细胞质遗传并非都是母系遗传

细胞质遗传一般表现为具母系遗传的特征。随着ＤＮＡ分子标记技术的发展和应用,人们已发现在动物及植物中均存在有低频的线粒体ＤＮＡ单亲父系遗传及双亲遗传的现象,对质体ＤＮＡ遗传的研究表明,被子植物的质体ＤＮＡ大多表现为母系遗传。而裸子植物的质体ＤＮＡ则主要表现为父系遗传的方式,同时也出现存在其它的遗传规律。     

打碗花生殖细胞,精细胞及卵细胞中的细胞质类核

已有不少超微结构的资料阐明被子植物双亲和单亲母系质体遗传的细胞学基础。近年应用DAPI荧光染色的方法,可快速地从检测质体DNA存在的状况确定被子植物中具双亲遗传潜能的种。从质体的类核存在与否判断质体遗传方式为母系遗传或双亲遗传与已有的遗传分析结论基本一致,只有少数种类是矛盾的。DAPI荧光技术可以认为是研究细胞质遗传机理的一个重要手段。我们曾证明旋花科牵牛属植物生殖细胞、精细胞中存在细胞质类核,确定其具双亲或单亲父系质体遗传的潜能,并用RFLP技术进一步确定其为质体父系遗传型。本研究证明旋花科的打碗花属生殖细胞、精细胞和卵细胞中细胞质类核存在的状况与牵牛属的相似,提供了打碗花可能在质体遗传上与牵牛属 具相同的遗传方式的资料。     

王百合及兰州百合细胞质遗传的细胞学研究

描述了王百合（ＬｉｌｉｕｍｒｅｇａｌｅＷｉｌｓ．）及兰州百合（Ｌ．ｄａｖｉｄｉＤｕｃｈ．）质体和线粒体在生殖细胞及精细胞中的分布和细胞质中ＤＮＡ的状况。在刚形成的王百合的生殖细胞中含有少量的质体和大量的线粒体。当生殖细胞游离在营养细胞质中时,质体在生殖细胞中完全退化消失。ＤＡＰＩ荧光技术进一步证明,在成熟花粉、花粉管中的生殖细胞及其分裂形成的两个精细胞中无任何细胞器ＤＮＡ。兰州百合在小孢子分裂时质体严格地极性分布,造成了刚形成的生殖细胞中即无质体。兰州百合、麝香百合（Ｌ．ｌｏｎｇｉｆｌｏｒｕｍＴｈｕｎｂ．）及其杂种的ＲＦＬＰ分析,也证明兰州百合质体是单亲母系传递的。虽然在不同发育时期的生殖细胞及精细胞中可以观察到线粒体,但在雄配子体时期它们的ＤＮＡ已降解,因此雄性线粒体不能被传递至后代。研究结果提供了百合属的这两个种质体和线粒体具母系遗传方式的细胞学证据,并阐明父系细胞质不能作为遗传传递的机理。     

菜豆花粉发育中质体和线粒体及其DNA存在的状况——着重阐明质体遗传…

应用电镜和ＤＮＡ的ＤＡＰＩ荧光检测技术研究了菜豆小孢子／花粉发育中质体和线粒体及其ＤＮＡ存在的状况。观察表明：在小孢子分裂时质体全部分配到营养细胞中，初形成的生殖细胞已不含质体。线粒体和质体的ＤＮＡ在花粉发育中也先后降解，生殖细胞从刚形成时发育至成熟花粉时期这两种细胞器ＤＮＡ均不存在。研究结果为菜豆质体母系遗传提供了确切的细胞学证据。遗传分析的研究曾确定菜豆质体为双亲遗传，与对本研究结论不同的原因     

菜豆花粉发育中质体和线粒体及其DNA存在的状况——着重阐明质体遗传的细胞学基础

应用电镜和DNA的DAPI荧光检测技术研究了菜豆(Phaseolus vulgaris L.)小孢子/花粉发育中质体和线粒体及其DNA存在的状况。观察表明:在小孢子分裂时质体全部分配到营养细胞中,初形成的生殖细胞已不含质体。线粒体和质体的DNA在花粉发育中也先后降解,生殖细胞从刚形成时发育至成熟花粉时期这两种细胞器DNA均不存在。研究结果为菜豆质体母系遗传提供了确切的细胞学证据。遗传分析的研究曾确定菜豆质体为双亲遗传,对与本研究结论不同的原因进行了讨论。     

