颗粒体病毒离体复制

迄今 ,尚未建立稳定的颗粒体离体复制系统 ,颗粒体病毒在离体复制中的研究仍处于探索阶段。就颗粒体病毒离体复制的研究进展进行了综述 ,主要包括影响颗粒体病毒离体复制的细胞类型 ,培养温度以及颗粒体病毒离体复制的作用机理和目前仍存在的问题。     

体细胞核移植与中心体遗传

体细胞克隆虽然在多种哺乳动物中成功获得后代, 但仍存在一系列的问题需要解决。克隆胚胎的发育能力由核移植后几小时内的细胞和分子过程决定, 包括染色体分离和纺锤体的重新组装。中心体的正常组成和分布能保证染色体分离的准确性及新生和出生后克隆动物发育过程中的基因组稳定性。文章在分析哺乳动物体细胞克隆存在的问题和简介中心体结构功能的基础上, 综述了中心体在配子和受精卵发育过程中的遗传机制, 同时阐述了体细胞克隆胚胎中心体及其相关蛋白的研究现状。     

埃立克体与埃立克体病

埃立克体病(Ehrlichiosis)是一种人兽共患自然疫源性疾病,其病原体--埃立克体(Ehrlichiae)是一类严格寄生在单核细胞、粒细胞及血小板内的革兰阴性菌.     

外切体研究进展

外切体是酿酒酵母中鉴定的一个保守复合体,具有3′外切核酸酶的活性.10个核心亚基,除Csl4p/Ski4p外,在体外都具有3′外切核酸酶的活性.外切体在多种RNA的代谢中起重要作用.外切体普遍存在于真核生物中,并与真核基因的表达调控密切相关.     

噬藻体

藻类细胞的溶解现象,无论在自然界或者实验室中早已引起人们的注意,但病毒性溶解因子直到1963年才首次在蓝藻中得到证实。十几年来,有关这类病毒的研究报告和综述已近200篇。在这些文献中采用了藻病毒(Phycoviruses),蓝藻病毒(Blue-green viruses,Cyanoviruses)、噬蓝藻体(Cyanophage)、噬藻体(Algophage)等名称。鉴于这类病毒与噬菌体之间若干相似性,同时在红藻、绿藻、褐藻和轮藻中也有类似病毒颗粒的报道,我们认为采用噬藻体为宜,它既反映了病毒本身的特点,也包括了它们宿主的性质。     

落叶松体胚发育中5个miRNA前体与成熟体的表达

利用同源比对或RACE克隆了5个落叶松(Larix leptolepis) miRNA前体。结果显示, 在各物种miRNA前体间, 成熟序列高度相似, 但其它序列相似度差异大, 序列相似度与亲缘关系有关。采用qRT-PCR分析了5个miRNA、前体和靶基因在落叶松体胚8个发育阶段的表达变化。结果显示, miRNA表达最高峰出现在后期子叶胚, 暗示与促进胚胎休眠有关; 表达次高峰出现时期不同, 表现为miR397和miR408在PEMIII, miR398在早期单胚, miR156和miR166在早期子叶胚, 表明其与保持薄细胞壁、质子传递、顶端分生组织形成等调控有关。miRNA成熟体表达与前体含量不呈线性相关, 可能受多重调控。研究结果对于阐明MIR基因进化、表达调控及在体胚发育中的调控功能具有重要理论意义。     

随体DNA不是指随体中的DNA

随体(satellite)是细胞中的一个结构成分,指某些染色体远端前的一小段,是一小段染色体,一般也是一个核仁组织区.随体DNA(Satellite DNA),则是指在DNA密度梯度离心时,处于卫星带中的DNA.真核生物的核内DNA,在CsCl或Cs_2SO_4中进行密度梯度离心时,除了形成一个主带(main band),即包含大部分DNA的分带外,往往在主带较轻或较重的一边还有一个或几个副带,称卫星带(satellite band).一般地,随体DNA(处于卫星带中的DNA)是高度重复DNA. 随体既然是一小段染色体,其中当然就有DNA.     

植物硅酸体

早在1804年,国外有人发现植物体内含有硅成分。以后,植物从土壤中吸收硅的习性逐渐获得了植物界的公认。而最早发现硅酸体的是微体化石研究的先驱者埃雷伯(Ehreberg1866年),他把空气中的尘土及雨水、泥炭、硅藻土中不同形态的硅酸体进行了分离,发现它们不同于动物硅酸盐骨胳化石,也不同于天然     

Darkness improves growth and delays necrosis in a nonchlorophyllous habituated sugarbeet callus: Biochemical changes

