Expression of the pX gene of HTLV-I: general splicing mechanism in the HTLV family

Human T-cell leukemia virus type I (HTLV-I) is an etiological agent of adult T-cell leukemia. A viral gene pX encodes for p40X and it has been proposed that this protein trans-activates the viral long terminal repeat and possibly some cellular genes; this activation may be associated with T-cell transformation. The mechanism of pX gene expression and the primary structure of p40X are now reported. Two-step splicing generates the 2.1-kilobase pX mRNA; the initiator methionine for env becomes part of the pX protein. These splicing signals are conserved among all members of the HTLV family except for the acquired immune deficiency syndrome-associated viruses.     

Expression of a bacterial gene in mammalian cells

Transfection of cultured monkey kidney cells with recombinant DNA constructed with a cloned Escherichia coli gene that codes for xanthine-guanine phosphoribosyltransferase and several different SV40 DNA-based vectors, results in the synthesis of readily measurable quantities of the bacterial enzyme. Moreover, the physiological defect in purine nucleotide synthesis characteristic of human Lesch-Nyhan cells can be overcome by the introduction of the bacterial gene into these cells.     

Changing sensitivity of the pubertal gonadal hypothalamic feedback mechanism in man

Clomiphene citrate in doses which stimulate gonadotropin production in the adult suppresses urinary follicle stimulating hormone (FSH) excretion and plasma testosterone concentration in prepubertal children. Such results indicate that feedback between gonad and hypothalamus is operative and highly sensitive in prepubertal humans. Puberty in man, as in the rat, is accompanied by a decrease in the sensitivity of the feedback mechanism.     

一对单显性大豆抗疫霉根腐病基因的遗传分析及定位

[目的]大豆疫霉根腐病是大豆毁灭性的病害之一,防治该病最安全有效的方法是培育和利用抗性品种。迄今为止,已在大豆基因组上鉴定了21个大豆疫霉根腐病抗性基因,但是在中国只有少数基因(如Rps1c、Rps1k等)抗性有效。因此,急需发掘新的大豆疫霉根腐病抗性基因,以满足抗病育种的需要。‘大方六月早’对大豆疫霉菌的抗谱较广,是目前筛选出的优异抗源。[方法]采用下胚轴创伤接种方法进行抗病性鉴定,以品种‘大方六月早’为抗病亲本与品种‘矮脚早’配置杂交组合获得F2∶3代家系群体,并进行遗传分析,通过SSR(simple sequence repeat)标记对‘大方六月早’的抗性基因进行定位。[结果]该群体的抗性遗传分析表明:‘大方六月早’对大豆疫霉根腐病的抗性由1对主效基因控制,抗病对感病表现为显性,暂命名为RpsAH。使用SSR标记进行分子作图,抗病基因RpsAH被定位在大豆3号染色体(即N连锁群)上,距离标记Sat_166为4.1 cM。[结论]大豆品种‘大方六月早’对大豆疫霉菌株AH的抗性由1个单显性基因控制,该基因定位于大豆分子遗传图谱N连锁群上。     

玉米显性高油基因存在的若干证据

通过来源不同的20个高油系和5个普通系杂交当代和后代籽粒油分花粉直感效应及遗传分离特点分析，发现N1680高油系的杂交当代籽粒和F2籽粒油分含量接近于高油亲本，表现出显性基因的遗传特征；同时，F2籽粒油分还存在明显的超高亲优势。因此推测该系可能存在显性高油基因，并与其他基因存在互作效应。     

The gene for familial polyposis coli maps to the long arm of chromosome 5

The inherited genetic defect in adenomatous polyposis has been localized to a small region on the long arm of chromosome 5. Sixteen DNA marker loci were used to construct a linkage map of the chromosome. When five kindreds segregating a gene for adenomatous polyposis coli were characterized with a number of the markers, significant linkage was found between one marker and the disease gene. Linkage analysis determined the location of the defective gene within a primary genetic map of chromosome 5.     

Expression of the Escherichia coli lacZ gene on a plasmid vector in a cyanobacterium

A biphasic plasmid vector was used to introduce the Escherichia coli K-12 lac operon into the unicellular cyanobacterium Agmenellum quadruplicatum PR-6. The PR-6 transformants expressed beta-galactosidase at nearly as high a level as did Escherichia coli transformants. In order to accomplish this, it was necessary to obtain PR-6 mutants that could be transformed by plasmids with unmodified recognition sites for the endogenous PR-6 restriction endonuclease Aqu I. These mutants were generated by a variation of the ectopic mutagenesis techniques that have been used in other naturally transforming bacteria. The ability to assay the expression of lacZ in PR-6 paves the way for the construction of gene fusions with various PR-6 promoters and quantitation of their expression under specific in vivo conditions.     

Thyrocalcitonin: evidence for release in a spontaneous hypocalcemic disorder

Thyrocalcitonin content of thyroid gland extracts from normal postparturient cows was 3.9 times greater than in cows with postparturient paresis. The parafollicular cells in diseased cows were less numerous and appeared to have discharged their secretory products. An abrupt release of thyrocalcitonin near parturition may be related to the development of the hypocalcemia and hypophosphatemia in this disorder.     

