蕨类植物配子体育及其性器官分化的研究进展

作者概述了蕨类植物生活周期中不同发育阶段的特点,并着重介绍了不,植物生长调节物质,水和温度等因素对蕨类植物配子体发育的影响以及精子囊素,光,钙离子和其它植物生长调节物质在性器官形成和分化过程中的作用,同时作者对蕨类植物性器官分化的不稳定性进行了探讨,并结合目前蕨类植物性器官分化的遗传学和分子生物学研究的最新进展,说明蕨类植物作为研究系统在植物生物学研究领域中的优势。     

蕨类植物的配子体

蕨类植物的配子体杜桂森（首都师范大学生物系１０００３７）蕨类植物既是高等孢子植物,又是低等维管植物。就植物体的结构而言,它比苔藓植物进化,比裸子植物原始。蕨类植物的生活史为抱子体占优势的异型世代交替,有独立生活的孢子体和配子体。在配子体上分化形成精子...     

蕨类植物配子体发育及其性器官分化的研究进展

作者概述了蕨类植物生活周期中不同发育阶段的特点,并着重介绍了光、植物生长调节物质、水和温度等因素对蕨类植物配子体发育的影响以及成精子囊素、光、钙离子和其它植物生长调节物质在性器官形成和分化过程中的作用。同时作者对蕨类植物性器官分化的不稳定性进行了探讨、并结合目前蕨类植物性器官分化的遗传学和分子生物学研究的最新进展,说明蕨类植物作为研究系统在植物生物学研究领域中的优势。     

不同环境因子对珍稀观赏蕨类金毛狗配子体性别分化的影响

金毛狗[Cibotium barometz(L.)J.Sm.]是珍稀观赏蕨类的重要类群,为国家二级重点保护野生植物。该研究以金毛狗孢子为试验材料,探究培养密度、外源赤霉素以及光质等不同环境因子对金毛狗配子体性别分化的影响,为金毛狗人工繁育和蕨类植物配子体性别决定机制研究提供技术支持。结果表明:(1)低配子体培养密度(1个/cm2和5个/cm2)有利于颈卵器和雌配子体形成,随着配子体培养密度增加,颈卵器平均数量及雌配子体比率下降,精子器平均数量以及雄配子体和两性配子体比例增加,但配子体培养密度过高(80个/cm2)会导致大量无性配子体产生。(2)不同配子体培养密度下,随着培养时间延长,两性配子体比率均有增加,且增加幅度基本一致。(3)外源GA4显著抑制颈卵器和雌配子体形成,并显著促进精子器和雄配子体形成;外源GA3对金毛狗配子体性别分化没有显著影响。(4)白光、红光、蓝光等不同光质对金毛狗配子体性别分化未产生显著影响,但会影响配子体的发育和形态建成。     

环境因子对蕨类植物孢子萌发的影响

蕨类植物通过孢子萌发形成独立生活的配子体,配子体能够形成精子器和颈卵器,进而通过受精作用形成新的孢子体。孢子萌发是蕨类植物生活史过程中配子体世代向孢子体世代转变的关键步骤。同时,此过程不仅受到多种环境因子的影响,也是研究细胞核极性移动、细胞不对称分裂、假根极性生长等独特的细胞学事件的良好模型。迄今为止,人们已经研究发现多种环境因子对约200余种蕨类植物孢子萌发有影响。总结了环境因子对蕨类植物孢子萌发影响的规律如下:(1)孢子萌发除了受到光照强度影响外,主要受光质的影响,光质的影响主要表现为4种方式:①孢子萌发受红光刺激与远红光抑制像开关一样调控;②孢子萌发不受远红光抑制;③孢子萌发受蓝光抑制;④孢子只能在黑暗条件下萌发。(2)重力作用会影响孢子细胞核移动,进而影响孢子细胞发育的极性。(3)赤霉素(GA)能增加孢子萌发率或帮助孢子打破休眠。成精子囊素与GA作用相似,启动或促进孢子萌发。而脱落酸(ABA)、茉莉酸(JA)和乙烯等其它激素对孢子萌发的影响相对较小。(4)不同植物孢子有着各自最适的萌发培养基条件,如不同种类孢子对MS培养基中无机盐含量、蔗糖含量、pH值的要求不同。孢子外被中的Ca2+、Mn2+和Mg2+,培养基中的Cd2+和La3+,以及孢子接种密度、萌发空间CO2含量也会对孢子萌发造成影响。(5)多数蕨类植物孢子在15-30℃可以萌发,最适萌发温度为25℃。(6)4℃和液氮储藏可以延长孢子寿命并保持较高萌发率。     

