人参植物皂苷生物合成相关新基因的筛选与鉴定

人参植物根进行的特定发育过程在药用次生物———人参皂苷生物合成和累积中发挥重要作用。为从人参根中分离出人参皂苷生物合成相关基因 ,采用抑制差减杂交技术 ,构建四年和一年生人参根组织mRNA群体间正向差减cDNA文库。对从差减文库中筛选的 4 0个阳性cDNA克隆进行酶切、PCR与逆向Northern斑点杂交鉴定、DNA测序以及核苷酸序列同源性比较。结果表明 ,获得的 6个差减克隆在GenBank/DDBJ/BMBL无对应的同源基因 ,代表新基因序列。与此同时 ,使用Northern印迹杂交验证及半定量RT PCR进一步确认 ,6个转录本为根发育阶段差异性表达基因。因而提示 ,它们可能在人参皂苷生物合成中发挥了重要作用。此外 ,在人参茎、叶与种子中亦能检测到上述基因转录本的表达。目前 ,6个新基因已被命名 ,在GenBank注册并获登录号 ,为克隆上述新基因cDNA全长序列及深入鉴定其在人参皂苷生物合成中的功能提供了重要实验依据。     

抑制差减杂交法分离玉米幼苗淹水诱导表达基因

以淹水处理(submergence-treated, ST)的玉米(Zea mays L.)幼苗根部cDNA为目标群体,未处理(untreated, UT)的玉米幼苗根部cDNA为对照群体,进行抑制差减杂交.用经过UT差减的ST cDNA构建了一个含有大约2 000个独立克隆的差减文库.对随机挑取的408个克隆进行差异筛选,获得了184个在ST中特异表达或表达增强的候选克隆.对其中155个cDNA克隆测序并去除重复克隆后,共得到95个差异表达的cDNA片段.GenBank中BLAST查询结果表明:6个克隆为已知的玉米核苷酸序列;68个克隆与已知基因或EST序列部分区域的同源性为60%～90%;21个克隆在GenBank中无法查到对应的同源序列,可能代表了新基因,或者由于序列位于变异丰富的3′端而无法查到与其他物种基因的同源性.     

人参皂苷生物合成相关新基因GBR6的cDNA克隆及序列分析

从人参根组织中分离总RNA,使用RT—PCR扩增出人参皂苷生物合成相关基因GBR6开放阅读框(ORF)cDNA片断,并将其定向克隆入原核高效表达载体pQE30,阳性克隆经BamHⅠ和PstⅠ双酶切鉴定、测序验证与已知的GBR6ORF序列完全一致．因而成功构建了pQE30-GBR60RF融合原核表达载体,为下一步进行GBR6功能表达分析奠定了基础．     

抑制差减杂交法分离玉米幼苗淹水诱导表达基因

以淹水处理（submergence-treated,ST)的玉米（Zea maysL.)幼苗根部cDNA为目标群体,未处理（untreated,UT)的玉米幼苗cDNA为对照群体,进行抑制差减杂交。用经过UT差减的STcDNA构建了一个含有大约2000个独立克隆的差减文库。对随机挑取的408个克隆进行差异筛选。获得了184个在ST中特异表达或表达增强的候选克隆。对其中155个cDNA克隆测序并去除重复克隆后,共得到95个差异表达的cDNA片段。GenBank中BLAST查询结果表明;6个克隆为已知的玉米核苷酸序列;68个克隆与已知基因或EST序列部分区域的同源性为60%-90%;21个克隆在GenBank中无法查到对应的同源序列。可能代表了新基因。或者由于序列位于变异丰富的3′端而无法查到与其他物种基因的同源性。     

