Regenerant Arabidopsis lineages display a distinct genome-wide spectrum of mutations conferring variant phenotypes

Multicellular organisms can be regenerated from totipotent differentiated somatic cell or nuclear founders [1-3]. Organisms regenerated from clonally related isogenic founders might a priori have been expected to be phenotypically invariant. However, clonal regenerant animals display variant phenotypes caused by defective epigenetic reprogramming of gene expression [2], and clonal regenerant plants exhibit poorly understood heritable phenotypic ("somaclonal") variation [4-7]. Here we show that somaclonal variation in regenerant Arabidopsis lineages is associated with genome-wide elevation in DNA sequence mutation rate. We also show that regenerant mutations comprise?a distinctive molecular spectrum of base substitutions, insertions, and deletions that probably results from decreased DNA repair fidelity. Finally, we show that while regenerant base substitutions are a likely major genetic cause of the somaclonal variation of regenerant Arabidopsis lineages, transposon movement is unlikely to contribute substantially to that variation. We conclude that the phenotypic variation of regenerant plants, unlike that of regenerant animals, is substantially due to DNA sequence mutation.     

贮藏保鲜中SO2伤害对红提葡萄香气组分的影响

采用固相微萃取技术及气相-质谱联用技术对不同SO2漂白伤害程度的红提果实进行香气成分的提取与鉴定,以探讨SO2漂白伤害对贮藏葡萄果实中香气组分的影响.结果表明,果实经漂白伤害后其具有芳香气味的气体所占比重明显下降,主要成分醇类化合物下降最多,而具有刺激难闻气味的酸类化合物所占比重明显上升;此外,4-萜烯醇、正己醇、月桂醇、松油醇、芳樟醇、橙花醇、乙酸萜烯酯及青叶醛等具有葡萄特征性香味的化合物在香气中所占比例明显下降或消失,而异辛醇、1-辛烯-3-醇、壬酸、辛酸、正癸酸、乙酸、己酸、2,6-二叔丁基对甲酚及2-丁基-5-(2-甲基丙基)-噻吩等具有臭味或刺激性气味的化合物出现或所占比重上升.说明,SO2伤害对红提果实香气的影响主要表现为香味化合物所占比重的减少或消失及异味化合物的产生.     

木糖异构酶序列结构特点、耐热机理及分子改造研究进展

近年来,随着发展低碳经济的迫切需要,可再生资源利用研究方兴未艾,其中,构建充分利用木质纤维素水解产物木糖生产乙醇的重组菌成为研究热点.木糖异构酶由于不需要辅酶,成为构建利用木糖重组酵母的首选途径.文中对近年来木糖异构酶的研究进展进行了综述.首先介绍了木糖异构酶的基本性质、序列、结构和功能特性,然后对其耐热机理进行了总结归纳;重点阐述了基于序列及结构进行的酶分子改造研究,包括底物特异性改造、热稳定性改造等;同时,结合作者的研究经历,对如何提高嗜热木糖异构酶在常温下的活性进行了探讨.最后,对木糖异构酶的研究进展进行了总结和展望,对基于结构改善木糖异构酶催化活性及构建新型高效利用木糖生产乙醇的重组菌具有重要的指导意义.     

刀鲚和凤鲚的分子鉴定及其在仔鱼种类鉴定中的应用

使用mtDNA Cyt b基因序列作为分子标记,基于400 bp左右的序列分析长颌鲚、短颌鲚及凤鲚成鱼的遗传关系。结果显示长颌鲚和短颌鲚间的遗传距离在0—0.5%之间;凤鲚与长颌鲚、短颌鲚的遗传距离分别在7.9%—8.9%和7.7%—8.6%之间。用Kimura双参数模型构建的NJ分子系统树显示,长颌鲚和短颌鲚不能形成彼此独立的分支,而是混合聚在一起形成一个分支;凤鲚则形成另一个分支。对长江口沿岸区域的鲚属仔鱼Cyt b基因片段序列分析发现,仔鱼个体之间的遗传距离为0—0.7%,仔鱼与长颌鲚、短颌鲚的遗传距离在0.1%—0.5%之间,而与凤鲚的遗传距离为8.3%—8.8%。在Kimura双参数模型构建的NJ分子系统树中,仔鱼与长颌鲚、短颌鲚聚为一类,而与凤鲚分开,表明分析的仔鱼样品不包括凤鲚个体。由于长江口一般没有短颌鲚分布,这些仔鱼应该都是长颌鲚。     

