突变质体随细胞分裂而传递的性质和规律初探

设一初始细胞中共有ｍ个质体,其中ｉ个是突变的,我们研究了它们随细胞分裂而分裂并在细胞间进行随机分配的过程中,一细胞分配ｍ个突变质体的概率。令ｘ（ｔ）＝１表示在第ｔ次分裂时,一细胞只含突变质体这一随机事件,ｘ（ｔ）＝０为其对立事件。我们得到了随机过程｛ｘ（ｔ）,ｔ∈Ｔ｝的一些性质、证明了该过程为一马尔可夫链,给出了细胞质内质体杂化（含突变与非突变两类质体）与质体纯化（仅含一类质体）两种状态之间的转移概率矩阵,揭示了突变质体随细胞分裂而传递的若干规律。     

在细胞含质体数目不均、分裂不同步条件下突变质体随细胞分裂而传递的模式

本文在细胞质体数目不均等、分裂不同步条件下建立了突变质体随细胞分裂而传递的数学表达式,并在具体给定条件下给出了具体计算原始细胞分裂n次后其子细胞含有x个质体,且其中已有j个质体发生突变的可能性（即概率）的公式。     

关于质体随细胞分裂传递的数学模型

本文根据质体是具有遗传功能的细胞器这一事实出发,对质体传递规律首次进行了定量研究,建立了突变质体在细胞分裂中传递的全概率和条件概率公式．并对此公式的应用作了进一步的探讨．本文所提供的方法将为质体遗传开辟一条定量研究的新路．     

两种裸藻的无叶绿体突变株

利用Ofloxacin处理获得了纤细裸藻和中型裸藻无叶绿体突变株。吸收光谱测定和自荧光显微观察证明突变株无叶绿素合成,DAPI染色方法显示突变株细胞不存在质体DNA,而无色的长变胞藻细胞中仍有可检测质体DNA,说明二突变株质体已消失。SDS－PAGE显示野生种和突变株各有特异蛋白表达。     

抗4-氧赖氨酸的烟草愈伤组织突变体质体超微结构的初步观察(简报)

用连续光照培养反复选择,从Wo分离出绿色(gy)与白色(W22)两系表现型。对OL的抗性和过氧化物酶同工酶酶谱两系未见显著差异。W22的赖氨酸含量较yg的低。yg的叶绿体含淀粉粒,同一细胞内未见含突变质体。在W22则未见叶绿体,而见造粉质体和突变的质体。     

被子植物质体遗传的细胞学研究

植物细胞质遗传涉及细胞质中含DNA的两种细胞器——质体和线粒体从亲代至子代的传递。相对来说线粒体遗传的研究远不及质体的多,这可能是线粒体这种细胞器缺乏合适的表型突变体之故。高等植物质体遗传的研究历史可追溯到本世纪初在杂交试验中对叶色遗传的非孟德尔定律的发现,Baur在马蹄纹天竺葵(Pelargonium zonale)中从叶色突变体(白化体)的杂交遗传分析,发现了双亲质体遗传;而Correns在紫茉莉(Mirabilis jalapa)中则发现了单亲母本质体遗传(见Kuroiwa)。此后,对质体基因组突变性状遗传分析的研究,大量的资料说明了在被子植物中存在双亲质体遗传和单亲母系质体遗传两种类型,而后一种占大多数,仅少数是比较有规律的为双亲质体遗传或偶尔是双亲质体遗传。几十年来应用遗传分析的方法对被子植物质体遗传的研究,着重于揭示不同植物种质体的遗传是单亲母系或是双亲质体传递,以及探索杂种核基因对质体传递方式的影响。     

烟草缺绿突变体的质体发育和超微结构

用电子显微镜对烟草白化突变体的叶片细胞进行了观察。发现白化苗和正常绿苗的最大差异表现在叶绿体的结构上,而且这种差异在茎端细胞中就已明显地表现出来。白化细胞中没有发育正常的叶绿体,其质体的结构异常简单,主要含有一些小泡和嗜锇小球。白化苗质体的形态多呈不规则状,并且常常空化。随着叶片年龄的增长,白化质体的内容物逐渐变少,空泡化程度增大。然而,在这种发育不完善的质体中仍然有DNA状纤丝和核糖核蛋白体颗粒存在。说明白化苗质体仍具有基本的遗传和蛋白质合成机构。其发育的阻碍可能来自细胞核基因的突变。     

