甘蔗花叶病和宿根矮化病多重PCR检测方法的建立

 【目的】建立能同时检测甘蔗花叶病（sugarcane mosaic virus,SCMV）和宿根矮化病（ratoon stunting disease,RSD）的多重PCR检测方法。【方法】以病株带鞘叶组织总核酸反转录物为模板,根据中国甘蔗花叶病的主要致病病原高梁花叶病毒SrMV和甘蔗花叶病毒中国大陆优势株系SCMV-A,结合B、D、E和SC株系的外壳蛋白核苷酸序列的保守区设计PCR引物对和已有的检测甘蔗宿根矮化病病原木质部赖氏杆菌木质部亚种（Leifsonia xyli subsp. Xyli,Lxx）的PCR引物对,在SCMV RT-PCR和RSD单一PCR体系的基础上,建立并优化可同时检测SCMV和RSD的多重PCR检测方法。【结果】此检测方法可特异地从感染SCMV和RSD的样品中扩增出SCMV（400 bp）和RSD（265 bp）2个条带,扩增产物测序结果表明,SCMV扩增产物与GenBank中其它株系或分离物的核苷酸序列同源性为81%～99%,RSD扩增产物与GenBank中其它株系或分离物的核苷酸序列同源性为91%～99%。【结论】应用此检测方法可稳定、特异地检测出蔗株中是否有导致甘蔗花叶病和宿根矮化病的单一或混合的病原。     

广西蔗区甘蔗花叶病病毒种群分析

[目的]明确引起广西蔗区甘蔗花叶病的病原,为甘蔗抗花叶病育种、种质筛选及病害防控提供科学依据.[方法]从广西主要蔗区采集不同品种显症或不显症甘蔗叶片,提取RNA后采用甘蔗花叶病毒(SCMV)、高粱花叶病毒(SrMV)、玉米矮化病毒(MDMV)和约翰逊草花叶病毒(JGMV)特异引物进行一步法RT-PCR检测,将目的片段克隆并测序;病毒CP基因序列在GenBank数据库中进行比对分析.[结果]在收集的48份样品中检测出SrMV阳性33份,SCMV阳性2份,SCMV和SrMV复合侵染1份,未检测到MDMV和JGMV.花叶病的发病率为75.0％,其中,SrMV、SCMV及两种病毒复合侵染的发病率分别为68.8％、4.2％和2.1％.台糖系列及其他引进品种的甘蔗花叶病感病率较高,桂糖系列品种的感病率相对较低.[结论]甘蔗花叶病已在广西大部分蔗区发生,其致病原以SrMV为主,SCMV零星发生,由SCMV和SrMV复合侵染的甘蔗花叶病发生机率较低.广西蔗区可能存在其他种类病原病毒引起的甘蔗花叶病.     

甘蔗宿根矮化病菌PCR检测及目的片段核苷酸序列分析

根据甘蔗宿根矮化病(RatoonStuntingDisease,RSD)病原细菌(Leifsoniaxylisubsp.xyli,Lxx)16S-23SrDNA基因间隔区核苷酸序列设计的一对特异性引物,建立了甘蔗宿根矮化病PCR检测方法;同时对PCR扩增的目的片段核苷酸序列进行测定与分析。结果表明广东湛江蔗区RSD病菌16S-23SrDNA基因间隔区核苷酸序列与巴西、澳大利亚及美国路易斯安娜州RSD株系基因组相应区段核苷酸同一率接近100%,病菌高度的同源。而与近缘的木质部赖氏杆菌狗牙根变种(Leifsoniaxylisubsp.Cynodontis,Lxc)和形态上相近的马铃薯环腐病菌(Clavibactermichiganensissubsp.Michiganensis)基因组相应区段核苷酸同一率较低,存在明显的分化。     

甘蔗杂交种子传播甘蔗花叶病毒、高粱花叶病及黄叶病的检测

[目的]探究甘蔗杂交种子对甘蔗花叶病毒、高粱花叶病及黄叶病的传播性,为甘蔗抗病育种提供参考.[方法]采集父本或母本感染花叶病或黄叶病的甘蔗杂交种子样品10份,分别以SCMV、SrMV和SCYLV特异性引物进行一步法RT-PCR扩增、克隆和测序分析.对田间实生苗进行生物学观察,并采用RT-PCR检测其叶片SCMV、SrMV和SCYLV携带性.[结果]经特异性引物检测,10份杂交种子中仅有样品H4显示SrMV阳性,扩增的特异片段大小为828 bp,其核苷酸序列与GenBank中已报道的SrMV基因序列同源性达99％.聚类分析结果表明,样品H4的SrMV和GenBank中SrMV外壳蛋白序列的自举水平达100％,证实H4样本感染的病毒为SrMV.田间连续45 d观察均未发现出现病毒症的甘蔗幼苗;经RT-PCR检测,均未在10个样品实生苗叶片中发现此3种病毒.[结论]甘蔗种子可携带高粱花叶病(SrMV),但未能通过种子传播至实生苗.     