揭开蕨类植物性别控制的奥秘

在维管植物中，蕨类植物是比较原始的类群，虽然它的高大的远古祖先如鳞木、芦木等埋在地底层中形成了煤，为现代的人类提供了重要的能源，但是现存的蕨类植物除桫椤外，都是草本植物。既没有象小麦、水稻那样重要的粮食作物，也没有其它一些对人类生活产生巨大影响的经济植物。也许正是因为过去它们较少的介入人类的生活，随着生活水平的提高，人们更喜爱蕨类植物的纯朴与自然。如今蕨类植物作为重要的观叶植物和具有独特风味的山野菜，正在逐渐走进人们的生活。蕨类植物与被子植物最显著的不同是在它的生长发育过程中没有花的形成，因此也…     

哺乳动物性别分化的调控

哺乳动物性别分化调控的分子机制的研究特别是性别分化的层次调控、剂量补偿和性染色体进化这三个领域,已取得快速进展。已经发现Ｙ染色体性别决定区基因（ＳＲＹ）、Ｘ染色体ＤＳＳ－ＡＨＣ决定区基因１（ＤＡＸ－１）、甾类生成因子１基因（ＳＦ１）和Ｗｉｌｍｓ瘤抑制基因（ＷＴ－１）等与哺乳动物性别决定有关。ＳＲＹ启动睾丸分化,但胚胎发育成雄性的其余步骤由睾丸分泌的激素控制。ＤＡＸ－１编码一种女性特异功能的蛋白质,     

芦笋性别决定与性别分化研究进展

从芦笋性别表现及其决定的遗传基础、性别分化途径,性别决定基因的定位以及性别分化特异表达基因的分离与分析等方面来综述芦笋性别决定与性别分化最新研究进展。目前,已构建了围绕芦笋性别决定基因M比较精细的遗传图谱,将M定位在L5染色体着丝点附近的0.63 cM区域内,并构建了含有8个跨叠克隆群的物理图谱,但由于大量重复序列的存在,跨叠克隆之间的空隙不能闭合;同时先后分离得到11个芦笋花器官发育特异表达基因,并通过序列分析和原位杂交等技术对这些基因的功能进行了分析。最后,对今后进一步研究提出了建议。     

线虫的性别分化和决定

线虫（Caeborhabditis elegans)是十分重要的模式生物。在遗传学,发育生物学以及神经生物学中有着广泛的应用。就线虫性别分化和性别决定相关基因的特性和功能进行了详细介绍,并在此基础上初步概括了其性别决定的分子机制。     

人类性别决定和性别分化研究进展

SRY基因在人类性别分化中起着关键作用,目前研究认为SRY仅是涉及性别决定过程的基因之一,其他基因和SRY相关基因SOX9,抗副中肾激素基因AMH,编码缁类因子的基因SF1,X－连锁的DAX基因,wilm‘s肿瘤抑制基因WT1等基因都参与了人类性腺分化和发育,本文拟就人类性别决定基因的研究进展及其与人类性别分化的关系作一综述。     

上海市蕨类植物分布特点及其与环境因子关系分析

在查阅资料和标本基础上,对上海市33个样地蕨类植物进行了野外调查,初步确定了上海市自然分布的蕨类植物23科31属50种,并讨论了归化种与栽培种及曾有记录而可能消亡的种类。采用双向指示种法（TWINSPAN）和典范对应分析（CCA）方法对蕨类植物分布特点及其与环境因子关系进行了分析。结果表明：（1）蕨类分布的样点可分为3组,第1组为市区样点,种数为0～4种;第2组为市郊样点,种数为0～8种;第3组为佘山岛、佘山地区、大金山岛,是上海蕨类最丰富地区,种数达26种以上。（2）影响上海蕨类植物生长的主要环境因子为基质、郁闭度和人为干扰。     

Biogeography of Mesozoic leptosporangiate ferns related to extant ferns

The paleobiogeography of the extant leptosporangiate fern families present in the Mesozoic is reviewed based mainly on data from megafossils that possess enough characters to be assigned to a family. Times of first appearances are discussed for each family, followed by their distribution throughout the Mesozoic. Paleolatitudes and climatic conditions indicate that first appearances of many fern families occur about or above 30° and in conditions of higher moisture. Much of fern distribution in the past was likely due to long-distance dispersal.     

