Protective effects of melatonin against low- and high-LET irradiation

To investigate the protective effects of melatonin against high-LET ionizing radiation, V79 Chinese hamster cells were irradiated with 100 keV/mu m carbon beam. Parallel experiments were performed with 200 kV X-rays. To avoid the impact from extra solvents, melatonin was dissolved directly in culture medium. Cells were cultured in melatonin medium for 1 hr before irradiation. Cell inactivation was measured with conventional colony forming assay, medium containing 6-thioguanine was used for the selection of mutants at hprt locus, and the cell cycle was monitored by flow cytometry. Both carbon beam and X-rays induced cell inactivation, hprt gene mutation and cell cycle G2 block dose-dependently. But carbon beam showed stronger effects as indicated by all three endpoints and the relative biological effectiveness (RBE) was 3.5 for cell killing (at 10% survival level) and 2.9 for mutation induction (at 5 x 10(-5) mutants/ cell level). Melatonin showed protective effects against ionizing radiation in a dose-dependent manner. In terms of cell killing, melatonin only increased the survival level of those samples exposed to 8Gy or larger of X-rays or 6 Gy or larger of carbon beam. In the induction of hprt mutation and G2 block, melatonin reduced such effects induced by carbon beam but not by X-rays. The results suggest that melatonin reduces the direct interaction of particles with cells rather than an indirect interaction. Further studies are required to disclose the underlying mechanisms.

Effects of ion beam irradiation on adventitious shoot regeneration from in vitro leaf explants of Saintpaulia ionahta

The effects of 960 MeV carbon ion beam and 8 MeV X-ray irradiation on adventitious shoots from in vitro leaf explants of two different Saintpaulia ionahta (Mauve and Indikon) cultivars were studied with regard to tissue increase, shoots differentiation and morphology changes in the shoots. The experimental results showed that the survival fraction of shoot formation for the Mauve and Indikon irradiated with the carbon ion beam at 20 Gy were 0.715 and 0.600, respectively, while those for both the cultivars exposed to the Xray irradiation at the same dose were 1.000. Relative biological effectiveness (RBE) of Mauve with respect to X-ray was about two. Secondly, the percentage of regenerating explants with malformed shoots in all Mauve regenerating explants irradiated with carbon ion beam at 20 Gy accounted for 49.6%, while that irradiated with the same dose of X-ray irradiation was only 4.7%; as for Saintpatdia ionahta Indikon irradiated with 20 Gy carbon ion beam, the percentage was 43.3%, which was higher than that of X-ray irradiation. Last, many chlorophyll deficient and other varieties of mutants were obtained in this study. Based on the results above, it can be concluded that the effect of mutation induction by carbon ion beam irradiation on the leaf explants of Saintpaulia ionahta is better than that by X-ray irradiation; and the optimal mutagenic dose varies from 20 Gy to 25 Gy for carbon ion beam irradiation.

Effect of gamma-ray radiation on physiological, morphological characters and chromosome aberrations of minitubers in Solanum tuberosum L.

Purpose: To investigate the effects of gamma-ray radiation on the physiological, morphological characters and chromosome aberrations of minitubers. Materials and methods: Minitubers of one potato cultivar, 'Shepody', were irradiated with 8 doses of gamma-rays (0, 10, 20, 30, 40, 50, 60, 70 and 80 Gy [Gray]) to investigate the effects of radiation on emergence ability, plant height and root length, morphological variations, chromosome aberrations, M-1 (first generation mutants) tuber number and size of minituber plants. Results: Compared with the non-irradiated controls, the whole period of emergence was prolonged by 10-15 days for minitubers treated with gamma-ray radiation, but low doses of radiation (10, 20 and 30 Gy) promoted the emergence percentage of minitubers. With an increase in radiation dose, the emergence percentage, plant height and root length of minituber plants were significantly inhibited at 40 and 50 Gy. No emergence occurred at 60 Gy and higher doses. After radiation, a series of morphological variations and chromosome aberrations appeared in minituber plants. Radiation with 20 Gy promoted tuber formation, and the average number and diameter of M-1 tubers per plant were significantly increased over the control by 71% and 34%, respectively. Conclusion: Low doses of radiation (10-30 Gy) might be used as a valuable parameter to study the improvement of minitubers by gamma-ray radiation treatment.

