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Cloning and functional analysis of the sequences flanking mini-Tn5 in the magnetosomes deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1

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Science China(Life Sciences) 2005年第6期48卷 574-584页

作者： LI Feng1,2, LI Ying1, JIANG Wei1, WANG Zhenfang1 & LI Jilun1 1. State Key Laboratory for Agro-biotechnology and Department of Microbiology, China Agricultural University, Beijing 100094, China 2. Department of Biology, Huaibei Coal Industry Teachers’ College, Huaibei 235000, China 1. State Key Laboratory for Agro-biotechnology and Department of Microbiology China Agricultural University 100094 Beijing China 2. Department of Biology Huaibei Coal Industry Teachers’ College 235000 Huaibei China

A magnetosome deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1 was generated by mini-Tn5 transposon mutagenesis, and a 5045-bp fragment flanking mini-Tn5 in NM4 was cloned by Anchored PCR. Sequencing analysis showed that this fragment involved six putative open reading frames (ORFs); the mini-Tn5 was inserted into ORF4. Functional complementary test indicated that the 5045-bp fragment was required for biosynthesis of mag-netosomes in M. gryphiswaldense MSR-1. The protein encoded by ORF4 had 25% of identity with the chemotaxis protein CheYIII of Caulobacter crescentus CB15, and the protein encoded by ORF4 contained a conserved signal receiver domain that can receive the signal from the sensor partner of the bacterial two-component systems. It was suggested that the protein en-coded by ORF4 may take part in the signal transduction relating to biosynthesis of magneto-somes.

关键词： Magnetospirillum gryphiswaldense, magnetosome deleted mutant, gene cloning, functional analysis.

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Analyzing the H19-and T65-epitopes in 38 kd phosphory-lated protein of Marek's disease viruses and comparing chicken immunological reactions to viruses point-mutated in the epitopes

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Science China(Life Sciences) 2004年第1期47卷 82-91页

作者： Lee Lucy F Avian Disease and Oncology Laboratory East Lansing Ml 48823 USA

DNA sequencing analysis in 38 kd phosphorylated protein (pp38) ORF of Marek's disease viruses (MDV) indicated that all tested 10 virulent strains with different pathotypes had 'A' at base #320 and glutamine at aa#107 while reacted with monoclonal antibody (Mab) H19 in indirect fluorescence antibody test (IFA). However, vaccine strain CVI988 had 'G' at base#320 and arginine at aa#107 instead, when it was negative in IFA with Mab H19. Some strains were also reactive with Mab T65 in IFA while there was 'G' at base #326 and glycine at aa#109, but the other strains, which had 'A' at base #326 and glutamic acid at aa#109, did not react with Mab T65. By comparison of CVI988 to its point mutants CVI/rpp38(AG) and CVI/rpp38(AA) with 1 or 2 base(s) changes at bases #320 and /or #326 of pp38 gene for their reactivity with Mab H19 and T65, it was confirmed that the glutamine at aa#107 and glycine at aa#109 were critical to epitopes H19 and T65 respectively. Immuno-reactions to MDV were compared in SPF chickens inoculated with cloned CVI988 and its mutant CVI/rpp38(AG). It was found that antibody responses to MDV in chickens inoculated with CVI/rpp38(AG) were delayed and significantly lower than that in chickens inoculated with the native CVI988. By differential comparison of antibody titers to different antigens, a third epitope specific to CVI988 and dependent on arginine at aa#107 was suggested to be responsible for the big difference in antibody responses induced by native CVI988 and its mutant.

关键词： Marek's disease virus, pp38 gene, point mutant, epitopes, antibody responses.

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Thermostability of photosynthesis in two new chlorophyll b-less rice mutants

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Science China(Life Sciences) 2005年第2期48卷 139-147页

作者： LIN Zhifang1,PENG Changlian1,Xu Xinlan1,LIN Guizhu 1 & ZHANG Jingliu2 1.South China Institute of Botany,Chinese Academy of Sciences,Guangdong Key Laboratory of Digital Botanical Garden,Guangzhou 510650,China 2.National Key Laboratory of Plant Molecular Genetics,Institute of Plant Physiology & Ecology,Shanghai Institutes of Biological Sci- ences,Chinese Academy of Sciences,Shanghai 200032,China 1. South China Institute of Botany Chinese Academy of Sciences Guangdong Key Laboratory of Digital Botanical Garden 510650 Guangzhou China 2. National Key Laboratory of Plant Molecular Genetics Institute of Plant Physiology & Ecology Shanghai Institutes of Biological Sciences Chinese Academy of Sciences 200032 Shanghai China

Leaves of the two new chlorophyll b-less rice mutants VG28-1, VG30-5 and the wild type rice cv. Zhonghua 11 were subjected to temperatures 28, 36, 40, 44 and 48℃ in the dark for 30 min or gradually elevated temperature from 30℃ to 80℃ at 0.5℃/min. The thermostability of photosynthetic apparatus was estimated by the changes in chlorophyll fluorescence parameters, photosynthetic rate and pigment content, chloroplast ultrastructure and tissue location of H2O2 accumulation. There were different patterns of Fo-temperature curves between the Chl b-less mutants and the wild type plant, and the temperature of Fo rising threshold was shifted 3℃ lower in the Chl b-less mutants (48℃) than in the wild type (51℃). At temperature up to about 45℃, chloroplasts were swollen and thylakoid grana became misty accompanied with the complete loss of photosynthetic oxygen evolution in the two Chl b-less mutants, but chloroplast ultrastruc- ture in the wild type showed no obvious alteration. After 55℃ exposure, the disordered thylakoid and significant H2O2 accumulation in leaves were found in the two Chl b-less mutants, whereas in the wild type plant, less H2O2 was accumulated and the swollen thylakoid still maintained a cer- tain extent of stacking. A large extent of the changes in qP, NPQ and Fv/Fm was consistent with the Pn decreasing rate in the Chl b-less mutants during high temperature treatment as compared with the wild type. The results indicated that the Chl b-less mutants showed a tendency for higher thermosensitivity, and loss of Chl b in LHC II could lead to less thermostability of PSII structure and function. Heat damage to photosynthetic apparatus might be partially attributed to the in- ternal oxidative stress produced at severely high temperature.

关键词： Oryza sativa L, thermostability, chlorophyll b-less mutant, chloroplast ultrastructure, chlorophyll fluorescence, H2O2.

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