苹果Ty1-copia类逆转座子家族鉴定及特性分析

根据逆转座子RT保守序列设计引物,利用PCR方法从苹果'嘎拉'中克隆了20条RT片段,分析苹果基因组内Ty1-copia类逆转座子家族特性及进化关系.结果显示,20条逆转录酶保守序列表现出了高度的异质性.结合已报道的37条苹果Ty1-copia类逆转座子RT片段,构建了系统发育树,发现家族1、3和4中具有转座活性的逆转座子的可能性较大;序列分析表明,Ty1-copia类逆转座子是苹果基因组内序列重组的热点.用RT序列为探针进行Southern杂交,发现苹果基因组内Ty1-copia类逆转座子拷贝数高、分布广泛.研究结果为进一步分离具有转座活性的苹果Ty1-copia类逆转座子及其人工诱导芽变奠定了基础.     

节瓜Ty1-copia类逆转座子逆转录酶序列的克隆及比对

对8个节瓜（Benincasa hispida var.chieh-qua How）品系基因组DNA中的Ty1-copia类逆转座子逆转录酶核苷酸序列进行扩增,并对品系A39FA的29个克隆产物的核苷酸序列及翻译的氨基酸序列的系统进化和同源性进行了分析,还对29条氨基酸序列进行了比对。扩增结果表明：8个节瓜品系的基因组DNA中均包含长度约260 bp的逆转录酶核苷酸片段;从品系A39FA中获得的29条Ty1-copia类逆转座子逆转录酶核苷酸序列（CqRt1至CqRt29）的长度为247~267 bp,同源率为46.2%~98.1%,而它们的氨基酸序列同源率为26.7%~98.8%。序列分析结果表明：节瓜Ty1-copia类逆转座子逆转录酶核苷酸序列中碱基A、T、G和C的数量分别为65~96、47~92、45~74和32~49,所有序列均富含碱基A和T,AT/GC比为1.35~2.33;缺失突变是造成节瓜Ty1-copia类逆转座子逆转录酶核苷酸序列长度差异的主要因素,在序列长度和碱基组成方面的明显差异表明节瓜Ty1-copia类逆转座子逆转录酶核苷酸序列具有高度异质性。翻译后的氨基酸序列中有21条序列存在终止密码子突变、12条序列存在移框突变,表明Ty1-copia类逆转座子是节瓜基因组内序列重组的热点。通过聚类分析可将29个逆转录酶核苷酸序列分为5个家族（Family）,分别包括16、4、4、4和1条序列,其中Family 1可能是具有转座活性的逆转座子家族,但存在转录活性的逆转录酶序列仅占全部序列数量的20.69%。将每一家族中的1~2条序列与其他15种植物的Ty1-copia类逆转座子逆转录酶的氨基酸序列进行比对,显示出较高的同源性。研究结果表明：节瓜与其他植物的Ty1-copia类逆转座子可能有相同起源,而且Ty1-copia类逆转座子可在不同类群间横向传递。     

甘薯与牵牛EST资源的SSR信息分析

为挖掘番薯（Ipomoea）属EST-SSR资源,从NCBI数据库下载23406条甘薯（Ipomoea batatas (L.) Lam.）EST和62282条牵牛（Ipomoea nil (L.) Roth）EST,利用生物信息学软件预处理、去冗余、拼接处理后得到12812条无冗余的甘薯EST（6.70 Mb）和28422条牵牛唯一序列（17.19 Mb）。对这些序列进行SSR搜索,在甘薯上获得328个SSR位点,发生频率为2.56%;牵牛上筛选到962个SSR位点,出现频率为3.38%。甘薯和牵牛EST-SSR具有多个共同特征：在SSR位点中,主要是二核苷酸重复类型,其次是三核苷酸重复;在二核苷酸重复中,出现最多的重复基序为AG/CT,其次是AT/AT;在三核苷酸重复中,主要基序是AAG/CCT;SSR位点的长度主要集中在20~22 bp。结果表明,这些搜索出的EST-SSR重复基序类型丰富、多态性潜能高,具有较高的开发和利用价值。     

裸燕麦Ty1-copia类反转录转座子反转录酶序列的分离、鉴定与分析

本研究根据Ty1-copia类反转录转座子反转录酶的保守区设计简并引物,通过PCR扩增,从裸燕麦(Avena nuda L.)品种‘品燕1号’基因组中分离获得23条Ty1-copia类反转录转座子序列,并对序列特征、系统发育关系及其转录活性进行分析。结果显示,23条Ty1-copia类反转录转座子存在较高的异质性,序列间的一致性为45%～98%,存在插入、移码和终止密码突变,但频率不高;系统发育分析结果表明,燕麦Ty1-copia类反转录转座子在进化过程中主要为垂直传递。本研究通过检索燕麦基因表达数据库,发现了5个有转录活性的Ty1-copia类反转录转座子。     

Heritability of regeneration in tissue cultures of sweet potato (Ipomoea batatas L.)