油松细胞质遗传的细胞学机理:Ⅱ.雄性和雌性细胞器在受精和原胚时期的传递(英文)

在电镜下观察油松 (PinustabulaeformisCarr.)传粉后的胚珠临近受精时的花粉管和卵细胞的细胞质、受精时雄配子体细胞质的传递、游离核和细胞原胚发育时期质体和线粒体的传递。在成熟卵细胞中含许多线粒体 ,缺少正常结构的质体 ,它们转变为大内含体。此外 ,卵细胞还有丰富的小内含体和其他一些细胞器。花粉管在卵细胞的珠孔端释放其内含物。精核与卵核融合时 ,核周围未见来自精细胞的质体和线粒体。不参与融合的精核停留在接受液泡旁 ,在其周围有大量的雄性细胞质 ,其中混合有精细胞、管细胞和卵细胞的细胞器。在游离核原胚时期 ,核周区的细胞质中可见雄性与雌性亲本的细胞器相混合 ;其中许多线粒体与原来卵细胞中的线粒体有相同的形态 ,也有一些线粒体看来是来自精细胞和管细胞 ;质体是由雄配子体传递 ,形态与精细胞的或花粉管中的质体相似。卵细胞中变异的质体 (即大内含体 )在原胚发育时期变为液泡状 ,而雄性质体参加到新细胞质中。在原胚细胞中 ,线粒体大多数为母本来源 ,质体则表现为精细胞或管细胞的质体形态。该研究确定了油松具父系质体和双亲线粒体遗传的细胞学基础。对裸子植物线粒体和质体遗传的机理从细胞学的角度进行了分析。     

豌豆生殖细胞的发育—着重论述质体母系遗传的细胞学基础

超微结构的研究证明,豌豆（Ｐｉｓｕｍ ｓａｔｉｖｕｍ Ｌ．）生殖细胞自形成直至成熟花粉时期,始终存在少量质体和较多的线粒体。ＤＮＡ 荧光的观察表明,在发育早期的生殖细胞中不含细胞质ＤＮＡ 类核,但在成熟花粉的生殖细胞中有许多的类核。在花粉离体萌发过程中,随着花粉管的生长,生殖细胞中的类核逐渐降解。在花粉培养２４ ｈ 后,生殖细胞的类核全部消失。研究结果确定了豌豆质体母系遗传的细胞学基础,支持遗传分析及ＲＦＬＰ研究的结论,阐明了过去在细胞学上认为是双亲遗传的判断不正确的原因     

甘薯质体遗传方式的DNA指纹图谱分析

用DNA指纹图谱分析了甘薯(Ipomoea batatas Lam.)徐薯18和AB78-1品系及它们的正反交子代叶绿体DNA,结果显示子代叶绿体DNA指纹均与母本相同,而未发现与父本或双亲相同的指纹图谱,因此在该杂交组合中质体遗传方式为母系遗传.这个结论与先前根据细胞学研究所推测的甘薯质体遗传方式不同,表明旋花科植物可能并不存在一个一致的父系或双亲质体传递模式.DNA指纹图谱分析用于质体遗传的研究尚未见报道,本文对其优越性进行了讨论.     