The transfer of light-cultured green normal (N) and white habituated (HNO) sugarbeet callus to darkness reduced the growth of N callus and improved growth and delayed necrosis in the HNO callus. The decrease of dry matter of N callus under darkness was accompanied by a reduced content of carotenoids and by decreased CO₂ fixation, which was compensated by an increased dependency on externally supplied sucrose. The levels of some organic nitrogen compounds such as glutamate, proline, and free polyamines were not affected by transfer to darkness of N or HNO callus. Darkness decreased ethylene emissions in both callus types. In the HNO callus, the sucrose growth dependency and the CO₂ fixation were unaffected by darkness. Chlorophylls were absent both in light and darkness, whereas some carotenoids were accumulated in the HNO callus only in dark conditions. In another connection, a significant increase of peroxidase activity, which did not occur in the N callus, was induced by darkness in the HNO callus. A decreased content of thio-barbituric acid (TBA)-reactive substances was measured in the HNO callus transferred to darkness, whereas an increase was noticed in the N callus placed in the same conditions. These metabolic changes and the reduction of cellular damage in darkness revealed light-induced stress reactions leading to necrosis and to reduced growth of HNO callus. It appeared that darkness allowed the HNO callus to avoid the photooxidation stress. Therefore, the favorable effect of darkness on HNO growth might be explained by the suppression of photooxidative damage due to the absence of carotenoids. The higher peroxidase activity in the HNO callus maintained in darkness raised the problem of heme synthesis in this heterotrophic callus.     

激素等外源物质对马铃薯愈伤组织花色苷积累的影响

从来源于马铃薯(Solanum tuberosum cv.Chieftain)茎的愈伤组织中分离到白色和红色2种愈伤组织,用鲜重法和分光光度法分别测量愈伤组织的生长量和花色苷的含量,并对激素、抗菌素和糖对马铃薯愈伤组织生长和花色苷积累的影响进行研究。结果表明:低浓度的2,4-D有利于红色愈伤组织的花色苷积累,高浓度的2,4-D促进其生长而不利于花色苷的积累;高浓度的6-BA能促进红色愈伤组织中花色苷的积累并诱导白色愈伤组织花色苷的合成,但抑制其生长;卡那霉素能使白色愈伤组织变红并积累花色苷,高浓度的卡那霉素严重抑制愈伤组织的生长并最终变褐死亡;提高蔗糖浓度能促进愈伤组织花色苷的产生和积累,但超过70g/L时抑制生长。实验结果为今后花色苷生物合成机理研究和花色苷的工厂化生产奠定了基础。     

芦苇胚性愈伤组织的形成及植株的再生

以芦苇种子为外植体,其愈伤组织的诱导率最高。叶鞘和叶片不发生脱分化。培养基中最合适的蔗糖浓度为4%。维生素 B 类、肌醇对愈伤组织的生长起促进作用。而酵母提取物对愈伤组织的诱导和生长具有明显的抑制作用。这种抑制效应,将随酵母提取物浓度的提高而增大。愈伤组织的继代培养,随培养基中2,4-D 浓度的提高,其平均鲜重明显降低。脱分化培养基中2,4-D 浓度对胚性愈伤组织的诱导形成具有一定的相关性。胚性愈伤组织经30代继代培养依然具有90%的分化频率,只是每块愈伤组织的分化苗数减少。反之,非胚性愈伤组织则完全丧失形态发生的能力。对两类愈伤组织进行扫描电镜的观察,发现其表面结构有很大差异。其过氧化物酶、酯酶同工酶谱以及可溶性蛋白的含量均有明显的差别。     

籼型杂交稻亲本成熟胚愈伤组织再生体系的建立

本文给出了6个籼型杂交稻亲本成熟胚愈伤组织再生体系建立优化措施。采用6个有重要育种价值的杂交籼稻亲本成熟胚盾片诱导愈伤组织作为分化再生的外植体,通过调节2,4-D浓度、培养基成分、接种方式、激素组合和愈伤组织分化途径,建立适合籼稻遗传转化的再生体系。结果表明,MB培养基是较为合适的愈伤组织诱导培养基类型,6个品种在MB培养基上的愈伤组织诱导率均在60％-80％之间。半粒米的接种方式能够明显提高愈伤组织诱导率,提高幅度达到28．2％。通过调节2,4-D浓度和激素组合,愈伤组织诱导率最高可达到97．9％,两步分化法和适当干燥处理能够提高愈伤组织的分化效率,6品种愈伤组织分化率均在50％-90％之间。初步建立了6个杂交籼稻亲本品种成熟胚愈伤组织的再生体系,为以后遗传转化奠定基础。     

Embryogenic Callus Formation and Plantlet Regeneration of Piragmites communis

The present paper reports the embryogenic callus formation and plantlet regeneration of Phragmites communis. The results have been obtained as follows: The efficiency of callus induction was much higher, if reed seeds were used as explants. No dedifferentiation was observed by using leaf sheath and leaf blade as explants. The optim, um concentration of sucrose was 4% in medium. VB group and inositol had beneficial effects on callus growth. But yeast extract inhibited callus induction and callus growth markedly. For this inhibited reaction, the higher concentration, the more obviously the callus growth was inhibited. Higher levels of 2,4-D had unfavourable effects on callus growth in callus subculture. The concentration of 2,4-D in dedifferentiation medium had relation to embryogenic callus formation. Embryogenic callus had higher frequency of differentiation for long-term subculture. On the other hand, nonembryogenic callus most often lost their morphogenetic competence. Authors found that the surface structure of the two types of calluses was different by means of observation by scanning electron microscope. The peroxidase and the esterase isoenzyme pat- terns, as well as the soluble protein of both types of calluses were different too.     