Summary A population of open-pollinated progeny from 12 parents, and the 12 parents, was surveyed for in vitro growth and regeneration characteristics. Four different tissue culture procedures involving different media and the use of different explants to initiate the cultures were used. Petiole explants from young leaves were used as explants for initiation of callus cultures. These were evaluated for callus growth rate, friability, and callus color and texture, before transferring to each of three different regeneration media for evaluation of morphogenetic potential. Small shoot tips also were used to initiate callus cultures, which were evaluated for the same growth characteristics and transferred to growth-regulator free regeneration media. Regeneration occurred through root or shoot regeneration or through embryogenesis. Tissue culture treatment effects, as well as genotypic effects, were highly significant in determining: the types of callus produced, callus growth rates, color and texture on the two types of media used for the second and third subcultures. The family x treatment interaction was generally not statistically significant, affecting only callus color. Estimates of narrow sense heritability for callus growth rate in both the second and third subcultures were high enough (0.35 and 0.63, respectively) for the evaluation of parental lines for selection procedures. These characteristics were also the only early culture callus traits that were consistently correlated with later morphogenesis of the cultures. They were negatively correlated with root or shoot regeneration. The occurence of somatic embryogenesis was not correlated with early callus growth characteristics. Genetic and treatment effects were highly significant in the evaluation of morphogenetic potential, through root or shoot regeneration, or through embryogenesis. Regeneration of all types was of low frequency for all procedures, expressed in 11% of the cultures of the total population.Paper No. 9906 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601, USA. From a thesis submitted by the senior in partial fulfillment of the requirements for the Ph.D. degree     

甘薯基因组 TCP转录因子鉴定与逆境胁迫表达分析

基于甘薯( Ipomoea batatas ( L.) Lam.)全基因组序列, 利用生物信息学方法鉴定筛选了全基因组中的TCP( teosinte branched1/cincinnata/proliferating cell factor)转录因子, 并分析了甘薯苗期在蔓割病菌胁迫及块根储藏期低温胁迫下TCP基因的...     

Growth and morphogenesis of immature embryos of sweet potato (Ipomoea batatas L.) in vitro

Sweet potato (Ipomoea batatas L.) embryos excised from the fertilized ovules of 6- to 12-day-old capsules were cultured on MS medium supplemented with NAA, BA, GA separately and in combinations. GA was found essential for initial morphogenesis of globular and heart stages. Seedlings were recovered from late globular stage onwards but recovery was best from advanced embryo stages. Differentiated embryos produced multiple shoots on MS medium +1M NAA÷2M BA +0.5M GA.     

Design and synthesis of N1-aryl-benzimidazoles 2-substituted as novel HIV-1 non-nucleoside reverse transcriptase inhibitors

A series of novel N₁-aryl-2-arylthioacetamido-benzimidazoles were synthesized and evaluated as inhibitors of human immunodeficiency virus type-1 (HIV-1). Some of them proved to be effective in inhibiting HIV-1 replication at submicromolar and nanomolar concentration acting as HIV-1 non-nucleoside RT inhibitors (NNRTIs), with low cytotoxicity. The preliminary structure–activity relationship (SAR) of these new derivatives was discussed and rationalized by docking studies.     

Isozyme modifications and plant regeneration through somatic embryogenesis in sweet potato (Ipomoea batatas (L.) Lam.)

Summary The potential of somatic embryogenesis was evaluated for 10 cultivars of sweet potato through extensive embryogenic response and isozyme analysis. Embryogenic callus was induced by incubating lateral buds on Murashige and Skoog medium containing 10 M 2,4-dichlorophenoxyacetic acid for 6–8 weeks. The frequency of embryogenic response was low, and varied with genotypes, ranging from 0 to 17%. Embryo to plantlet formation could be enhanced by the use of the combination of 2,4-dichlorophenoxyacetic acid with kinetin, both used at 0.01 M. Embryogenic callus with its potential of plantlet formation has constantly been maintained for over two years. However, after several subcultures, 0.5 to 12% of embryogenic callus reverted irreversibly into friable fast-growing non-embryogenic callus whose ability to regenerate shoots was then definitively lost. The isozymes of esterase, peroxidase, glutamate oxaloacetate transaminase and acid phosphatase investigated in this study were found appropriate to distinguish compact embryogenic from friable non-embryogenic callus in sweet potato. In fact, the callus reversion was associated with a loss of bands or a decline in isozyme activity. On the contrary, very small changes in isozyme activity or no specific changes at all were observed during the differentiation of embryogenic callus into globular embryos.Abbreviations Acp acid phosphatase - BAP 6-benzylaminopurine - cv cultivar - df degree of freedom - 2,4-D 2,4-dichlorophenoxyacetic acid - Est esterase - Got glutamate oxaloacetate transaminase - IAA indole-3-acetic acid - MS Murashige and Skoog (1962) medium - Prx peroxidase - Tris tris(hydroxymethyl)aminomethane     

LINE-1编码的逆转录酶在肿瘤形成过程中的作用

逆转录转座子LINE-1是人类基因组中最大的转座子家族,约有500 000个拷贝,占人类基因组总量的17%,同时它也是人类基因组中唯一具有自主转座能力的转座子。LINE-1编码的逆转录酶是LINE-1转座所必需,近年来的研究表明该酶在包括肿瘤形成等重要的病理或生理过程中都发挥着重要的作用。抑制该酶的活性可阻滞肿瘤发展的进程、恢复肿瘤细胞的分化状态以及改变肿瘤细胞的转录组谱。本文根据近年来对LINE-1编码的逆转录酶的研究进展,介绍该酶通过对非编码RNA转录组谱的调控在肿瘤形成过程中产生的作用,以期为肿瘤的早期诊断以及抗肿瘤药物的开发提供一些线索。