文昌鱼性腺差减cDNA文库的构建

本研究以日本文昌鱼(Branchiostoma japonicum)性腺cDNA为材料,应用抑制性差减杂交技术构建文昌鱼雌雄性腺的差减cDNA文库.正向差减杂交以卵巢为试验方、精巢为驱动方,反向差减杂交以精巢为试验方、卵巢为驱动方,将所获差减cDNA片段克隆插入质粒表达载体,转化大肠杆菌DH5α,最后获得的正、反向差减文库分别含459、243个重组子.PCR 扩增鉴定正、反向差减cDNA文库的插入片段,其中90%左右的克隆皆能扩增出有效产物,插入片段范围为200-600 bp,符合差减文库PCR产物片段的大小.随机选取30个阳性克隆测序分析,得到26有效基因片段,进一步从中选取16个序列,用实时定量PCR对文库质量进行验证,结果表明所建文库能够达到富集雌雄性腺差异表达基因的目的.文昌鱼性腺差减文库的构建,为进一步分离、鉴定性腺分化和发育相关基因奠定了基础[动物学报 54(3):482-48 8,2008].     

无核荔枝果实形成差异表达基因cDNA的克隆

采用抑制差减杂交技术(Suppression Subtractive Hybridization,SSH)分离与海南无核荔枝果实形成相关的差异表达基因的cDNA片段,为克隆相关基因提供研究基础。分别以无核荔枝的有核幼果为driver;无核幼果为tester,建立差减cDNA文库。经Reverse Northern Dot-Blot筛选该文库,共获得61个阳性克隆,随机选取17个克隆进行测序,共获得10条非重复序列,对其中较长的7个序列进行同源分析,结果表明:有6个序列在荔枝中为首次报道。     

用抑制差减杂交法分离和克隆梭梭幼苗受渗透胁迫诱导相关基因的cDNA片段

以Hoagland溶液培养的梭梭幼苗(H)为对照群体,甘露醇处理的梭梭幼苗(M)为目标群体,进行抑制差减杂交.用经过H cDNA差减的M cDNA构建了一个含有大约400个独立克隆的差减文库;采用差减前的H cDNA和M cDNA以及正向/反向差减杂交后的cDNA为模板标记探针,对随机挑取的100个重组质粒进行差示筛选,获得了21个阳性候选克隆.从这些阳性候选克隆中随机挑取了8个进行Northern blot分析,证实其中3个候选克隆代表了在M中特异表达或表达增强的基因,序列分析和同源性比较表明它们与逆境胁迫有关;而另外5个候选克隆无Northem杂交信号,推测它们为低丰度转录本.     

大鼠再生肝中表达上调基因的筛选与鉴定

采用新发展的抑制差减杂交技术（suppression subtractive hybridization,SSH）在基因组水平筛选再生肝中高表达基因。大鼠肝部分切除后24h的再生杆组织来源的cDNA作为受检者（tester）,正常肝组织的cDNA作为驱动者（driver）,进行差减杂交,获得一900个克隆的差减杂交库,随后对差减克隆进行了差异筛选,得到50个在再生肝中高表达的强阳性克隆,序列测定和同源比较表明这些克隆代表了37个基因,其中13个与已报道的肝再生相关的基因同源,15个为忆知基因但首次发现与肝再生相关,9个为新的基因（EST）已被GenBank收录。制备了标准化RNA点杂交膜,通过对上述部分基因的RNA点杂交分析,不但确认了这些基因在再生肝中表达水平的升高,同时发现它们在肝再生过程中有不同的表达模式。实验结果提示这些基因在肝再生过程中具有重要功能。     

用抑制差减杂交法分离和克隆梭梭幼苗受渗透胁迫诱导相关基因的cDNA片段

以Hoagland溶液培养的梭梭幼苗（H）为对照群体,甘露醇处理的梭梭幼苗（M）为目标群体,进行抑制差减杂交。用经过H cDNA差减的M cDNA构建了一个含有大约400个独立克隆的差减文库;采用差减前的H cDNA和M cDNA以及正向／反向差减杂交后的cDNA为模板标记探针,对随机挑取的100个重组质粒进行差示筛选,获得了21个阳性侯克隆,从这些阳性候选克隆中随机挑取了8个进行Northern blot分析。证实其中3个候选克隆代表了在M中特异表达或表达增强的基因,序列分析和同源性比较表明它们与逆境胁迫有关;而另外5个候选克隆无Northern杂交信号,推测它们为低丰度转录本。     