A general mechanism for network-dosage compensation in gene circuits

Coping with variations in network dosage is crucial for maintaining optimal function in gene networks. We explored how network structure facilitates network-level dosage compensation. By using the yeast galactose network as a model, we combinatorially deleted one of the two copies of its four regulatory genes and found that network activity was robust to the change in network dosage. A mathematical analysis revealed that a two-component genetic circuit with elements of opposite regulatory activity (activator and inhibitor) constitutes a minimal requirement for network-dosage invariance. Specific interaction topologies and a one-to-one interaction stoichiometry between the activating and inhibiting agents were additional essential elements facilitating dosage invariance. This mechanism of network-dosage invariance could represent a general design for gene network structure in cells.     

Human thymidine kinase gene locus: assignment to chromosome 17 in a hybrid of man and mouse cells

The human chromosome retained in a hybrid clone derived from human cells and a moluse line deficiemt in thymidine kinase has the quinacrinefluorescence pattern characteristic of chromosome 17.     

形成灰色烤烟的原因及机理

通过对土壤、烟株、烟叶生理生化指标分析及田间生态环境调查和盆栽试验,系统研究了形成灰色烤烟的原因及影响品质的机理.结果表明,烤烟灰色烟叶发生与植烟土壤pH偏低、根层土壤含水量过高、土壤通透性差有密切关系,而影响灰色烟叶发生和严重程度的直接原因是土壤和烟叶内Fe,Mn等离子含量过高所致.在土壤pH值偏低,土壤含水量过高,根层土壤通透性差的条件下,Fe,Mn由不易被吸收的高价态转化成容易被植物吸收的低价态,造成烟株体内吸收积累Fe,Mn过多,营养平衡失调,引起烟草出现生理性中毒.     

利用染色体片段代换系定位一个水稻显性早熟基因

以水稻染色体片段代换系构建的分离群体为材料,利用微卫星标记(Simple sequence repeat,SSR)定位一个生育期基因,对水稻生育期基因的分子标记辅助选择进行了研究.结果表明,早熟显性基因(暂命名为Hd10-1)定位于第10染色体,SSR标记RM271和RM258之间,与RM 271的遗传距离为1.90 cM,与RM 258的遗传距离为8.40 cM,RM 271与RM 258位于Hd10-1的两侧.     

一个水稻CCCH型锌指蛋白基因的表达模式分析

利用RT-PCR、生物信息学及其启动区与GUS基因的融合表达分析等方法,分析了一个水稻CCCH型锌指基因OsZF77的表达模式。OsZF77开放阅读框包含843个核苷酸,编码280个氨基酸,含有2个CCCH锌指结构域。RT-PCR分析表明该基因在水稻种子的胚乳中具有较高丰度的表达而在胚中不表达。对OsZF77上游2．5kb左右的启动子区段进行分析发现含有种子特异性表达必需的序列元件RY（CATGCATG）。进一步分析了该基因启动子区段与GUS基因融合表达载体的转基因水稻植株,结果表明GUS在种子胚乳特别是靠种皮的外围胚乳中具强表达,而在胚中检测不到GUS活性。以上结果说明该基因是一个胚乳优势表达基因。     

Methylation of an immediate-early inducible gene as a mechanism for B cell tolerance induction

Stage-specific gene regulation is important in determining cell function during development. Immature B cells expressing membrane-bound immunoglobulin M (mIgM) are sensitive to antigen-induced tolerance, whereas mature B cells are activated by antigen. Previous studies have established an association between Egr-1 gene induction and antigen receptor (mIgM)-mediated activation of mature B cells. Here it is shown that the immature B cell line WEHI-231 and tolerance-sensitive bone marrow-derived B cells do not express Egr-1. It is further shown that lack of inducible expression in these cells is due to specific methylation of the Egr-1 gene. Thus, covalent inactivation of an activation-associated gene may explain tolerance sensitivity at specific stages of B cell development.     

Mobility gaps: a mechanism for band gaps in melanins

The semiconductor behavior of melanins is reviewed and compared with quantum mechanical models of conduction in amorphous solids. The available data are consistent with extensions of Mott's basic model for amorphous semiconductors, whereas they are inconsistent with crystalline semiconductor models. An investigation of the specific conduction mechanisms operative in melanins in terms of the amorphous model should reveal important aspects of the band structure.     

小麦耐高温特性的生理机制与基因挖掘研究进展

高温是小麦生产上经常发生的一种非生物逆境,严重影响小麦产量和品质形成。研究小麦耐高温的生理机制,挖掘小麦耐高温基因一直是国内外研究的重点和热点。文章总结了高温对小麦光合作用、细胞膜稳定性、渗透调节物质含量、活性氧清除系统活性、叶绿素合成等生理性状的影响;归纳了已定位的耐高温相关性状QTL,包括穗数、穗粒数、千粒重等产量相关性状,可溶性糖含量、冠层温度、叶绿素含量、叶绿素荧光参数等生理相关性状;概括了已发现可提高小麦耐高温特性的基因,主要为小麦耐高温相关转录因子。针对目前小麦耐高温功能基因研究相对滞后的现状,提出今后应加强耐高温小麦新材料创制和耐高温表型精准鉴定技术体系构建研究,为耐高温基因挖掘与新品种培育提供坚实的材料与技术支撑;以六倍体小麦参考基因组序列释放为契机,加快小麦耐高温基因克隆进程,为耐高温小麦新品种培育提供基因资源;加强基因编辑与转基因技术在小麦耐高温育种中应用,实现对小麦耐高温特性的精准定向改良。