甘蔗花叶病毒南城分离物外壳蛋白基因序列测定及分析

从江西南城甘蔗病株中获得1个甘蔗花叶病毒(Sugarcane mosaic virus,SCMV)分离物,命名为SCMV-NCH。根据SCMV外壳蛋白(CP)基因N-端和C-端保守序列设计引物,对SCMV-NCH的CP基因进行RT-PCR扩增、克隆和测序,获得924个核苷酸(nt),推断编码308个氨基酸(aa)的近全长CP基因序列。与SCMV亚组SCMV、高粱花叶病毒(SrMV)、玉米矮花叶病毒(MDMV)、约翰逊草花叶病毒(JGMV)、玉米花叶病毒(ZeMV)、白草花叶病毒(PenMV)等6种病毒代表性株系外壳蛋白氨基酸序列同源性比较结果显示,SCMV-NCH与SCMV的同源性最高(86.2%),与其他5种病毒同源性相对较低(56.4%~72.2%)。与SCMV13个分离物外壳蛋白氨基酸序列进行同源性比较并构建关系树,结果显示SCMV-NCH与我国浙江2个分离物(Yuhang和Xiaosh)具有最近的亲缘发生关系。     

江苏玉米矮花叶病病原鉴定

可以感染玉米引起花叶症状的病毒有玉米矮花叶病毒(MDMV)、甘蔗花叶病毒(SCMV)、约翰逊草花叶病毒(JGMV)和高粱花叶病毒(SrMV)等4种,目前国内主要认为是SCMV.为明确江苏发生的玉米矮花叶病的病原,2011年从姜堰田间采集自然发生的呈现玉米矮花叶病典型症状的玉米病叶,初提纯物电镜观察可见750 nm×13 nm线状病毒粒子.根据已经发布的SCMV设计特异性引物,通过RT-PCR扩增获得预期的CP、HC-Pro、NIb和Vpg基因片段,而用MDMV、JGMV和SrMV特异性引物未扩增到预期目的片段.序列测定和同源性分析表明,扩增到的基因片段序列与SCMV对应基因片段序列的同源性在90％以上,与SCMV亚组中另外3个株系MDMV、SrMV和JGMV相应基因片段序列的同源性在80％以下.由此判断姜堰玉米矮花叶病的病原为SCMV.     

甘蔗花叶病毒复制酶基因的克隆及序列分析

以甘蔗花叶病毒(SCMV)福建分离物(FJ)的总RNA为模板,用RT-PCR方法扩增了含有复制酶(NIb)基因的DNA片段,将其克隆到质粒pGM-T载体上并进行了序列分析。结果表明,NIb基因由1563个碱基组成,编码521个氨基酸并含有高度保守序列GDD。NIa/NIb和NIb/CP交界处的蛋白酶切割位点分别为Q/C和Q/A。与国外报道的SCMV亚组几个株系分离物相比,NIb基因(福建分离物)的核苷酸和氨基酸序列同源性分别为57.8%~86.9%和60.9%~95.2%,其中与SCMV-SA株系的核苷酸及氨基酸序列同源性则高达86.9%和95.2%。     

高粱红条病病原的分子鉴定

从山西高粱红条病病叶中得到一种病毒分离物,命名为GL-SX.根据甘蔗花叶病毒亚组(SCMV subgroup)外壳蛋白(CP)基因C-端和复制酶(NIb)基因C-端的保守序列设计引物,对GL-SX进行免疫捕获反转录PCR (IC-RT-PCR) 扩增,获得一条长约1.1 kb的扩增片段,扩增片段克隆后测定序列,该序列含1087个核苷酸(nt),编码362氨基酸(aa),取其中的近全长CP氨基酸序列(296 aa)与甘蔗花叶病毒(Sugarcane mosaic virus, SCMV)、玉米矮花叶病毒 (Maize dwarf mosaic virus, MDMV)、高粱花叶病毒(Sorghum mosaic virus, SrMV)和约翰逊草花叶病毒(Johnsongrass mosaic virus, JGMV) 等4种病毒的对应序列进行同源性比较,结果与SCMV的同源性最高(95.3%),而与SrMV、MDMV和JGMV等3种病毒的同源性相对较低,依次为69.3%、69.1%和55.4%.根据Potyvirus属病毒种类划分的标准,将GL-SX鉴定为SCMV.将GL-SX的近全长CP氨基酸序列与SCMV种内各分离物的对应序列进行同源性比较及构建关系树,结果显示GL-SX与SCMV-MDB具有较远缘的种内亲缘关系,而与德国的一个SCMV玉米分离物(SCVM-Hoe)及中国的两个玉米分离物(SCMV-ZJ和SCMV-BJ)具有很高的同源性.     

