莲科系统学和遗传多样性研究现状

分析回顾了莲科的系统位置、莲品种分类的现状与问题和莲的遗传多样性。莲科（Nelumbonaceae）植物传统上被归入睡莲科（Nymphaeaceae）。许多研究表明,莲科与睡莲科在形态、细胞、孢粉等方面差异很大,因而建立莲科,置于睡莲目（Nymphaeales）、毛茛目（Ranunculales）或莲目（Nelumbonales）中。分子系统学研究发现,睡莲科为被子植物的基部类群之一,而莲科则是真双子叶植物的基部类群之一,与山龙眼科和悬铃木科有密切关系。莲科含莲（Ndumbo nucifera）和美洲黄莲（N．lutea）两种,间断分布于太平洋的两岸。莲在我国有悠久的栽培历史和广大的栽培面积,栽培品种超过600个。由于杂交和反复回交的原因,品种之间的遗传关系非常复杂。莲的遗传资源的研究还很不充分,尤其是野生类型。对一些栽培品种的研究其实验材料又含有美洲黄莲的遗传组分,因而多高估了莲的遗传多样性。     

六角莲的解剖学研究

对六角莲的根,根茎,叶以及根和根茎的粉未进行了显微观察,为六角莲的鉴别提供了依据,此外,还对六角莲的理化鉴别进行了研究。     

莲瓣兰形态变异研究

莲瓣兰是分布于云南西北部、四川西南部和台湾的濒危兰花.本研究采用引种不同种群的莲瓣兰栽培在相同环境中的植株为实验材料,测定其形态性状并进行统计计算,分析莲瓣兰种群之间的形态变异以及亲缘关系.巢氏方差分析结果显示,莲瓣兰19个表型性状居群间方差百分比为22.162%,居群内方差百分比为77.838%,莲瓣兰形态变异主要来源于居群内;聚类分析显示保山施甸(SD),大理云龙形态(YL)较为接近,春剑贵州兴隆(XL)居群形态与莲瓣兰各居群差别较大,距离较远.研究结果可为莲瓣兰的类群划分、良种选育及野生资源的保护提供基础数据.     

莲藕染色体上荧光原位杂交方法的初探

用酶解滴片法制备莲的染色体标本片,在传统的荧光原位杂交(FISH)的方法上进行改进,得到了一种适合于莲的高效荧光原位杂交方法,为莲的分子细胞遗传学研究提供技术上的帮助。     

黄花倒水莲栽培及利用研究综述

黄花倒水莲(Polygala fallax Hemsl.)为远志科远志属灌木或小乔木,以根入药,有健脾利湿、活血调经的功能。为更好开发利用黄花倒水莲资源,综述了其生物学特性、栽培与育种、组培快繁、化学成分和药理作用以及提取工艺等方面研究,并对黄花倒水莲丰产开发技术的研究方向作出展望。     

莲藕染色体上荧光原位杂交方法的初探

用酶解滴片法制备莲的染色体标本片,在传统的荧光原位杂交(FISH)的方法上进行改进,得到了一种适合于莲的高效荧光原位杂交方法,为莲的分子细胞遗传学研究提供技术上的帮助。     

保安湖莲群丛分布格局分形特征的初步研究

应用非线性科学中的分形几何理论,以保安湖扁担塘湖汊中的莲群丛为对象,研究该群丛小尺度水平格局的分形特征。主要应用计盒维数和信息维数公式计算群丛中莲种群和菱种群的个体分布格局的分维值,莲的计盒维数为1.92,信息维数为1.88;菱的计盒维数为1.04,信息维数为1.11.表明在采样区莲的空间占有程度远大于菱,是该时期的优势种,而菱则成为伴生种。莲在各尺度上的分布较均匀。最后讨论了莲的分维值在连续样方上的变化。       

莲胚愈伤组织诱导及植株再生的研究

关于莲胚组织培养国内外有过研究,但迄今利用组织培养技术从莲胚诱导愈伤组织形成再生植株的成功例子尚未见有报道。     

莲的生物活性成分及生理功能研究进展

莲（Nelumbo nucifera Gaertn.）是莲科莲属（Nelumbo）的多年水生双子叶草本植物,在中国湖北、江苏、安徽、江西、湖南、浙江等地区大量种植。研究表明,莲不同部位含有大量生物活性成分,包括多酚类、生物碱、多糖类、膳食纤维、维生素、氨基酸及多种微量元素。从莲中提取的生物活性成分具有多种生理功能,如抗炎、抗氧化、抗衰老、抗肿瘤、降血糖、降血脂、减肥、护肝、护肾、促进睡眠、免疫调节、治疗阿尔茨海默病、抗病毒、缓解抑郁症等。综述了近年来国内外对莲不同部位的生物活性成分以及其生理功能的最新研究进展,旨在为深入挖掘莲药用价值提供理论参考。     