用表达性差异显示分析技术分离人胎肝组织选择性表达基因

目的：建立4月龄人胎肝组织选择性表达基因EST库,为研究胚胎肝组织特异表达基因提供有力的工具。方法：采用表达性差异显示分析（representational difference analysis,RDA) 技术建立4月龄人胎肝组织选择性表达基因EST库,并测定部分克隆核苷酸序列,以竞争PCR检测代表性基因的差异表达。结果与结论：以珠蛋白家族基因为标志,所建差减cDNA文库中α－珠蛋白家族基因的表达频率较未差减cDNA文库增高7倍,同时该文库也含有多种与肝生长密切相关的基因,表明RDA技术确是研究差异表达基因的有效手段,所建EST库富集胎肝特异表达基因。部分克隆序列分析获得2种未报道序列,其中一株含有丝／苏氨酸激酶结构域,表明可望从此库中分离具有重要未知功能的新基因。     

Selective enrichment of cDNAs from salt-stress-induced genes in the wheatgrass, Lophopyrum elongatum, by the formamide-phenol emulsion reassociation technique

We present a novel technique for the enrichment of cDNA libraries to enhance the abundance of clones of differentially expressed genes. The technique is relatively simple, requires moderate quantities of poly(A) + RNA and results in preferential enrichment of clones derived from mRNAs that were of low abundance in their original population. This method was used to isolate cDNA clones of salt-stress-induced genes in the roots of Lophopyrum elongatum, a highly salt-tolerant wheatgrass. An excess of sonicated plasmid DNA from a cDNA library from nonstressed roots was hybridized in a formamide-phenol emulsion with inserts from a cDNA library of stressed roots. Clones that were more abundant in, or were unique to, the library of the stressed roots were recovered as double-stranded fragments by virtue of reconstituted restriction-enzyme-digested ends by ligating them to a plasmid vector. The resulting enriched library was screened by differential colony hybridization and clones of eleven different genes that were more strongly expressed in stressed roots than in controls were selected.     

Screening and comparison of differentially expressed genes between one MDR-TB strain and the virulent M. tuberculosis H37Rv

To screen and compare the differentially expressed genes between one MDR-TB strain separated from one child patient and the virulent Mycobacterium tuberculosis H37Rv, suppression subtractive hybridization (SSH) technology was used to build a library of cDNAs that were differentially expressed in the MDR and H37Rv. From this cDNA library, genes that were expressed in the MDR-TB but not in the H37Rv were selected for gene sequencing and homology analysis; 113 positive clones were obtained, their cDNA fragments were sequenced, and homology analysis was performed. Four novel sequences were identified. The results provide a partial list of genes differentially expressed in MDR-TB and four novel genes were found. Identification of these genes may contribute to our understanding of MDR-TB development.     

应用抑制性消减杂交技术筛选流感病毒感染宿主应答基因

从宿主系统寻找病毒感染特异性相关的生物大分子是研究病毒药物靶标和诊断标志物的新方向 .为了筛选宿主细胞中流感病毒感染特异性基因 ,采用抑制性消减杂交技术 (SSH) ,以流感病毒A 鲁防 93 9(H3N2 )感染MDCK细胞及正常MDCK细胞为材料 ,构建病毒感染特异性差减cDNA文库 ,PCR法扩增鉴定其中插入片段大小 .从差减文库中随机挑取 10 0个克隆进行测序 ,用生物信息学方法对其同源性和基因功能进行分析和预测 .结果显示 ,成功构建了流感病毒感染特异性差减cDNA文库 ,文库中cDNA片段长度在 2 5 0～ 10 0 0bp之间 .从文库中随机选取 10 0个克隆测序 ,获得了 95个有效序列 ,经blast同源性分析发现 ,大部分基因为参与宿主细胞能量代谢和蛋白质生物合成过程中的基因 ;其中 19个为无任何功能线索的新基因片段 .流感病毒感染特异性差减cDNA文库的建立和筛选出病毒感染应答候选新基因cDNA片段 ,为发现新型流感病毒药靶和诊断标志物以及病毒感染机制研究打下基础     