水稻花粉白苗的若干特性及其成因的探讨

水稻花粉白苗的再分化所生成的再生植株全为白苗,这说明花粉白苗的形成是不可逆的,可能是基因突变的结果。不同品种或杂交组合的水稻花粉白苗叶片丙酮提取液的吸收光谱相互间显示出了相似性,这种相似性就进而提示突变可能发生在基因组的特定位点上。有可能花粉白苗是质体DNA在花粉的脱分化过程中发生缺失形成的。这种缺失主要影响质体rRNA的合成水平,并不导致蛋白质和叶绿素合成能力的全面丧失。花粉植株细胞中的质体可能是不均一的。     

链霉菌原生质体的制备

原生质体是细胞去除了坚韧细胞壁后对渗透压极为敏感的球质体,最外层是裸露的细胞质膜,失去了细胞壁的原生质体,染色体ＤＮＡ在诱变剂作用下,更易引起死亡突变,敏感性提高。菌种的敏感性越高,诱发突变的机会越大。因此,用原生质体代替孢子、菌丝细胞作为诱变育种的...     

美日生物工程研究的几项成果

一、美国有两个公司的遗传工程组构建一种超分泌酵母突变株,该株是用去掉原凝乳酶(系非活性的)基因的质体(指杂种质体)引入酵母基因组内的,其凝乳酶的分泌效率提高10倍,最高达80倍(ASM News,51(11):560—56,1985)。     

Control of plastid division by means of nuclear DNA amount

Summary For a given cell type and genotype a close positive correlation exists between the number of plastids in a cell and the amount of DNA in the nucleus. Comprehensive evidence is presented. The duplication of the DNA amount entails an increase of the plastid number in differentiating cells by about 70%. Exceptions reported in the literature are critically examined. The odds are in favour of the assumption that exceptions to the rule which are not due to special circumstances do not exist. In meristematic cells even a duplication of the plastid number will occur, for cells without plastids are not to be found. The plastids are always ready to divide, the interpretation goes, but the size of their populations is limited by the amount of nuclear DNA. Thus meristematic cells manage to control their plastid populations by releasing once in a cell cycle the brakes imposed upon plastid division, whereupon the plastids make use of their newly won freedom, dividing until the old ratio between plastid number and nuclear DNA amount is established again. As a shorter time is needed for plastid division than for mitosis, there is no danger of cells arising without plastids; no distributing mechanism is required if at least three to four plastids are present in a cell. The findings are consistent with and would appear to be best explained by the theory of the symbiotic origin of the plastids.     

The history of research on white-green variegated plants

Plinius the Elder (23–79 A.D.) noted the existence of variegated varieties of ivy. But only subsequent to the middle of the last century, when botanists detected chloroplasts and began to study their origin, did variegation of leaves begin to be investigated scientifically. The white, yellow, or yellow-green parts of the many species of variegated leaves contain either leucoplasts, plastids in various stages of degeneration leading to their complete disappearance, or plastids containing only carotene or xanthophyll. In some cases normal and abnormal plastids are found together in “mixed” cells. In some cases the variegation is temperature and/or light sensitive.     

Occurrence of plastids in rye (Poaceae) sperm cells

Studies using classic genetics as well as restriction fragment length polymorphism analysis have demonstrated that rye, unlike most flowering plants, has biparental inheritance of both plastids and mitochondria. Yet, a previous in-depth ultrastructural study found no plastids in rye sperm cells, and DNA-specific staining revealed no cytoplasmic DNA in the male gametes of this plant. In the present study, we examined serial ultrathin sections of eight rye sperm cells (four pairs) and found unambiguous examples of plastids in all cases. The number of plastids per sperm cell varies from two to 12. The sperm of a pair may vary with regard to plastid number; however, these differences are not consistent among the sperm pairs examined.     

