR-proteins accumulated. Based on this coincidence, it was hypothesized that elevated hexose levels may enhance the expression of defence-related functions and might possibly explain the phenomenon of high sugar resistance in plants. This notion has been supported by the fact that cell wall invertase-expressing transgenic tobacco plants were found to be resistant against PVY(N) (Herbers et al., 1996b). To exclude the possibility that salicylate, which accumulates in plants expressing invertase, may be responsible for the observed resistance, these transgenic plants were crossed with salicylate hydroxylase-expressing plants (nahG). The progeny were selected for high levels of sugar and low levels of salicylate. Necrotic lesions also developed, typically formed on the leaves of plants expressing invertase, and transcripts encoding PR-Q accumulated in the absence of salicylate. On the other hand, accumulation of PR-1b transcripts decreased, indicating that sugars are not sufficient for PR-1b induction. Infection experiments using these plants as hosts revealed resistance towards PVY(N). Thus, the mechanism of apoplastic invertase induced virus resistance is salicylate independent and most likely sugar mediated.

Structure-activity relationship studies of carcinogenic activity of polycyclic aromatic hydrocarbons using calculated molecular descriptors with principal component analysis and neural network methods

Recently a new methodology based on local density of state (LDOS) calculations using topological and semiempirical methods was proposed to identify the carcinogenic activity of polycyclic aromatic hydrocarbons (PAHs). In this work we perform a comparative study of this methodology with principal component analysis (PCA) and neural networks (NN). The PCA and NN results show that LDOS quantum chemical descriptors are relevant descriptors to identify the carcinogenic activity of methylated and non-methylated PAHs. Also, we show that the combination of these distinct methodologies can be an efficient and powerful tool in the structure-activity studies of PAHs compounds. We have studied 81 methylated and non-methylated PAHs, and our study shows that with the use of these methods it is possible to correctly predict the carcinogenic activity of PAHs with accuracy higher than 80%.

Medium and genotype factors influencing shoot regeneration from cotyledonary explants of Chinese cabbage (Brassica campestris L. ssp. pekinensis)

Medium conditions for reliable shoot regeneration from cotyledonary explants of Chinese cabbage were examined. Maximum shoot regeneration was obtained in the presence of 5 mg/l BA and 0.5 mg/l NAA. Shoot induction was further improved by the addition of AgNO₃ as well as higher concentrations (1.2-1.6%) of agar in the regeneration medium. When 123 genotypes were tested, a large variation in regeneration frequency was observed, ranging from 95% to 0%. Shoot regeneration frequency was not related to origin and days to maturity of the genotypes. Ethylene production from cultured explants seemed to play an important role in shoot regeneration. Explants of highly responsive genotypes or if cultured on the medium solidified with a higher concentration of agar generally showed low levels of ethylene production. However, AgNO₃, which also enhanced shoot induction, resulted in an increase in ethylene production. The possible interaction between ethylene and shoot regeneration is discussed.

Method for the preparation of restricted access media by low-temperature plasma treatment

A new method for the preparation of restricted access media (RAM) was developed. A low-temperature plasma treatment removed octadecyl groups on the external surface of octadecylsilylated silica gel before those on the internal surface to produce silanol groups. The silanol groups produced were glycerylpropylsilylated to give RAM, DIOL-ODSs, consisting of internal octadecyl groups and external glycerylpropyl groups. DIOL-ODSs were inert to serum proteins and retained low-molecular-mass analytes adequately. Direct injection analysis of anticonvulsants in serum was accurately performed by column-switching high-performance liquid chromatography using a pre-column packed with DIOL-ODS.

Prediction of the binding mode of N2-phenylguanine derivative inhibitors to herpes simplex virus type 1 thymidine kinase

The probable binding mode of the herpes simplex virus thymidine kinase (HSV1 TK) N2-[substituted]-phenylguanine inhibitors is proposed. A computational experiment was designed to check some qualitative binding parameters and to calculate the interaction binding energies of alternative binding modes of N2-phenylguanines. The known binding modes of the HSV1 TK natural substrate deoxythymidine and one of its competitive inhibitors ganciclovir were used as templates. Both the qualitative and quantitative parts of the computational experiment indicated that the N2-phenylguanine derivatives bind to the HSV1 TK active site in the deoxythymidine-like binding mode. An experimental observation that N2-phenylguanosine derivatives are not phosphorylated during the interaction with the HSV1 TK gives support to the proposed binding mode.

Scanning electron microscopy of microspore embryogenesis inBrassica spp

Scanning electron microscopy was employed to study and compare microspore embryogenesis in vitro with pollen development in planta inBrassica napus andB. oleracea. An exine with its specific pattern had already been formed, when microspores were released from tetrads. During subsequent pollen development, microspores increased in size and continued to strengthen the exine. Upon in vitro culture, all microspores, i.e., embryogenic and nonembryogenic, initially showed the same morphological features. After 24 h in culture, the microspores had increased in size. Thereafter, embryogenesis was indicated in some microspores by two different morphological changes. One featured an expansion in volume of the cell cluster around the germination aperture (type I), the other showed cell cluster volume expansion over the entire microspore surface (type II). Two-thirds of embryogenic microspores in bothB. napus andB. oleracea demonstrated type I development. When followed by fluorescence microscopy, in vitro culture of microspores revealed cultures with a high embryo frequency were those with a high frequency of symmetrical division.

