Analysis and location of a rice BAC clone containing telomeric DNA sequences

BAC2, a rice BAC clone containing (TTTAGGG)_n homologous sequences, was analyzed by Southern hybridization and DNA sequencing of its subclones. It was disclosed that there were many tandem repeated satellite DNA sequences, called TA352, as well as simple tandem repeats consisting of TTTAGGG or its variant within the BAC2 insert. A 0. 8 kb (TTTAGGG)_n-containing fragment in BAC2 was mapped in the telomere regions of at least 5 pairs of rice chromosomes by using fluorescencein situ hybridization (FISH). By RFLP analysis of low copy sequences the BAC2 clone was localized in one terminal region of chromosome 6. All the results strongly suggest that the telomeric DNA sequences of rice are TTTAGGG or its variant, and the linked satellite DNA TA352 sequences belong to telomere-associated sequences.     

刈割对蜈蚣草的砷吸收和植物修复效率的影响

以野生苗移栽的蜈蚣草为试材 ,通过盆栽试验研究了收获次数对蜈蚣草生长、砷吸收和植物修复效率的影响。结果表明 :在 3次收获中 ,随着收获次数的增加 ,不同砷浓度处理之间蜈蚣草生物量的差异逐步缩小 ;不加砷的对照处理中 ,每次收获后的砷吸收速率下降趋势 ,而在 3个加砷处理中 ,第 2次收获和第 3次收获的蜈蚣草的吸砷速率为 6 3～ 75 μg/ (plant· d)、4 4～ 5 5μg/ (plant· d) ,均显著高于第 1次收获时的吸收速率。表明多次收获并没有降低砷的积累速度。由此可见 ,通过适当增加蜈蚣草的收获次数是提高砷修复效率的一种策略     

Impacts of fertilizer practices on environmental risk of nitrate in semiarid farmlands in the Loess Plateau of China

The lack of understanding of nitrate dynamics in soil profiles of semiarid regions hampers the assessment of the environmental risks associated with nitrate. A long-term field experiment established in the Loess Plateau of Northwest China in 1984 was used to investigate the seasonal dynamics of water and nitrate contents in the soil profile (0–300 cm) under bare fallow and continuous winter wheat (Triticum aestivum L.) with various fertilizer treatments. For treatments without mineral N input (i.e., no fertilizer, farmyard manure alone, and with P fertilizer), the amount of nitrate accumulated in the soil profile (52–120 kg N ha^?1, the average for June, August, February and April) was significantly lower than that (292 kg N ha^?1) accumulated in the bare fallow treatment. A large amount of nitrate (1,065 kg N ha^?1) was found accumulated in the soil profile with the treatment applied with mineral N at a rate of 120 kg N ha^?1 year^?1 for 17 years (1984–2001) and this nitrate moved downward during the wet season (from August to February). Clearly, the amount of nitrate accumulated in the soil profiles, and its tendency of downward movement, appears to potentially be an environmental risk as it may reach groundwater. Fertilization as mineral N fertilizers coupled with FYM or P resulted in 50–70% less nitrate accumulation in the soil profiles than that using mineral N fertilizer alone, and therefore the environmental risk was reduced. It is proposed that a “break point” of nitrate distribution existed in the soil profiles, providing an indication of soil depth to which nitrate can transfer.     