关于牧草辐射育种几个问题的探讨

本文以牧草为材料 ,阐述了辐射敏感性的类型划分方法。将异花授粉牧草沙打旺辐照当代的种子直接播种在≥ 1 0℃ (年积温 2 3 0 8℃ )的低温下 ,提高了突变体的适应性 ,增加了选择的准确性 ,缩短了育种周期 ;M1代产生了显性早熟突变 ,M2 代有 2 7 2 %的植株保持早熟 ,比对照早开花 1 6～ 5 1d ,但仍有分离 ;5年育成彭阳早熟沙打旺 ,能在≥ 1 0℃ (年积温 1 847℃ )的地区开花结籽 ;播种当年始花序着生叶位与出苗至开花天数、株高和一级分枝呈极显著正相关。选育产草量高且早熟的沙打旺新品种 ,始花序叶位以在 9～ 1 0个为宜

Attenuation of Edwardsiella tarda Virulence by Small Peptides That Interfere with LuxS/Autoinducer Type 2 Quorum Sensing

Edwardsiella tarda is a gram-negative pathogen with a broad host range that includes humans, animals, and fish. Recent studies have shown that the LuxS/autoinducer type 2 (AI-2) quorum sensing system is involved in the virulence of E. tarda. In the present study, it was found that the E. tarda LuxS mutants bearing deletions of the catalytic site (C site) and the tyrosine kinase phosphorylation site, respectively, are functionally inactive and that these dysfunctional mutants can interfere with the activity of the wild-type LuxS. Two small peptides, 5411 and 5906, which share sequence identities with the C site of LuxS, were identified. 5411 and 5906 proved to be inhibitors of AI-2 activity and could vitiate the infectivity of the pathogenic E. tarda strain TX1. The inhibitory effect of 5411 and 5906 on AI-2 activity is exerted on LuxS, with which these peptides specifically interact. The expression of 5411 and 5906 in TX1 has multiple effects (altering biofilm production and the expression of certain virulence-associated genes), which are similar to those caused by interruption of luxS expression. Further study found that it is very likely that 5411 and 5906 can be released from the strains expressing them and, should TX1 be in the vicinity, captured by TX1. Based on this observation, a constitutive 5411 producer (Pseudomonas sp. strain FP3/pT5411) was constructed in the form of a fish commensal isolate that expresses 5411 from a plasmid source. The presence of FP3/pT5411 in fish attenuates the virulence of TX1. Finally, it was demonstrated that fish expressing 5411 directly from tissues exhibit enhanced resistance against TX1 infection.

Attenuation of Edwardsiella tarda Virulence by Small Peptides That Interfere with LuxS/Autoinducer Type 2 Quorum Sensing

Edwardsiella tarda is a gram-negative pathogen with a broad host range that includes humans, animals, and fish. Recent studies have shown that the LuxS/autoinducer type 2 (AI-2) quorum sensing system is involved in the virulence of E. tarda. In the present study, it was found that the E. tarda LuxS mutants bearing deletions of the catalytic site (C site) and the tyrosine kinase phosphorylation site, respectively, are functionally inactive and that these dysfunctional mutants can interfere with the activity of the wild-type LuxS. Two small peptides, 5411 and 5906, which share sequence identities with the C site of LuxS, were identified. 5411 and 5906 proved to be inhibitors of AI-2 activity and could vitiate the infectivity of the pathogenic E. tarda strain TX1. The inhibitory effect of 5411 and 5906 on AI-2 activity is exerted on LuxS, with which these peptides specifically interact. The expression of 5411 and 5906 in TX1 has multiple effects (altering biofilm production and the expression of certain virulence-associated genes), which are similar to those caused by interruption of luxS expression. Further study found that it is very likely that 5411 and 5906 can be released from the strains expressing them and, should TX1 be in the vicinity, captured by TX1. Based on this observation, a constitutive 5411 producer (Pseudomonas sp. strain FP3/pT5411) was constructed in the form of a fish commensal isolate that expresses 5411 from a plasmid source. The presence of FP3/pT5411 in fish attenuates the virulence of TX1. Finally, it was demonstrated that fish expressing 5411 directly from tissues exhibit enhanced resistance against TX1 infection.