甘薯质体遗传方式的DNA指纹图谱分析

用DNA指纹图谱分析了甘薯（Ipomoea batatasLam.)徐薯18和AB78-1品系及它们的正反交子代叶绿体DNA,结果显示子代叶绿体DNA指纹均与母本相同,而未发现与父本或双亲相同的指纹图谱,因此在该杂交组合中质体遗传方式为母系遗传,这个结论与先前根据细胞学研究所推测的甘薯质体遗传试不同。表明旋花科植物可能并不存在一个一致的父系或双亲质体传递模式。DNA指纹图谱分析用于质体遗传的研究尚未见报道,本文对其优越性进行了讨论。     

牵牛属质体DNA的父系遗传

利用限制性片段长度多态性（ＲＦＬＰ）技术研究了牵牛属（Ｐｈａｒｂｉｔｉｓ）植物质体ＤＮＡ 的遗传方式。结果表明,在牵牛（Ｐ． ｎｉｌ）×大花牵牛（Ｐ． ｌｉｍｂａｔａ）和大花牵牛×牵牛中,质体ＤＮＡ 为父系遗传。在大花牵牛×牵牛中,质体ＤＮＡ还有可能为双亲遗传。研究证明牵牛属为被子植物中具有质体父系遗传方式的第三个属。牵牛属质体父系遗传机制尚不清楚,作者认为母系质体及其ＤＮＡ 在受精后的释稀、排除和／或降解可能是质体父系遗传的基础     

Cytological Basis of Plastid Inheritance in Phaseolus vulgaris-Investigations of Plastids,Mitochondria and Their DNA Nucleoids During Pollen Development

Electron microscopic and DNA fluorescence microscopic observations of the plastids, mitochondria and their DNA in the developing pollen of Phaseolus vulgaris L. have demonstrated that the male plastids were excluded during microspore mitosis. The formed generative cell was free of plastids because of regional localization of plastids in early developing microspore and the extremely unequal distribution during division. The fluorescence observations of DNA showed that cytoplasmic (plastid and mitochondria) nucleoids degenerated and disappeared during the development of microspore/pollen, and were never presented in the generative cell at different development stages. These results provided precise cytological evidence of maternal plastid inheritance in Phaseolus vulgaris, which was not in accord with the biparental plastid inheritance identified from early genetic analysis. Based on authors' previous observations in a variety of common bean that the organelle DNA of male gamete was completely degenerated, the early genetic finding of the biparental plastid inheritance was unlikely to be effected by genotypic difference. Thus those biparental plastid inheritance might be caused by occational male plastid transmission, and plastid uniparental maternal inheritance was the species character of Phaseolus vulgaris.     

The model plant Medicago truncatula exhibits biparental plastid inheritance

The plastid, which originated from the endosymbiosis of a cyanobacterium, contains its own plastid DNA (ptDNA) that exhibits a unique mode of inheritance. Approximately 80% of angiosperms show maternal inheritance, whereas the remainder exhibit biparental inheritance of ptDNA. Here we studied ptDNA inheritance in the model legume, Medicago truncatula. Cytological analysis of mature pollen with DNA-specific fluorescent dyes suggested that M. truncatula is one of the few model plants potentially showing biparental inheritance of ptDNA. We further examined pollen by electron microscopy and revealed that the generative cell (a mother of sperm cells) indeed has many DNA-containing plastids. To confirm biparental inheritance genetically, we crossed two ecotypes (Jemalong A17 and A20), and the transmission mode of ptDNA was investigated by a PCR-assisted polymorphism. Consistent with the cytological observations, the majority of F(1) plants possessed ptDNAs from both parents. Interestingly, cotyledons of F(1) plants tended to retain a biparental ptDNA population, while later emergent leaves tended to be uniparental with either one of the parental plastid genotypes. Biparental transmission was obvious in the F(2) population, in which all plants showed homoplasmy with either a paternal or a maternal plastid genotype. Collectively, these data demonstrated that M. truncatula is biparental for ptDNA transmission and thus can be an excellent model to study plastid genetics in angiosperms.     

Heterogeneous pollen in Chlorophytum comosum, a species with a unique mode of plastid inheritance intermediate between the maternal and biparental modes