甘蔗脱毒健康种苗宿根矮化病的PCR检测

[目的]为甘蔗脱毒健康种苗宿根矮化病的检测提供好的方法。[方法]利用PCR技术对甘蔗脱毒健康种苗进行甘蔗宿根矮化病（RSD）病菌的检测研究。[结果]在甘蔗健康种苗生长的前几个不同时期（组培苗增殖、生根、丛苗沙培和单株假植阶段）,甘蔗宿根矮化病菌的检测结果均为阴性。对PCR检测灵敏度的研究表明,PCR能够检测到甘蔗宿根矮化病菌液浓度10-3。[结论]PCR检测特异性好、灵敏度高,适合甘蔗脱毒健康种苗生产中的大批量检测。     

Hotspots, basalts, and the evolution of the mantle

The trace element concentration patterns of continental and ocean island basalts and of mid-ocean ridge basalts are complementary. The relative sizes of the source regions for these fundamentally different basalt types can be estimated from the trace element enrichment-depletion patterns. Their combined volume occupies most of the mantle above the 670 kilometer discontinuity. The source regions separated as a result of early mantle differentiation and crystal fractionation from the resulting melt. The mid-ocean ridge basalts source evolved from an eclogite cumulate that lost its late-stage enriched fluids at various times to the shallower mantle and continental crust. The mid-ocean ridge basalts source is rich in garnet and clinopyroxene, whereas the continental and ocean island basalt source is a garnet peridotite that has experienced secondary enrichment. These relationships are consistent with the evolution of a terrestrial magma ocean.     

Climate change, deforestation, and the fate of the Amazon

The forest biome of Amazonia is one of Earth's greatest biological treasures and a major component of the Earth system. This century, it faces the dual threats of deforestation and stress from climate change. Here, we summarize some of the latest findings and thinking on these threats, explore the consequences for the forest ecosystem and its human residents, and outline options for the future of Amazonia. We also discuss the implications of new proposals to finance preservation of Amazonian forests.     

Diamonds, Eclogites, and the Oxidation State of the Earth's Mantle

The reaction dolomite + 2 coesite --><-- diopside + 2 diamond + 2O(2) defines the coexistence of diamond and carbonate in mantle eclogites. The oxygen fugacity of this reaction is approximately 1 log unit higher at a given temperature and pressure than the oxygen fugacities of the analogous reactions that govern the stability of diamond in peridotite. This difference allows diamond-bearing eclogite to coexist with peridotite containing carbonate or carbonate + diamond. This potential coexistence of diamond-bearing eclogite and carbonate-bearing peridotite can explain the presence of carbon-free peridotite interlayered with garnet pyroxenites that contain graphitized diamond in the Moroccan Beni Bousera massif at the Earth's surface and the preferential preservation of diamond-bearing eclogitic relative to peridotitic xenoliths in the Roberts Victor kimberlite.     

Pre-Columbian urbanism, anthropogenic landscapes, and the future of the Amazon

The archaeology of pre-Columbian polities in the Amazon River basin forces a reconsideration of early urbanism and long-term change in tropical forest landscapes. We describe settlement and land-use patterns of complex societies on the eve of European contact (after 1492) in the Upper Xingu region of the Brazilian Amazon. These societies were organized in articulated clusters, representing small independent polities, within a regional peer polity. These patterns constitute a "galactic" form of prehistoric urbanism, sharing features with small-scale urban polities in other areas. Understanding long-term change in coupled human-environment systems relating to these societies has implications for conservation and sustainable development, notably to control ecological degradation and maintain regional biodiversity.     

Oxytocin, vasopressin, and the neurogenetics of sociality

There is growing evidence that the neuropeptides oxytocin and vasopressin modulate complex social behavior and social cognition. These ancient neuropeptides display a marked conservation in gene structure and expression, yet diversity in the genetic regulation of their receptors seems to underlie natural variation in social behavior, both between and within species. Human studies are beginning to explore the roles of these neuropeptides in social cognition and behavior and suggest that variation in the genes encoding their receptors may contribute to variation in human social behavior by altering brain function. Understanding the neurobiology and neurogenetics of social cognition and behavior has important implications, both clinically and for society.