糙皮侧耳原基期差异表达基因分析

为解析糙皮侧耳原基期与菌丝期差异表达的基因,本研究以原基期cDNA为检测子（tester）、双核菌丝期cDNA为驱赶子（driver）,采用抑制性消减杂交法（suppression subtractive hybridization,SSH）构建了糙皮侧耳SSH cDNA文库。菌液PCR验证SSH cDNA文库插入cDNA片段后,挑取了2 055个差异转化子,差异转化子经3次反向Northern杂交筛选,得423个信号差异显著的克隆;阳性克隆测序后,经NCBI数据库Blastn和Blastx比对,共得206条差异表达序列（expressed sequence tag,EST）,重复序列去除后,有46个基因参与了细胞急救和防御、能量代谢、转录和蛋白调控、膜蛋白和信号转导,18个基因编码未知功能的推定蛋白,5个无任何同源性的新基因。挑取10个差异表达基因进行半定量RT-PCR,发现这些序列在原基期的表达水平显著高于菌丝期。结果表明,本研究成功构建了糙皮侧耳原基期与菌丝期SSH cDNA文库,为进一步分离糙皮侧耳生长发育相关基因并研究糙皮侧耳的发育机制奠定了基础。     

Isolation and Identification of Submergence-induced Genes in Maize Seedlings by Suppression Subtractive Hybridization

To investigate the expression profile of maize genes induced by submergence, a subtracted cDNA library of maize seedling roots was constructed using suppression subtractive hybridization (SSH). The cDNA of maize seedling roots treated with submergence (ST) was used as tester and what from untreated roots (UT) as driver. Products of the secondary PCR from the forward subtraction were cloned into T/A vector and transferred into Escherichia coli strain JM10B by electroporation. Four hundred and eight randomly chosen transformants carrying cDNA fragments were screened with PCR-Select Deferential Screening Kit. One hundred and eighty-four cDNA clones were identified as submergence specifically induced or highly expressed. After sequencing and removing redundant cDNAs, we got 95 submergence-induced cDNA clones. Of the 95 cDNA clones, 68 contain the regions with 60%-90% identity to their homolog in GenBank, 21 are expected to be novel genes, only 6 correspond to the published maize sequences. Key words: maize; expression profile; suppression subtractive hybridization (SSH); submergence     

Systematic isolation of genes expressed at low levels in inflorescence apices of Arabidopsis thaliana.

We constructed an equalized cDNA library from Arabidopsis inflorescence shoot apices including inflorescence meristem, floral meristem and flower tissue collected before stage 5 of flower development. The cDNA clones were arrayed on membranes and were differentially screened using cDNA pools from vegetative and inflorescence tissues as probes. Each clone was classified by expression specificity and expression level. By removing the clones that displayed hybridization signals, 384 out of 3264 clones in this library remained as candidates for inflorescence-specific mRNAs expressed at low levels. Sequence analysis of all selected clones indicated that 53 were identical and 120 were homologous to genes in public protein databases. The remaining 211 selected clones had no significant amino acid sequence similarities with those deduced from any reported genes, though 62 of them appeared in Arabidopsis expressed sequenced tags (ESTs). About 40% of the selected clones were novel, validating the present approach for gene discovery. Northern blot analysis of 22 randomly selected clones confirmed that most were expressed preferentially in inflorescence tissues. In addition, many clones were transcribed at relatively low levels. We demonstrate that the screening method of the present study is useful for systematic classification of cDNA species based on expression specificity.