The majority of angiosperms display maternal plastid inheritance. The cytological mechanisms of this mode of inheritance have been well studied, but little is known about its genetic relationship to biparental inheritance. The angiosperm Chlorophytum comosum is unusual in that different pollen grains show traits of different modes of plastid inheritance. About 50% of these pollen grains exhibit the potential for biparental plastid inheritance, whereas the rest exhibit maternal plastid inheritance. There is no morphological difference between these two types of pollen. Pollen grains from different individuals of C. comosum all exhibited this variability. Closer examination revealed that plastid polarization occurs, with plastids being excluded from the generative cell during the first pollen mitosis. However, the exclusion is incomplete in 50% of the pollen grains, and the few plastids distributed to the generative cells divide actively after mitosis. Immunoelectron microscopy using an anti-DNA antibody demonstrated that the plastids contain a large amount of DNA. As there is a considerable discrepancy between the exclusion and duplication of plastids, resulting in plastids with opposite fates occurring simultaneously in C. comosum, we propose that the species is a transitional type with a mode of plastid inheritance that is genetically intermediate between the maternal and biparental modes.     

Cytological Studies of the Cytoplasmic Inheritance in Lilium regale and L. davidii

The distribution and characteristics of plastids and mitochondria in the generative and sperm cells of Lilium regale Wils. and L. davidii Duch. were described. In L. regale there were few plastids and abundant mitochondria in the newly formed generative cell. When the generative cell became free in the vegetative cytoplasm, the plastids degenerated completely within the generative cell. It was further proved by DAPI fluorescent technique that there was no organell DNA in the generative cell within the mature pollen grain or the pollen tube. However, distribution of the plastids was strictly polarizable during the division of the micmspore in L. davidii, resulting the lack of plastids in the newly formed generative cell. Data of RFLP analysis comparable between L. davidii, L. longifiorum and their interspecific hybrid have also proved the plastid inheritance in L. davidii to be of uniparental maternal transmission. Although the mitoehondria were observed both in the generative and sperm cells of L. regale and L. davidii but their DNA was decomposed in the male gametophyte stage. Therefore the mitochondda in the sperm cell could not be transmitted into the offspring. The results provided the detail, cytological evidence that organelles in the microgametophyte are incapable of genetic transmission in the two species of Lilium.     

Populations of plastids and mitochondria during male reproductive cell maturation in Nicotiana tabacum L.: A cytological basis for occasional biparental inheritance

The dynamics of plastid and mitochondrial populations in male reproductive cells of tobacco (Nicotiana tabacum L.) were examined during development using serial ultrathin sections and transmission electron microscopy to reconstruct 58 generative cells and 31 sperm cells at selected stages of maturation from generative cell formation through gametic fusion. The first haploid mitosis resulted in incomplete exclusion of plastids providing an average of 2.81 plastids and 82.7 mitochondria for each newly formed generative cell. During generative-cell maturation, plastid content decreased to an average of 0.48 plastids/generative cell at anthesis owing to autophagy of organelles. Plastids were present in low frequency within generative and sperm cells in the pollen tube and appeared to be transmitted, according to observations immediately prior to fertilization. This forms a cytological basis for genetic reports of occasional biparental plastid inheritance. In contrast, mitochondria were transmitted in larger numbers, and approximately 80 mitochondria per generative cell or sperm cell pair were retained throughout development. This provides a potentially stable source for the transmission of male mitochondrial DNA, if present at fertilization.Abbreviations GC generative cell - SC sperm cell We thank Dr. Frank J. Sonleitner, for helpful suggestions on the statistical calculations and Dr. Bing-Quan Huang for technical assistance in the preparation of embryo sacs during fertilization. This research was supported in part by U.S. Department of Agriculture grant 91-37304-6471. We gratefully acknowledge use of the Samuel Roberts Noble Electron Microscopy Laboratory of the University of Oklahoma.     

Mechanisms for independent cytoplasmic inheritance of mitochondria and plastids in angiosperms

The inheritance of mitochondria and plastids in angiosperms has been categorized into three modes: maternal, biparental and paternal. Many mechanisms have been proposed for maternal inheritance, including: (1) physical exclusion of the organelle itself during pollen mitosis I (PMI); (2) elimination of the organelle by formation of enucleated cytoplasmic bodies (ECB); (3) autophagic degradation of organelles during male gametophyte development; (4) digestion of the organelle after fertilization; and (5)—the most likely possibility—digestion of organellar DNA in generative cells just after PMI. In detailed cytological observations, the presence or absence of mitochondrial and plastid DNA in generative cells corresponds to biparental/paternal inheritance or maternal inheritance of the respective organelle examined genetically. These improved cytological observations demonstrate that the replication or digestion of organellar DNA in young generative cells just after PMI is a critical point determining the mode of cytoplasmic inheritance. This review describes the independent control mechanisms in mitochondria and plastids that lead to differences in cytoplasmic inheritance in angiosperms.     

