奠基者效应对海南坡鹿迁地保护种群遗传多样性的影响

在迁地保护中,奠基者效应通常会导致新建种群与源种群的遗传分化,并使新建种群的遗传多样性低于源种群。海南坡鹿(Cervuseldi hainanus)是世界濒危种,野生种群仅分布在中国海南岛。由于栖息地破坏和过度狩猎,至20世纪70年代,这个物种仅剩26只,已经濒临绝灭,被列为国家一级保护动物。自1976年开始对海南坡鹿实施就地保护和迁地保护,该种群的数量从最初的26只增加到1600多只。本文采用10个微卫星位点对一个源种群(大田种群)和5个迁地种群(邦溪、甘什岭、枫木、金牛岭、文昌种群)的遗传多样性进行检测,结果发现6个种群的遗传多样性水平均较低(He≈0·3);5个迁地种群分别有1、3或5个单态位点,大田种群无单态位点;邦溪种群与大田种群遗传分化显著,而甘什岭种群与大田种群的遗传分化不显著。结果表明,奠基者效应导致种群的遗传多样性水平较低,并且对于不同迁地种群,影响也不相同。造成这些差异的因素有建群者数量、引种方式和建群种群的结构。该研究为今后在海南岛建立新的海南坡鹿迁地种群提供建议和参考,同时也为其他濒危物种的迁地保护提供理论指导。     

病毒侵染对西伯利亚百合DNA甲基化的影响

采用基于AFLP的甲基化敏感扩增多态性(MSAP)技术,用10对引物对侵染百合花叶病毒和丛簇病毒的西伯利亚百合植株和无毒植株进行DNA甲基化水平和模式分析.结果发现,西伯利亚百合无毒植株和病毒侵染植株的平均甲基化水平分别为40.1%和31.5%;平均全甲基化率分别为13.0%和9.7%;半甲基化率分别为27.1%和21.8%.研究表明,百合DNA甲基化多以半甲基化的形式存在;病毒侵染导致百合植株DNA甲基化水平降低,且对整体甲基化水平、全甲基化水平和半甲基化水平均产生了影响;说明病毒侵染百合后植株出现的症状在一定程度上与DNA甲基化存在关联.     

C. elegans MCM-4 is a general DNA replication and checkpoint component with an epidermis-specific requirement for growth and viability

DNA replication and its connection to M phase restraint are studied extensively at the level of single cells but rarely in the context of a developing animal. C. elegans lin-6 mutants lack DNA synthesis in postembryonic somatic cell lineages, while entry into mitosis continues. These mutants grow slowly and either die during larval development or develop into sterile adults. We found that lin-6 corresponds to mcm-4 and encodes an evolutionarily conserved component of the MCM2-7 pre-RC and replicative helicase complex. The MCM-4 protein is expressed in all dividing cells during embryonic and postembryonic development and associates with chromatin in late anaphase. Induction of cell cycle entry and differentiation continues in developing mcm-4 larvae, even in cells that went through abortive division. In contrast to somatic cells in mcm-4 mutants, the gonad continues DNA replication and cell division until late larval development. Expression of MCM-4 in the epidermis (also known as hypodermis) is sufficient to rescue the growth retardation and lethality of mcm-4 mutants. While the somatic gonad and germline show substantial ability to cope with lack of zygotic mcm-4 function, mcm-4 is specifically required in the epidermis for growth and survival of the whole organism. Thus, C. elegans mcm-4 has conserved functions in DNA replication and replication checkpoint control but also shows unexpected tissue-specific requirements.     