Significance of gametophyte form in long-distance colonization by tropical, epiphytic ferns

Gametophyte morphology of tropical epiphytic ferns may confer an advantage for establishment on islands. Most tropical, epiphytic ferns belong to five families: Hymenophyllaceae, Grammitidaceae, Vittariaceae, Polypodiaceae, and Elaphoglossaceae. Gametophytes of these families are long-lived and clone-forming. In addition, most Hymenophyllaceae, Grammitidaceae, and Vittariaceae produce dispersible gemmae. Each of these characteristics increases opportunity for outbreeding, and when island floras are statistically compared with floras of adjacent mainlands, island floras are found to be rich in epiphytic species possessing gemmae (Hymenophyllaceae, Grammitidaceae, and Vittariaceae), and depauperate in epiphytic species lacking gemmae (Polypodiaceae and Elaphoglossaceae). We propose that gametophytic gemmae significantly aid long-distance colonization of outbreeding species because gemmae 1) allow gametophytes to exploit available niches through dispersal of gemmae, and through clonal expansion and persistence of the resulting gametophyte, and 2) facilitate sexual reproduction by providing the opportunity for sperm and antheridiogen transfer when gametophytes are distant, and by providing a new source of tissue for antheridia formation.     

Sex ratio variance and the maintenance of environmental sex determination

Although variation in population sex ratios is predicted to increase the extinction rate of clades with environmental sex determination (ESD), ESD is still seen in a wide array of natural systems. It is unclear how this common sex-determining system has persisted despite this inherent disadvantage associated with ESD. We use simulation modelling to examine the effect of the sex ratio variance caused by ESD on population colonization and establishment. We find that an accelerating function of establishment success on initial population sex ratio favours a system that produces variance in sex ratios over one that consistently produces even sex ratios. This sex ratio variance causes ESD to be favoured over genetic sex determination, even when the mean global sex ratio under both sex-determining systems is the same. Data from ESD populations suggest that the increase in population establishment can more than offset the increased risk of extinction associated with temporal fluctuations in the sex ratio. These findings demonstrate that selection in natural systems can favour increased variance in a trait, irrespective of the mean trait value. Our results indicate that sex ratio variation may provide an advantage to species with ESD, and may help explain the widespread existence of this sex-determining system.     

植物叶片最大羧化速率及其对环境因子响应的研究进展

植物叶片最大羧化速率对环境因子的响应关系是陆地生态系统生产力与碳收支研究的重要方面。论文从测定方法、影响因子与模拟模型3方面综述了植物叶片最大羧化速率及其对环境因子响应研究的最新进展,指出现有的植物叶片最大羧化速率对单个环境因子的响应研究严重制约着陆地生态系统生产力的准确评估。为弄清植物叶片最大羧化速率对环境因子的综合响应关系,迫切需要加强以下研究:(1)植物叶片最大羧化速率的生物与环境控制机制研究;(2)生物与环境因子协同作用下的植物叶片最大羧化速率定量模拟及其尺度化研究;(3)植物叶片最大羧化速率的环境因子阈值研究。     

Sex ratios in offspring of sex-reversed sea bass and the relationship between growth and phenotypic sex differentiation