Microspore culture of radish (Raphanus sativus L.): influence of genotype and culture conditions on embryogenesis

A number of factors influencing embryogenesis from isolated microspores of radish (Raphanus sativus) were examined. Of 11 genotypes evaluated, six produced embryos ranging from 8.3 embryos per 10(5) microspores for 'Chugoku-ao' to 0.2 for 'Tenshun', but five genotypes were not responsive. An initial culture period at elevated temperature before incubation at 25°C was essential for induction of microspore embryogenesis. However, the optimum period of the treatment varied among genotypes and/or experiments. Bud size also influenced microspore embryogenesis. Though optimum bud size was different between genotypes, the microspore populations represented in these buds contained uninucleate and binucleate microspores. Selection of embryogenic microspores using percoll density gradient resulted in up to 1.3-fold increase of embryo yield. Though almost all embryos failed to develop directly into plantlets, plants were obtained by multiple subcultures. The regenerated plants had hyperploid chromosome numbers.

Polyethylene glycol-modified avidin: a novel agent for the selective extraction of biotinylated immune-complex in an aqueous two-phase system

Chicken avidin was chemically modified with 2,4-bis[O-methoxypoly(ethylene glycol)]-6-chloro-s-triazine (activated PEG2) to form PEG-avidin. The PEG-avidin, in which 78% of the amino groups were modified, retained 49% of the active biotin-binding sites. The modified avidin was partitioned preferentially into the PEG-phase in an aqueous two-phase system (PEG/dextran). Using PEG-avidin, the immune-complex formed between biotinylated anti-mouse IgG and its antigen IgG (mouse) molecules, was successfully transferred into the PEG-phase in an aqueous two-phase system. This finding leads to the effective isolation of a specific antigen among various kinds of antigens by partitioning with a two-phase system using PEG-avidin.

Synthesis, properties and microbiological activity of hydrophobic derivatives of vitamin B12

Long chain alkylcobalamins and long chain acyl-cyanocobalamins, two types of hydrophobic derivatives of vitamin B12, were synthesized. It was shown by TLC and determination of the partition coefficient between organic and aqueous phases that the hydrophobicity of alkylcobalamins and acyl-cyanocobalamins increased with the chain length of the alkyl or acyl group introduced into cobalamin. Long chain alkylcobalamins were easily converted to aquacobalamin by photoirradiation, but the first-order rate constant of photolysis decreased with the length of an alkyl group. Long chain acyl-cyanocobalamins were gradually hydrolyzed to cyanocobalamin in neutral or alkaline solution with the pseudo-first order rate constant increasing with the pH of the solution. Stabilization of acyl-cyanocobalamins toward hydrolysis was achieved by introducing a methyl group into the alpha-position of an acyl group. All the long chain alkylcobalamins tested supported the growth of Escherichia coli 215, a cobalamin- or L-methionine-auxotroph, and Lactobacillus leichmannii, although their activity as cobalamin was at most 28% and 15% that of cyanocobalamin for E. coli 215 and L. leichmannii, respectively.

Effect of genotype on shoot regeneration from cotyledonary explants of rapeseed (Brassica napus L.)

Ability of shoot regeneration from cotyledonary explants of rapeseed (B. napus) was surveyed for 100 cultivars. Effects of explant age and plant growth regulators were determined before screening the genotypes. The optimal condition required 4-day-old cotyledons as explant and 4.0 mg/l benzylaminopurine as plant growth regulator. Gas-permeable tape as sealing material was more effective for shoot regeneration than Parafilm. When testing cultivars, shoot regeneration response was strongly influenced by genotype with a range of variation from 97% (percentage of explants regenerating shoots) in 'Arabella' and 'Norin 26' to 0% in 'Norin 18' and 'Norin 30'. The response was not dependent on origin and cropping type (spring vs. winter type). The ability of shoot regeneration was not related to that of microspore embryogenesis. The regenerants rooted on medium containing 2.0 mg/l indole-3-butyric acid and after planting in soil flowered and set seeds. Histological studies showed that shoot meristems developed in callus which had grown from the vascular bundle tissue within 8 days.

Quantitative structure-activity relationships for 1,4-dihydropyridine calcium channel antagonists (nifedipine analogues): a quantum chemical/classical approach

A quantum chemical (AM1) combined with a classical study of structure-activity relationships for 1,4-dihydropyridines (nifedipine analogues) was performed. The biological data were taken from the literature. The quantum chemical parameters tested were energies of HOMO and LUMO, dipole moment (total and partial), hardness, Mulliken electronegativity, frontier orbital indices, and others. Also tested were classical parameters like Hansch hydrophobic constant, tau; Hammett electronic constant for the meta position, sigma m; and the Verloop sterimol parameters, B1 and L. The van der Waals volume was also tested. The pharmacological activities of the para monoderivatives are negatively correlated with the molecular volume, i.e. a steric factor. The meta position of the phenyl ring is affected by steric and electronic parameters, whereas the ortho position seems to be affected by hydrophobic and electronic parameters.