莲子长寿机制的研究进展

莲( Nelumbo nucifera Gaertn.)为莲科、莲属多年水生宿根草本植物。莲子生命力极强,在自然条件下的泥碳层中能存活千年,甚至在极端高温、高湿条件下仍能保持较高的萌发活力。随着莲基因组测序与基因注释的完善,莲子长寿机制的相关研究取得了一定进展。本文对莲子的结构形态、保护系统和基因组特性方面的研究进展进行了综述,阐明莲子的长寿机制,对后续研究方向进行了展望。     

Kinetochore individualization in meiosis I is required for centromeric cohesin removal in meiosis II

Partitioning of the genome in meiosis occurs through two highly specialized cell divisions, named meiosis I and meiosis II. Step‐wise cohesin removal is required for chromosome segregation in meiosis I, and sister chromatid segregation in meiosis II. In meiosis I, mono‐oriented sister kinetochores appear as fused together when examined by high‐resolution confocal microscopy, whereas they are clearly separated in meiosis II, when attachments are bipolar. It has been proposed that bipolar tension applied by the spindle is responsible for the physical separation of sister kinetochores, removal of cohesin protection, and chromatid separation in meiosis II. We show here that this is not the case, and initial separation of sister kinetochores occurs already in anaphase I independently of bipolar spindle forces applied on sister kinetochores, in mouse oocytes. This kinetochore individualization depends on separase cleavage activity. Crucially, without kinetochore individualization in meiosis I, bivalents when present in meiosis II oocytes separate into chromosomes and not sister chromatids. This shows that whether centromeric cohesin is removed or not is determined by the kinetochore structure prior to meiosis II.     

Loss of complementation and the logic of two-step meiosis

Meiosis is usually a two-step process: two divisions preceded by a duplication. One-step meiosis, a single division without prior replication, is a more logical way to produce haploid gametes; moreover, one-step meiosis leads to higher variabilty in the progeny than two-step meiosis. Yet one-step meiosis is very rare in nature, and may not even exist at all. I suggest that this is because one-step meiosis, in contrast to two-step meiosis, can be easily invaded and replaced by asexual reproduction. I discuss why other existing peculiar forms of division leading to the production of haploid gametes, but not one-step meiosis, have the same effect as two-step meiosis.     

The reduction of chromosome number in meiosis is determined by properties built into the chromosomes

In meiosis I, two chromatids move to each spindle pole. Then, in meiosis II, the two are distributed, one to each future gamete. This requires that meiosis I chromosomes attach to the spindle differently than meiosis II chromosomes and that they regulate chromosome cohesion differently. We investigated whether the information that dictates the division type of the chromosome comes from the whole cell, the spindle, or the chromosome itself. Also, we determined when chromosomes can switch from meiosis I behavior to meiosis II behavior. We used a micromanipulation needle to fuse grasshopper spermatocytes in meiosis I to spermatocytes in meiosis II, and to move chromosomes from one spindle to the other. Chromosomes placed on spindles of a different meiotic division always behaved as they would have on their native spindle; e.g., a meiosis I chromosome attached to a meiosis II spindle in its normal fashion and sister chromatids moved together to the same spindle pole. We also showed that meiosis I chromosomes become competent meiosis II chromosomes in anaphase of meiosis I, but not before. The patterns for attachment to the spindle and regulation of cohesion are built into the chromosome itself. These results suggest that regulation of chromosome cohesion may be linked to differences in the arrangement of kinetochores in the two meiotic divisions.     

Inverted meiosis and the evolution of sex by loss of complementation

Inverted meiosis, in which sister chromatids segregate before homologous chromosomes, is a common aberration of conventional meiosis (in which sister chromatids segregate after homologous chromosomes) and is routinely observed in certain species. This raises an evolutionary mystery: what is the adaptive advantage of the more common, conventional order of segregation in meiosis? I use a population genetic model to show that asexual mutants arising from inverted meiosis are relatively immune from the deleterious effects of loss of complementation (heterozygosity), unlike the asexual mutants arising from conventional meiosis, in which loss of complementation can outweigh the two‐fold cost of meiosis. Hence, asexual reproduction can replace sexual reproduction with inverted meiosis, but not with conventional meiosis. The results are in line with analogous considerations on other alternative types of reproduction and support the idea that amphimixis is stable in spite of the two‐fold cost of meiosis because loss of complementation in mutant asexuals outweigh the two‐fold cost.     