Groups of sexually undifferentiated sea bass Dicentrarchus labrax were fed with the androgen 17α-methyltestosterone (MT) during sex differentiation. MT treatment increased males from 79±3% in the controls (the usual 3:1 male:female sex ratio of cultured sea bass) to 100±0%, implying that in the treated groups one out of each five resulting males was a masculinized female (neomale). Thirteen males from the MT treated groups were taken as the parental generation and their sperm used to individually fertilize a pool of eggs from unrelated females. The probability of having at least one neomale was 95% and most probably two or three of the males used were neomales. The offspring from each family were reared separately under the same environmental conditions. Samples were taken at 11 and 15 months of age, during and after sex differentiation, respectively. Results showed that females predominated among the larger fish whereas males and undifferentiated fish predominated among the smaller ones. Intersexes exhibited an intermediate size. All fish with a body length smaller than 12 cm were undifferentiated. These results suggest that sex differentiation is more dependent on length than on age. At 15 months, sex ratios were male-biased in all families, except one (females ranged from 5 to 50%) and only two families had sex ratios not significantly different from 1:1, suggesting that the mechanism of sex determination in the sea bass is not of a XX/XY or ZW/ZZ type since no family exhibited a female-biased progeny, as would be expected from both types. Results support the hypothesis that factors other than genetic, i.e., environmental, may act epigenetically on the sex determination mechanisms of sea bass, as has been demonstrated in other fishes.     

Sex allocation in aquatic ferns: The role of body size

Patterns of resource allocation reflect the plastic strategies that result from different selective pressures imposed by the environment. However, biomass allocation can be limited by architectural restrictions that change with the plant size. Our knowledge about sex allocation in heterosporous aquatic ferns remains scarce and studies on the reproductive strategies of these plants may yield valuable information regarding the evolutionary history of heterospory. Here, we investigate resources allocation, both in number and in biomass, to produce megasporangia and microsporangia among three species of Salvinia with different body sizes. Salvinia oblongifolia, S. auriculata and S. minima were collected in temporary ponds on the floodplain of the Pandeiros River in Brazil. We counted megasporangia and microsporangia, and measured their dry mass in each ramet. We also measured the total vegetative biomass and total reproductive biomass of each ramet in each species. Resource allocation to megasporangia production is associated with the specific body size of each species. However, the allocation for microsporangia production was higher in the species with intermediate size, which probably may be related to the drought event. The total reproductive biomass of each species was not dependent on the total vegetative biomass, but despite a similar reproductive effort, species differ on which sex is prioritized in the allocation process. Our results provide the first data about the processes underlying the sex allocation of Salvinia in the floodplains. The production of sori is size dependent in each Salvinia species and is shaped by drought, an intense selective pressure in temporary wet habitats.     

Sex determination and differentiation in organisms other than higher plants

The understanding of sex determination in general, but in particular in mammals, has been a subject of scientific speculation for a long time. It has been shown that in many vertebrate and invertebrate species, the sex of an individual is determined by the individual's chromosomal constitution. Initial studies of classical genetic searching for sex-transforming mutations and the scrupulous analyses of modified phenotypes have shed light on the mechanism(s) of sex-determination. They paved the road to successful studies at molecular level. After a brief review on sex determination in chosen model species, the “Drosophila system” is presented to exemplify a possible general principle for sex determinism.     

鱼类性别决定的影响因素

鱼类的性别决定机制极其复杂,受到外源性激素、外界环境因素和遗传因素等多方面的影响。因此,鱼类性别决定机制的研究不仅对我们控制鱼类的性别有帮助,也将使我们对脊椎动物性别决定的可塑性有一个全面的了解。该文对影响鱼类性别决定的各种因素及其研究前景和发展趋势进行综述。     

Temperature-Dependent Sex Determination in Sea Turtles in the Context of Climate Change: Uncovering the Adaptive Significance

The adaptive significance of temperature-dependent sex determination (TSD) in reptiles remains unknown decades after TSD was first identified in this group. Concurrently, there is growing concern about the effect that rising temperatures may have on species with TSD, potentially producing extremely biased sex ratios or offspring of only one sex. The current state-of the-art in TSD research on sea turtles is reviewed here and, against current paradigm, it is proposed that TSD provides an advantage under warming climates. By means of coadaptation between early survival and sex ratios, sea turtles are able to maintain populations. When offspring survival declines at high temperatures, the sex that increases future fecundity (females) is produced, increasing resilience to climate warming. TSD could have helped reptiles to survive mass extinctions in the past via this model. Flaws in research on sex determination in sea turtles are also identified and it is suggested that the development of new techniques will revolutionize the field.