Cytoplasmic Inheritance of Sweet Potato: with Respect to the Study of Plastids and Mitochondria and the Existence of Their DNA in Sperm Cells

The mature pollen of sweet potato ( Ipomoea batatas lam. ) was bicellular. After pollination generative cell divided into a pair of sperm cells before its germination. The pair of sperm cells remained in the hydrated pollen was similar in their shape and volume with enriched cytoplasmic plastids and mitochondria. The specific fluorescence of cytoplasm DNA indicated that the sperm cells and the generative cell contained numerous organelle nucleoids. The pair of sperm cells had no significant difference in their numbers of organelle nucleoids. Two kinds of organelle nucleoids existed in the pair of sperm cells. Tile ones as big and strong fluorescent dots appeared to be the plastid nucleoids and the others as tile small and weak fluorescent dots could be the mitochondrial nucleoid. Few of the angiosperms were of biparental or paternal plastid inheritance. The result of this study has provided the cytological evidence for another genus, Ipomoea, which is of biparental or paternal plastid inheritance besides Pharbitis and Calystegia in Convolvulaceae.     

Occurrence of plastids in the sperm cells of Caprifoliaceae: biparental plastid inheritance in angiosperms is unilaterally derived from maternal inheritance

It is widely held that organelles inherit from the maternal lineage. However, the plastid genome in quite a few angiosperms appears to be biparentally transmitted. It is unclear how and why biparental inheritance of the genome became activated. Here, we detected widespread occurrence of plastids in the sperm cells (a cellular prerequisite for biparental inheritance) of traditional Caprifoliaceae. Of the 12 genera sampled, the sperm cells of Abelia, Dipelta, Heptacodium, Kolkwitzia, Leycesteria, Linnaea, Lonicera, Symphoricarpos, Triosteum and Weigela possessed inheritable plastids. The other genera, Sambucus and Viburnum, lacked plastids in sperm cells. Interestingly, such exclusion of plastids in the sperm cells of some Caprifoliaceae appeared to be associated with the divergence of Dipsacales phylogeny. Closer examination of Weigela florida revealed that both plastids and plastid DNA were highly duplicated in the generative cells. This implies that the appearance of plastids in sperm cells involved cellular mechanisms. Because such mechanisms must enhance the strength of plastid transmission through the paternal lineage and appear ubiquitous in species exhibiting biparental or potential biparental plastid inheritance, we presume that biparental plastid genetics may be a derived trait in angiosperms. This is consistent with our extended phylogenetic analysis using species with recently discovered modes of potential plastid inheritance. The results show that basal and early angiosperms have maternal plastid transmission, whereas all potential biparental transmission occurs at terminal branches of the tree. Thus, unlike previous studies, we suggest that biparental plastid inheritance in angiosperms was unilaterally converted from the maternal transmission mode during late angiosperm evolution.     

玉竹雄配子的发育——着重阐明质体在生殖细胞和营养细胞中的分布和变化

玉竹(Polygonatum simizui Kitag)小孢子在分裂前,质体极性分布导致分裂后形成的生殖细胞不含质体,而营养细胞包含了小孢子中全部的质体。生殖细胞发育至成熟花粉时期,及在花粉管中分裂形成的两个精细胞中始终不含质体。虽然生殖细胞和精细胞中都存在线粒体,但细胞质中无DNA类核。玉竹雄性质体的遗传为单亲母本型。在雄配子体发育过程中,营养细胞中的质体发生明显的变化。在早期的营养细胞质中,造粉质体增殖和活跃地合成淀粉。后期,脂体增加而造粉质体消失。接近成熟时花粉富含油滴。对百合科的不同属植物质体被排除的机理及花粉中贮藏的淀粉与脂体的转变进行了讨论。