Plant regeneration from tissue cultures of Pokkali rice is promoted by optimizing callus to medium volume ratio and by a medium-conditioning factor produced by embryogenic callus

The frequency of plant regeneration from seed-derived Pokkali rice callus has been substantially increased. Four conclusions were drawn from the study: (1) Non-embryogenic callus consisting of elongated, highly-vacuolated cells did not produce regenerated plants. Embryogenic callus consisting of small, non-vacuolated cells produced somatic embryos and regenerated plants. (2) The numbers of plants could be markedly increased by optimizing a medium for embryogenic callus production and a second medium for plant regeneration from embryogenic callus. (3) The optimization of callus to medium volume ratio of 6.5 mg embryogenic callus per 1.0 ml of medium significantly increase plant production on regeneration medium. (4) A further significant increase was obtained by using regeneration medium previously conditioned for one or two weeks by optimal amounts of embryogenic callus. At present, the callus derived from a single seed in six months could theoretically be used in the seventh month to produce 127500 plants.This research was supported by the Agency for International Development under Contract No. AID/DSAN-C-0273     

Synthesis and secretion of alpha-amylase by rice callus: evidence for differential gene expression

Rice seed callus expressed and secreted alpha-amylase at high levels. Twenty percent of the protein secreted by the callus was alphaamylase. The callus secreted about 840 mug alpha-amylase with 10.9 x 10(3) units of activity per gram dry weight callus per day. The alpha-amylase from callus exhibited a more complex isoform pattern than the germinating seed alpha-amylase. In addition, the level of mRNA expression by the five alpha-amylase gene groups was markedly different between callus and the germinating seed. The rice callus culture has features which it attractive as a potential system for expression proteins in plant cell fermentation systems.     

Callus cultures for phytometabolism studies: phytometabolites of 3-trifluoromethylphenol in Lemnaceae plants and callus cultures

Plant callus cultures have the potential to advance phytoremediation science by allowing study of cellular phytometabolism in absence of sorption, translocation, microbial degradation, and other phytoremediation processes; however, studies demonstrating the applicability of results from callus cultures to whole plants are limited. The aim of this study was to evaluate the feasability and applicability of using callus cultures to study phytometabolism. This aim was accomplished through evaluation of induction and growth of Lemnaceae callus cultures and comparison of phytometabolism in callus cultures and whole plants. Four out of eight published methods for callus culture of Lemnaceae successfully induced callus cultures that exhibited doubling times of 1.7 to 23 wks. Callus cultures and whole plants of Landoltia punctata and Lemna minor metabolized 3-trifluoromethylphenol (3-TFMP) through conjugation with glucopyranoside, malonyl-glucopyranoside, and glucopyranosyl-apiofuranoside. However, concentrations of metabolites were approximately 10 times less in callus cultures than in plants. While results demonstrated applicability of callus cultures results to whole plants, the low success rate of callus induction procedures, length of time required to produce substantial callus mass, and the low accumulation of metabolites in callus cultures may limit the feasibility of callus cultures for assessing phytometabolism.     

Induction and characterization of embryonic callus types for the initiation of suspension cultures of leek (Allium ampeloprasum L.)

In this paper the development and characterization of a friable, embroyonic callus culture of leek is described. This callus type was initiated on immature embryos and differed in appearance from formerly induced compact, embryogenic callus [4]. The friable callus was comprised of numerous globular embryoids, embedded in a mucilaginous substance. The genotype of the donor plant and the embryo size were important parameters in the initiation of this callus type. Embryos of 0.5–2.5 mm gave the highest frequency of friable callus production. The basal media and inclusion of -proline into the media did not influence the friable callus production. Light microscopic comparison of compact and friable callus showed striking differences. Compact callus consisted of a meristematic zone and contained vascular elements. Friable callus was less differentiated and contained aggregates of embryonic cells, separated by intercellular spaces, and somatic embryos. Ten independently induced friable callus cultures were tested for their amenability to form suspension cultures. From one of these, two highly embryonic suspension cultures were selected.     

Sorbitol as the Primary Carbon Source for the Growth of Embryogenic Callus of Maize

The effects of various carbon sources on initiation and maintenance of embryogenic callus of maize (Zea mays L.) and on the regeneration of plants from embryogenic callus were studied. Growth of embryogenic callus tissue on media containing sucrose was typified by the subsequent growth of both embryogenic (regenerable) and nonembryogenic (nonregenerable) callus. Growth of embryogenic callus on sorbitol was unique among the carbon sources tested in that sorbitol supported the subsequent growth of only embryogenic callus. Further experiments demonstrated that embryogenic callus grown on sorbitol had a greater regenerative capacity (more plants produced per gram fresh weight of callus) than callus grown on sucrose. Sorbitol dehydrogenase was detected in embryogenic callus of maize at a specific activity roughly equivalent to that found in zygotic embryos of developing seeds. Nonembryogenic callus did not contain significant levels of sorbitol dehydrogenase activity.