Screening of genes expressed in vivo after infection by Vibrio anguillarum M3

Aims: Genes uniquely expressed in vivo may contribute to the overall pathogenicity of an organism and are likely to serve as potential targets for the development of new vaccine. This study aims to screen the genes expressed in vivo after Vibrio anguillarum infection by in vivo-induced antigen technology (IVIAT). Methods and Results: The convalescent-phase sera were obtained from turbot (Scophthalmus maximus) survived after infection by the virulent V. anguillarum M3. The pooled sera were thoroughly adsorbed with M3 cells and Escherichia coli BL21 (DE3) cells. A genomic expression library of M3 was constructed and screened for the identification of immunogenic proteins by colony immunoblot analysis with the adsorbed sera. After three rounds of screening, 19 putative in vivo-induced (ivi) genes were obtained. These ivi genes were catalogued into four functional groups: regulator/signalling, metabolism, biological process and hypothetical proteins. Three ivi genes were insertion-mutated, and the growth and 50% lethal dose (LD50) of these mutants were evaluated. Conclusions: The identification of ivi genes in V. anguillarum M3 sheds light on understanding the bacterial pathogenesis and provides novel targets for the development of new vaccines and diagnostic reagents. Significance and Impact of the Study: To the best of our knowledge, this is the first report describing in vivo-expressed genes of V. anguillarum using IVIAT. The screened ivi genes in this study could be new virulent factors and targets for the development of vaccine, which may have implications for the development of diagnostic regents.

Screening of genes expressed in vivo after infection by Vibrio anguillarum M3

Aims: Genes uniquely expressed in vivo may contribute to the overall pathogenicity of an organism and are likely to serve as potential targets for the development of new vaccine. This study aims to screen the genes expressed in vivo after Vibrio anguillarum infection by in vivo-induced antigen technology (IVIAT). Methods and Results: The convalescent-phase sera were obtained from turbot (Scophthalmus maximus) survived after infection by the virulent V. anguillarum M3. The pooled sera were thoroughly adsorbed with M3 cells and Escherichia coli BL21 (DE3) cells. A genomic expression library of M3 was constructed and screened for the identification of immunogenic proteins by colony immunoblot analysis with the adsorbed sera. After three rounds of screening, 19 putative in vivo-induced (ivi) genes were obtained. These ivi genes were catalogued into four functional groups: regulator/signalling, metabolism, biological process and hypothetical proteins. Three ivi genes were insertion-mutated, and the growth and 50% lethal dose (LD50) of these mutants were evaluated. Conclusions: The identification of ivi genes in V. anguillarum M3 sheds light on understanding the bacterial pathogenesis and provides novel targets for the development of new vaccines and diagnostic reagents. Significance and Impact of the Study: To the best of our knowledge, this is the first report describing in vivo-expressed genes of V. anguillarum using IVIAT. The screened ivi genes in this study could be new virulent factors and targets for the development of vaccine, which may have implications for the development of diagnostic regents.

Functional characterization of sll0659 from Synechocystis sp PCC 6803

Synchocystis sp. PCC 6803 lacks a gene for the any known types of lycopene cyclase. Recently, we reported that sll0659 (unknown for its function) from Synechocystis sp. PCC6803 shows similarity in sequence to a lycopene cyclase gene-CruA from Chlorobium tepidum. To test, whether Sll0659 encoded protein serves as lycopene cyclase, in this study, we investigated the carotenoids of the wild types ans mutants, In the sll0659 deleted mutant, there is no blockage at the lycopene cyclization step. Our results demonstrate that sll0659 does not affect lycopene cyclization. However, the ultrastructure of mutants suggests the involvement or necessity of sll0659 in the cell division.