Effect of cumulus and granulosa cells on meiosis resumption in murine oocytes in vitro

Effects of different follicular cell types on resumption of meiosis were studied. Cumulus enclosed oocytes (CEO), denuded oocytes (DO), cumulus cells (CCs) and mural granulosa cells (GCs) were used. Oocytes were obtained from mature gonadotrophin-stimulated and unstimulated mice. The resumption of meiosis was assessed by the germinal vesicle breakdown (GVBD) at the end of cultivation. It has been shown that GCs produced a meiosis activating substance due to gonadotrophin stimulation; for meiosis resumption connections between CCs and the oocyte were not necessary, but the very production of the meiosis activating substance, was, however, dependent on the initial connection between CCs and the oocyte. The presence of oocyte was necessary for stimulating CCs to produce a diffusible heat stable meiosis activating substance; gonadotrophins induced CCs to produce a diffusible thermostable meiosis activating substance. This substance induced, in a paracrine fashion, resumption of meiosis directly. It is proposed that the heat stable meiosis activating component of the used media from gonadotrophins-stimulated CEO may belong to a kind of meiosis activating sterols, previously isolated from human follicular fluid and from adult bull testes.     

The role of shugoshin in meiotic chromosome segregation

During meiosis, DNA replication is followed by 2 successive chromosome segregation events, resulting in the production of gametes with a haploid number of chromosomes from a diploid precursor cell. Faithful chromosome segregation in meiosis requires that sister chromatid cohesion is lost from chromosome arms during meiosis I, but retained at centromeric regions until meiosis II. Recent studies have begun to uncover the mechanisms underlying this stepwise loss of cohesion in meiosis and the role of a conserved protein, shugoshin, in regulating this process.     

Ime2p and Cdc28p: co-pilots driving meiotic development

Meiosis can be considered an elaboration of the cell division cycle in the sense that meiosis combines cell-cycle processes with programs specific to meiosis. Each phase of the cell division cycle is driven forward by cell-cycle kinases (Cdk) and coordinated with other phases of the cycle through checkpoint functions. Meiotic differentiation is also controlled by these two types of regulation; however, recent study in the budding yeast S. cerevisiae indicates that progression of meiosis is also controlled by a master regulator specific to meiosis, namely the Ime2p kinase. Below, I describe the overlapping roles of Ime2p and Cdk during meiosis in yeast and speculate on how these two kinases cooperate to drive the progression of meiosis.     

Sgo1 is required for co-segregation of sister chromatids during achiasmate meiosis I

The reduction of chromosome number during meiosis is achieved by two successive rounds of chromosome segregation, called meiosis I and meiosis II. While meiosis II is similar to mitosis in that sister kinetochores are bi-oriented and segregate to opposite poles, recombined homologous chromosomes segregate during the first meiotic division. Formation of chiasmata, mono-orientation of sister kinetochores and protection of centromeric cohesion are three major features of meiosis I chromosomes which ensure the reductional nature of chromosome segregation. Here we show that sister chromatids frequently segregate to opposite poles during meiosis I in fission yeast cells that lack both chiasmata and the protector of centromeric cohesion Sgo1. Our data are consistent with the notion that sister kinetochores are frequently bi-oriented in the absence of chiasmata and that Sgo1 prevents equational segregation of sister chromatids during achiasmate meiosis I.Key words: meiosis, chromosome segregation, recombination, kinetochore, Sgo1, fission yeast     

细胞骨架与卵子减数分裂器的再启动和旋转关系的研究

本文采用体外授精(IVF)技术,通过小鼠受精卵早期发育过程中的形态变化,来研究受精过程中减数分裂器的重新启动与旋转。得到以下几个结果:①精子是在小鼠卵子的减数分裂器旋转之前进入卵子,随后精核发生去凝缩,从而使停滞的减数分裂器复苏启动。②雄性原核的形成过程,伴随着减数分裂器的旋转过程,雄性原核的形成要比雌性原核的为早。③在减数分裂器旋转过程中,微丝不仅参与,并且控制着旋转;解聚微丝,将阻止减数分裂器的旋转。④微管是减数分裂器的主要构成部分,它的稳定为减数分裂器形成提供了保证;解聚微管,将使减数分裂器解体。     

Separate effects of triploidy, parentage and genomic diversity upon feeding behaviour, metabolic efficiency and net energy balance in the Pacific oyster Crassostrea gigas

Triploid oysters were induced using cytochalasin B upon retention of either the first (meiosis I triploids) or the second (meiosis II triploids) polar body in embryos from a single cohort derived from mixed parentage. Allozyme and microsatellite assays enabled the confirmation of both parentage and triploidy status in each oyster. Comparison of meiosis I triploids, meiosis II triploids and diploid siblings established that improved physiological performance in triploids was associated with increased allelic variation, rather than with the quantitative dosage effects of ploidy status. An unidentified maternal influence also interacted with genotype. Among full sibs, allelic variation measured as multi-locus enzyme heterozygosity accounted for up to 42% of the variance in physiological performance; significant positive influences were identified upon feeding rate, absorption efficiency, net energy balance and growth efficiency (= net energy balance divided by energy absorbed). Whilst allelic variation was greater in both meiosis I and meiosis II triploids than in diploid siblings, both allelic variation and net energy balance were highest in triploids induced at meiosis I. This suggests that it may be preferable to induce triploidy by blocking meiosis I, rather than meiosis II as has traditionally been undertaken during commercial breeding programmes.