Mechanism of Protein Targeting to the Chlorarachniophyte Plastids and the Evolution of Complex Plastids with Four Membranes — A Hypothesis

Chlorarachniophyta are phototrophic amoeboflagellates, with plastids surrounded by four membranes. Contrary to other plastids of this type which occur in chromists, their outermost membrane bears no ribosomes. It is argued that the nuclear-encoded chlorarachniophyte plastid proteins are first transported into the ER, then to the Colgi apparatus, and finally to the plastids. The same import mechanism could be originally present in the chromist ancestor, prior to the fusion of their plastids with the RER membranes. According to the most recent concept, the complex plastids of Chromista and Chlorarachniophyta have evolved through replacement of the cyanobacterial plastids. The assumption that these plastids had an envelope composed not of two, but of three membranes makes it possible to avoid the erlier discerned difficulties with conversion of a eukaryotic alga into a complex plastid. My scenario provides an additional support to the hypothesis on polyphy-letic origin of four-membraned plastids.     

Phylogeny of Dinoflagellate Plastid Genes Recently Transferred to the Nucleus Supports a Common Ancestry with Red Algal Plastid Genes

It is generally accepted that peridinin-containing dinoflagellate plastids are derived from red alga, but whether they are secondary plastids equivalent to plastids of stramenopiles, haptophytes, or cryptophytes, or are tertiary plastids derived from one of the other secondary plastids, has not yet been completely resolved. As secondary plastids, plastid gene phylogeny should mirror that of nuclear genes, while incongruence in the two phylogenies should be anticipated if their origin was as tertiary plastids. We have analyzed the phylogeny of plastid-encoded genes from Lingulodinium as well as that of nuclear-encoded dinoflagellate homologues of plastid-encoded genes conserved in all other plastid genome sequences. Our analyses place the dinoflagellate, stramenopile, haptophyte, and cryptophyte plastids firmly in the red algal lineage, and in particular, the close relationship between stramenopile plastid genes and their dinoflagellate nuclear-encoded homologues is consistent with the hypothesis that red algal-type plastids have arisen only once in evolution.     

Plastid polarity and meiotic spindle development in microsporogenesis ofSelaginella

Summary Microsporogenesis inSelaginella was studied by fluorescence light microscopy and transmission electron microscopy. As in other examples of monoplastidic meiosis the plastids are involved in determination of division polarity and organization of microtubules. However, there are important differences: (1) the meiotic spindle develops from a unique prophase microtubule system associated with two plastids rather than from a typical quadripolar microtubule system associated with four plastids; (2) the division axes for first and second meiotic division are established sequentially, whereas as in all other cases the poles of second division are established before those of first division; and (3) the plastids remain in close contact with the nucleus throughout meiotic prophase and provide clues to the early determination of spindle orientation. In early prophase the single plastid divides in the plane of the future division and the two daughter plastids rotate apart until they lie on opposite sides of the nucleus. The procytokinetic plate (PCP) forms in association with the two slender plastids; it consists of two spindle-shaped microtubule arrays focused on the plastid tips with a plate of vesicles at the equatorial region and a picket row of microtubules around one side of the nucleus. Second plastid division occurs just before metaphase and the daughter plastids remain together at the spindle poles during first meiotic division. The meiotic spindle develops from merger of the component arrays of the PCP and additional microtubules emanating from the pair of plastid tips located at the poles. After inframeiotic interphase the plastids migrate to tetrahedral arrangement where they serve as poles of second division.Abbreviations AMS axial microtubule system - FITC fluorescein isothiocyanate - MTOC microtubule organizing center - PCP procytokinetic plate - QMS quadripolar microtubule system - TEM transmission electron microscope (microscopy)     

Plastid inheritance in the planktonic raphid pennate diatom Pseudo-nitzschia delicatissima (Bacillariophyceae)