Induction and characterization of green pigmentation mutant in Porphyra yezoensis Ueda

The free living conchocelis of Porphyra yezoensis Ueda was treated with N-methyl-N-nitro-N-nitrosoguanidine to induce pigmentation mutants. The artificial green pigmentation mutant of P. yezoensis conchocelis, which was composed entirely of green cells, was isolated through visualization with the unaided eye. The acquired green conchocelis was further developed into a green gametophytic blade. This mutant was relatively stable in color in both gametophytic blade and conchocelis phases. The gametophytic blade mutant was successively cultivated for commerce at some Porphyra farms in Rudong, China, and few wild type or sectorially variegated gametophytic blade occurred, indicating that the green mutant has commercial value. The green mutant was characterized as having lower phycoerythrin and higher phycocyanin content, and SDS-PAGE suggested that phycoerythrin was missing the gamma-subunit in comparison to the wild type. The wild type and the green mutant showed a clear difference in 02 evolution rates in white, green, yellow, and red light, which might be due to the qualitative and quantitative changes of phycoerythrin, and the quantitative difference of phycocyanin. (C) 2008 Elsevier B.V. All rights reserved.

Construction and characterization of a live, attenuated esrB mutant of Edwardsiella tarda and its potential as a vaccine against the haemorrhagic septicaemia in turbot, Scophthamus maximus (L.)

The esrB gene of Edwardsiella tarda, which encodes a regulator protein of the type III secretion system, was mutated by the unmarked deletion method and reintroduced by allelic exchange into the chromosome of E. tarda LSE40 by means of the suicide vector pRE 112. The LSE40 esrB mutant was highly attenuated when inoculated intraperitoneally into turbot Scophthamus maximus L., showing a 50% lethal dose of 10(8.1) cfu/fish. The esrB mutants were not recoverable from the internal organs at 14 days post-inoculation. Vaccination with a single dose of 10(5)-10(7) cfu/fish of the esrB mutant elicited significant protection against the wildtype strain of E. tarda LSE40 (relative percentage survival > 50%). The protection correlated well with the antibody titres in the serum of vaccinated fish. (c) 2006 Elsevier Ltd. All rights reserved.

Functional genomic hypothesis generation and experimentation by a robot scientist

King R. D., Whelan, K. E., Jones, F. M., Reiser, P. G. K., Bryant, C. H., Muggleton, S., Kell, D. B. and Oliver, S. G. (2004) Functional genomic hypothesis generation and experimentation by a robot scientist. Nature 427 (6971) p247-252

Ethylene rapidly up-regulates the activities of both monomeric GTP-binding proteins and protein kinase(s) in epicotyls of pea

Igor E. Moshkov, Galina V. Novikova, Luis A.J. Mur, Aileen R. Smith, and Michael A. Hall. (2003). Ethylene rapidly up-regulates the activities of both monomeric GTP-binding proteins and protein kinase(s) in epicotyls of pea. Plant Physiology, 131(4), 1718-1726 RAE2008

Salicylic acid dependent signaling promotes basal thermotolerance but is not essential for acquired thermotolerance in Arabidopsis thaliana

Clarke, S. M., Mur, L. A. J., Wood, J. E., & Scott, I. M. (2004). Salicylic acid dependent signaling promotes basal thermotolerance but is not essential for acquired thermotolerance in Arabidopsis thaliana. The Plant Journal, 38(3), 432-447. Sponsorship: BBSRC RAE2008

Salicylate accumulation inhibits growth at chilling temperature in Arabidopsis

Ian M. Scott, Shannon M. Clarke, Jacqueline E. Wood and Luis A.J. Mur (2004). Salicylate accumulation inhibits growth at chilling temperature in Arabidopsis. Plant Physiology, 135(2), 1040-1049. RAE2008