Introns in higher plant genes

The intron is an important component of eukaryotic gene. Extensive studies have been conducted to get a better understanding of its structure and function. This paper presents a brief review of the structure and function of introns in higher plant genes. It is shown that higher plant introns possess structural properties shared by all eukaryotic introns, however, they also exhibit a striking degree of diversity. The process of intron splicing in higher plant genes involves interaction between multiple cis-acting elements and trans-acting factors, such as 5′ splicing site, 3′ splicing site and many protein factors. The process of intron splicing is an important level at which gene expression is regulated. Especially alternative splicing of intron can regulate time and space of gene expression. In addition, some introns in higher plant genes also regulate gene expression by affecting the pattern of gene expression, enhancing the level of gene expression and driving the gene expression.     

基于多维伪F统计量的基因表达动态聚类分析方法研究

K-均值聚类分析算法是一种广泛应用于基因表达数据聚类分析中的迭代变换算法，它通过指定类别数K-基于给定的聚类目标函数，并采用迭代更新的方法，使得最终的聚类结果的目标函数值为极小值，达到较优的聚类效果。针对K-均值聚类分析算法存在参数依赖性强，且在整个聚类过程中类的数目无法改变的缺点，引入动态调整聚类个数的思想和多维伪F统计量，提出了一种基于多维伪F统计量的基因表迭动态K-均值聚类算法。实验结果表明该算法可以动态调整聚类个数，给出最佳聚类数目，从而获得较好的聚类质量．     

水稻基因表达谱分析寡核苷酸芯片制备的研究

 首先有目的地搜集了50个水稻花序相关基因,进行了探针的设计、筛选及合成纯化,用点样仪以微阵列的形式将其点于醛基化的玻璃片上;将3个不同生长阶段的水稻花序材料的总RNA经荧光标记反转录后与寡核苷酸芯片进行杂交.用ScanArray3000对获得的表达谱进行扫描分析显示,芯片图像背景均匀,信号清晰.用ImaGene4.0软件对表达谱分析表明,候选基因在水稻花序3个不同发育阶段的材料中,表达水平有显著差异.为进一步进行水稻寡核苷酸芯片的制备及应用奠定了基础.     

5种细胞周期调控基因在小鼠生殖细胞发育过程中的表达研究

 以成熟(10周龄以上)的昆明种正常小鼠的精巢和卵巢为材料,利用地高辛标记的基因探针进行组织切片上的DNA-mRNA分子原位杂交,研究了PCNA,cdc2,cyclin D1,p2 1和 p16 5种细胞周期调控基因在生殖细胞发育过程中的表达.结果表明:PCNA基因在睾丸组织的精原细胞和精母细胞中有强杂交信号,而在雌性生殖细胞及滤泡细胞的发育过程都没有杂交信号;cyclin D1,cdc2,p2 1,p16基因在生殖细胞的发育过程中都没有,表明这些基因并没有参与小鼠生殖细胞的生长和分化调控.这些事实表明在生殖细胞发育过程中,控制细胞增殖和增殖抑制的基因与培养细胞有不同的机制,它们可能采用了不同的调控系统.     

花生根瘤菌转吸氢基因的研究

以ｐＲＫ２０７３为辅助质粒、通过三亲本杂交，将携带豌豆根瘤菌吸氢基因的质粒ｐＡＬ６１８转移到花生根瘤菌ＮＢ２中，通过抗性筛选、质粒检测及吸氢活性测定，获得一系列能稳定遗传的结合株，其中ＮＢ２－７，ＮＢ２－１１在自生条件下其吸氢活性为受体株的１５倍，在共生条件下其吸氢活性为受体株的２～３倍．     

Possible developmental mechanisms underlying the origin of the crown lineages of arthropods

The extraordinarily preserved, diverse arthropod fauna from the Lower Cambrian Maotianshan shale, central Yunnan (southwest China), represents different evolutionary stages stepping from stem lineages towards crown arthropods (also called euarthropods), which makes this fauna extremely significant for discussion of the origin and early diversification of the arthropods. Anatomical analyses of the Maotianshan shale arthropods strongly indicate that     

Pathogenesis of Plasmodium falciparum malaria: the roles of parasite adhesion and antigenic variation

Malaria results in up to 2.5 million deaths annually, with young children and pregnant women at greatest risk. The great majority of severe disease is caused by Plasmodium falciparum. A characteristic feature of infection with P. falciparum is the accumulation or sequestration of parasite-infected red blood cells (RBCs) in various organs, such as the brain, lung and placenta, and together with other factors is important in the pathogenesis of severe forms of malaria. Sequestration results from adhesive interactions between parasite-derived proteins expressed on the surface of infected RBCs and a number of host molecules on the surface of endothelial cells, placental cells and uninfected RBCs. Some receptors for parasite adhesion have been implicated in particular malaria syndromes, such as intercellular adhesion molecule 1 in cerebral malaria and chondroitin sulfate A and hyaluronic acid in placental infection. The principal parasite ligand and antigen on the RBC surface, P. falciparum erythrocyte membrane protein 1 encoded by a multigene family termed var, is clonally variant, enabling evasion of specific immune responses. An understanding of these host-parasite interactions in the context of clinical disease and immunity may reveal potential targets to prevent or treat severe forms of malaria. Received 25 June 2001; received after revision 22 August 2001; accepted 24 August 2001