应用CRISPRi技术敲低耻垢分枝杆菌异柠檬酸脱氢酶基因

成簇的规律间隔的短回文重复序列干扰(clustered regularly interspaced short palindromic repeat interference,CRISPRi)是一种新型转录抑制技术,该系统包含RNA介导的DNA内切酶dCas9和针对目的基因的特异性单向导RNA(single guide RNA,sgRNA),通过形成DNA识别复合物特异性识别相应DNA序列以抑制目的基因的转录。异柠檬酸脱氢酶(isocitrate dehydrogenase,ICD)是三羧酸循环中的关键代谢酶,在分枝杆菌的碳代谢过程中发挥重要作用。本研究利用CRISPRi高效抑制分枝杆菌特定基因表达的方法构建耻垢分枝杆菌icd敲低(icd knockdown,ICD-KD)株。定量聚合酶链反应(quantitative polymerase chain reaction,qPCR)和蛋白免疫印迹检测结果显示,耻垢分枝杆菌中icd转录水平与ICD蛋白表达水平显著下降,表明采用CRISPRi技术成功构建了耻垢分枝杆菌ICD-KD株。进一步研究ICD-KD株的生长情况,测定其在固体培养基点板及液体培养基中的生长曲线,结果均显示ICD-KD株生长速率明显减慢,同时菌体内ICD酶活显著降低,提示ICD对分枝杆菌的生长存活起重要作用。本研究使用CRISPRi技术快速构建了分枝杆菌必需基因的敲低菌株,为后续研究分枝杆菌ICD在碳源代谢通路中的功能和碳通量流向调控机制提供了重要基础。     

Analysis and location of a rice BAG clone containing telomeric DNA sequences

BAC2, a rice BAC clone containing (TTTAGGG)n homologous sequences, was analyzed by Southern hybridization and DNA sequencing of its subclones. It was disclosed that there were many tandem repeated satellite DNA sequences, called TA352, as well as simple tandem repeats consisting of TTTAGGG or its variant within the BAC2 insert. A 0. 8 kb (TTTAGGG) n-containing fragment in BAC2 was mapped in the telomere regions of at least 5 pairs of rice chromosomes by using fluorescence in situ hybridization (FISH). By RFLP analysis of low copy sequences the BAC2 clone was localized in one terminal region of chromosome 6. All the results strongly suggest that the telomeric DNA sequences of rice are TTTAGGG or its variant, and the linked satellite DNA TA352 sequences belong to telomere-associated sequences.     

Analysis and location of a rice BAG clone containing telomeric DNA sequences

BAC2, a rice BAC clone containing (TTTAGGG)_n homologous sequences, was analyzed by Southern hybridization and DNA sequencing of its subclones. It was disclosed that there were many tandem repeated satellite DNA sequences, called TA352, as well as simple tandem repeats consisting of TTTAGGG or its variant within the BAC2 insert. A 0. 8 kb (TTTAGGG)_n-containing fragment in BAC2 was mapped in the telomere regions of at least 5 pairs of rice chromosomes by using fluorescencein situ hybridization (FISH). By RFLP analysis of low copy sequences the BAC2 clone was localized in one terminal region of chromosome 6. All the results strongly suggest that the telomeric DNA sequences of rice are TTTAGGG or its variant, and the linked satellite DNA TA352 sequences belong to telomere-associated sequences.     

超富集植物吸收富集重金属的生理和分子生物学机制

与普通植物相比,超富集植物在地上部富集大量重金属离子的情况下可以正常生长,其富集重金属的机理已经成为当前植物逆境生理研究的热点领域．尤其是近两年,随着分子生物学等现代技术手段的引人,关于重金属离子富集机理的研究取得了一定进展．通过与酵母突变株功能互补克隆到了多条编码微量元素转运蛋白的全长cDNA;也从分子水平上研究了谷胱甘肽、植物螯合素、金属硫蛋白、有机酸或氨基酸等含巯基物质与重金属富集之间的可能关系．本文从植物生理和分子生物学角度简要评述超富集植物对重金属元素的吸收、富集、整合及区室化的机制．     

黑斑蛙早期胚胎发育过程中乳酸脱氨酶同工酶的初步研究

本文采用聚丙烯酰胺凝胶电泳方法,对河南新乡地区黑班蛙（Rananigromaculata）早期胚胎发育过程中（受精后0－324h）乳酸脱氢酶（LDH）同工酶进行了研究。结果表明：LDH1自始至终存在,且活性一直占绝对优势;LDH5比于心跳期出现,该期以后其活性仅次于LDH1;LDH2于襄胚早期开始出现,其活性一直较弱;LDH3和LDH4均于开口期少量出现,以后前者活性一直极弱,后者则呈现一定的活性。与哺乳类及鱼类资料比较,提示两栖类黑斑蛙LDH同工酶有其独特的表达谱式。