C肽与胰岛素双标记时间分辨荧光免疫分析法的建立及初步临床应用

建立钐(Sm3+)标记检测C肽(C-peptide)及铕(Eu3+)标记检测胰岛素(insulin)的双标记时间分辨荧光免疫分析法(TRFIA),并初步尝试检测人血C肽以及胰岛素含量.将抗C肽单克隆抗体(Biodesign No.E54094M)与抗insulin单克隆抗体(BiodesignNo.E86306M)混合包被96孔板,然后用Sm3+标记抗C肽单克隆抗体(Medix No.9103),Eu3+标记抗insulin单克隆抗体(Biodesign No.E86802M),运用双抗体夹心一步法建立C肽/胰岛素双标记时间分辨免疫荧光分析法.结果显示:C肽分析灵敏度为0.2μg/L,线性范围为0.5～22μg/L,平均回收率达到99.6%,分析内和分析间变异系数分别为4.6%～6.0%和5.1%～7.6%.胰岛素分析灵敏度为0.8 mU/L,线性范围为3.6～180 mU/L,平均回收率为99.4%,分析内和分析间变异系数分别为3.7%～6.0%和5.1%～8.0%.C肽/胰岛素双标记检测试剂与PerkinElmer公司对应的单标记进口试剂盒分别同时测定血清样本200份,检测结果高度相关,具有较好的一致性,相关系数分别为0.98与0.99.总之,自建C肽/胰岛素双标记时间分辨荧光免疫分析方法的性能均可以达到临床检测要求,有望替代现有国内外较为昂贵的单标记试剂,可用于胰岛素分泌不足导致的糖尿病诊断及糖尿病的大规模普查筛选.     

大豆转录因子GmNAC2a基因克隆及表达

利用NTT(核蛋白筛选系统)从大豆耐盐品种'铁丰八号'中克隆到1个新的NAC转录因子基因GmNAC2a,该基因DNA片段长度为900 bp,编码299个氨基酸,N端包含1个NAM保守域.系统进化树分析表明,GmNAC2a属于ATAF亚族,GmNAC2a与花生AhNAC1亲缘关系最近,同源性达到76.47%.GmNAC2...     

Genetically targeting new neurons in the adult hippocampus

Neurogenesis, the birth of new neu-rons from neural stem cells, is known to occur throughout life in two specific regions of the adult mammalian brain, the sub...     

Structural bases of dimerization of yeast telomere protein Cdc13 and its interaction with the catalytic subunit of DNA polymerase α

Budding yeast Cdc13-Stn1-Ten1 (CST) complex plays an essential role in telomere protection and maintenance, and has been proposed to be a telomere-specific replication protein A (RPA)-like complex. Previous genetic and structural studies revealed a close resemblance between Stn1-Ten1 and RPA32-RPA14. However, the relationship between Cdc13 and RPA70, the largest subunit of RPA, has remained unclear. Here, we report the crystal structure of the N-terminal OB (oligonucleotide/oligosaccharide binding) fold of Cdc13. Although Cdc13 has an RPA70-like domain organization, the structures of Cdc13 OB folds are significantly different from their counterparts in RPA70, suggesting that they have distinct evolutionary origins. Furthermore, our structural and biochemical analyses revealed unexpected dimerization by the N-terminal OB fold and showed that homodimerization is probably a conserved feature of all Cdc13 proteins. We also uncovered the structural basis of the interaction between the Cdc13 N-terminal OB fold and the catalytic subunit of DNA polymerase α (Pol1), and demonstrated a role for Cdc13 dimerization in Pol1 binding. Analysis of the phenotypes of mutants defective in Cdc13 dimerization and Cdc13-Pol1 interaction revealed multiple mechanisms by which dimerization regulates telomere lengths in vivo. Collectively, our findings provide novel insights into the mechanisms and evolution of Cdc13.     

一种QRS波群实时检测方法

结合模板匹配和改进的导数阈值法,提出了一种QRS波群实时检测方法CT2(combination method of template matching and improved derivative threshold)。首先,预采集一段ECG信号,使用高斯函数构造QRS模板;然后将实时采集的ECG信号使用CT2检测R波位置。为了比较算法检测精度和效率,使用CT2和基于小波模极大值的方法进行了对比。结果表明,CT2检测精度与基于小波模极大值的方法相当,但运算时间大大缩短,适于实时检测。     

生物活性肽-蛋氨酸脑啡肽对成骨细胞增殖的影响

蛋氨酸脑啡肽（Methionine Enkephalin,MENK）作为内源性物质,通过与阿片受体结合,发挥阿片样物质的生物学作用。研究表明,MENK在成熟的骨组织和成骨细胞中均有分布,并且在成骨细胞表面发现了阿片受体。实验旨在进一步研究MENK对成骨细胞增殖的影响。体外培养MC3T3-E1成骨细胞,MTT方法检测MENK对成骨细胞增殖的影响。结果表明,10-7、10-8、10-9mol/L的MENK对成骨细胞的增殖具有促进作用（P〈0.05）。提示MENK可在骨缺损疾病中发挥促进骨组织重建的作用。