Plastid inheritance was followed during sexual reproduction in the raphid pennate diatom Pseudo-nitzschia delicatissima, using rbcL haplotypes as plastid identification tools. Pseudo-nitzschia species are dioecious and show functional anisogamy with 'male' mating type+(PNd(+)) cells and 'female' PNd(-) cells. Vegetative cells possess two plastids. In P. delicatissima, meiosis results in two gametes that both contribute two plastids to the zygote. The latter initially contains four plastids, but during auxospore development two of these four seem to disappear, and the initial cell emerging from the auxospore appears to contain only two. Here we assessed if the plastids are inherited strictly unipaternally, strictly biparentally, or randomly. We traced the source of the plastids in the F(1) generation by using PNd(+) and PNd(-) parental strains with different rbcL genotypes, here denoted AA (homoplastidial, with two plastids of rbcL haplotype A) and BB (homoplastidial; two plastids of haplotype B). Results showed that 16 out of 96 strains raised each from single F(1) cells had retained two paternal (PNd(+)) plastids, 20 had two maternal (PNd(-)) plastids and the remaining 60 had one maternal and one paternal plastid. This pattern is in accordance with the hypothesis that either two of the four plastids are eliminated during auxospore formation, or that all plastids are retained in the auxospore and segregate in pairs joining at random during the first mitotic division of the initial cell. Heteroplastidic F(1)-strains retained the AB genotype throughout the vegetative phase of their life cycle. The finding that 60 out of 96 F(1) strains were heteroplastidial contrasts with an absence of such genotypes in our strains raised from single cells sampled in the Gulf of Naples.     

Genomes at the interface between bacteria and organelles

The topic of the transition of the genome of a free-living bacterial organism to that of an organelle is addressed by considering three cases. Two of these are relatively clear-cut as involving respectively organisms (cyanobacteria) and organelles (plastids). Cyanobacteria are usually free-living but some are involved in symbioses with a range of eukaryotes in which the cyanobacterial partner contributes photosynthesis, nitrogen fixation, or both of these. In several of these symbioses the cyanobacterium is vertically transmitted, and in a few instances, sufficient unsuccessful attempts have been made to culture the cyanobiont independently for the association to be considered obligate for the cyanobacterium. Plastids clearly had a cyanobacterial ancestor but cannot grow independently of the host eukaryote. Plastid genomes have at most 15% of the number of genes encoded by the cyanobacterium with the smallest number of genes; more genes than are retained in the plastid genome have been transferred to the eukaryote nuclear genome, while the rest of the cyanobacterial genes have been lost. Even the most cyanobacteria-like plastids, for example the "cyanelles" of glaucocystophyte algae, are functionally and genetically very similar to other plastids and give little help in indicating intermediates in the evolution of plastids. The third case considered is the vertically transmitted intracellular bacterial symbionts of insects where the symbiosis is usually obligate for both partners. The number of genes encoded by the genomes of these obligate symbionts is intermediate between that of organelles and that of free-living bacteria, and the genomes of the insect symbionts also show rapid rates of sequence evolution and AT (adenine, thymine) bias. Genetically and functionally, these insect symbionts show considerable similarity to organelles.     

Plastid inheritance in Job's tears,Coix lacryma-jobi L.

Summary The yellow striping in Job's tears showed nonchromosomal maternal inheritance of the trait producing green, yellow lethal and striped seedlings in the offspring in widely different ratios whenever the striped plant was used as female parent.Plastids in yellow regions of the striped plant were of various sizes and colours ranging from normal to minute size and light yellow or pale green to transparent ones. They were even absent in some cells. The plastids in the leaves of the yellow lethals were usually pale green.While the histological studies indicate the probability that the genetic determinants affecting plastids were in the cytoplasm, the possibility that all the abnormal plastid types could be different expressions of the same original mutation that occurred in the plastids, together with the extensive data on the breeding behaviour of the striped plant, is strongly in favour of the concepts of plastid mutation and autonomy.     

The Fine Structure of Plastids in Various Tissues in the Leaf Blade of Rice

Ultrastructural variations of plastids in a leaf blade of riceare examined by electron microscopy. Plastids are identifiedby their starch-accumulating activity in detached leaves illuminatedfor 48 h. Plastids are observed in all the tissues that containcytoplasm. The structure of plastids varies among differenttissues but is rather uniform within a tissue. Among varioustypes of plastids other than chloroplasts in chloren-chyma,plastids of guard cells, sieve elements, and companion cellsare characteristic of the respective tissues. Ultrastructuralfeatures of vascular bundles and stomata of the leaf blade ofrice are also described.