约氏疟原虫Pys48核酸疫苗传播阻断效应的实验研究

探讨约氏疟原虫（Plasmodium yoelii17XL）Pys48核酸疫苗免疫BALB/c小鼠的特异性抗体产生特点及其效应。将Pys48核酸疫苗肌肉内注射免疫BALB/c小鼠,并以空质粒注射组作为对照,3次免疫后通过P.y17XL攻击小鼠;采用ELISA检测免疫后小鼠血清中特异性抗体水平;通过P.y17XL感染小鼠,取其感染后第3天含有配子体的血液进行体外培养,观察合子、动合子的形成数量。ELISA结果显示疫苗免疫组小鼠血清特异性抗体滴度明显高于对照组;而合子、动合子数量明显低于对照组。提示Pys48核酸疫苗具有良好的免疫原性,免疫小鼠后可以建立起有效的传播阻断效应。     

MRN复合物的结构及功能研究进展

MRN复合物包括MRE11、NBS1、RAD50,此复合物中的MRE11或NBS1缺失或突变会导致人的共济失调一毛细血管扩张样疾病、Nijmegen断裂综合征。MRN复合物在DNA双链损伤修复、同源重组、非同源重组、端粒长度维持、细胞检验点激活、保证DNA复制的顺利进行,以及维持基因组的稳定性等方面都起到了重要的作用。从以上几个方面简要综述MRN复合物的研究进展。     

椭圆食粉螨线粒体DNA CO Ⅰ基因片段序列分析

采用苯酚-氯仿-异戊醇抽提法提取了采自江西南昌和广州潮州2个地理种群的椭圆食粉螨Aleuro-glyphus ovatus Troupeau,1878基因组DNA。以相应引物对椭圆食粉螨线粒体DNA细胞色素氧化酶I亚基基因(mtDNA COI)进行PCR扩增,直接测序,得到379bp的碱基片断(国际基因库索引号EF527825),其碱基序列A、C、G、T含量分别为71bp(18.73%)、53bp(13.98%)、89bp(23.48%)、166bp(43.80%);江西南昌和广州潮州2个地理种群间的椭圆食粉螨mtDNACOI基因片段完全一致,未发现地理差异。     

Critical nuclear DNA size and distribution associated with S phase initiation

Using HeLa S-3 cells synchronized by selective detachment, in this paper we report a parallel study of nuclear morphology and autoradiography grain patterns between middle G₁ and middle S phases: Our results show two distinct [³H]-thymidine labeling patterns. The first “peripheral” labeling pattern has a characteristic nuclear size distribution, in contrast to the heterogeneous and varying size distributions of Feulgen-stained nuclei, and apparently is characteristic of very early S phase. The sizes of the second labeling pattern—homogeneous or inhomogeneous grain distribution throughout the nucleus—are equal or larger than the first and vary with S phase progression. Together, the corresponding nuclear sizes of the labeled nuclei represent the larger extreme of nuclear areas, and the labeling index closely parallels the fraction of nuclei with areas larger than the minimum size of the labeled nuclei. These results suggest a characteristic nuclear size (reflecting unique intranuclear DNA distribution) as a necessary, if not sufficient, requirement for S phase initiation. Parallel experimentation with rat liver cells—synchronized in vivo by partial hepatectomy and analyzed by thin section autoradiography—confirms the existence of a peripheral labeling pattern in both the very early part and the very late part of S phase, which reconciles our data with previous results and points to the fact that both initiation and termination sites for DNA replication are near the nuclear periphery.     

Methods of DNA extraction and PCR amplification for individual freshwater mussel (Bivalvia: Unionidae) glochidia,with the first report of multiple paternity in these organisms

Freshwater mussels (Unionidae) are among North America's most imperilled organisms. Mussels produce small larvae (glochidia) that parasitize aquatic vertebrates. We modified the Epicentre QuickExtract protocol to extract DNA from a single glochidium, collected directly from the marsupium of a female mussel, to use as template in polymerase chain reactions (PCRs). Yield per glochidium in a 40 µL extraction volume provided enough DNA for ≥ 15 PCRs per individual. We were successful in using this DNA for microsatellite analysis of up to three loci per individual. Offspring from one female showed evidence for multiple paternity within her brood. Our results are the first documentation of this phenomenon in freshwater mussels.