林木多倍体诱导研究的历史与现状

本文综述了林木多倍体诱导研究领域的历史与现状 在Dustin等人发现了秋水仙素在多倍体诱导上的巨大作用以后的 60多年中 ,研究人员运用秋水仙素处理诱导的方法获得了大量的植物人工多倍体 ,其中有一部分已被成功的用于农作物的育种与改良 在林木的人工多倍体中 ,阔叶树的多倍体表现要好于针叶树 ,它们经常表现出比其二倍体原种更好的生长特性和木材品质 随着多倍体诱导技术的日益成熟 ,多倍体育种将在林木改良领域展现出越来越多的应用潜力     

Speciation- induced heritable cytosine methylation changes in polyploid wheat

To study possible epigenetic changes accompanying polyploid speciation, genomic DNA from natural polyploid wheats and their putative diploid progenitors were digested with a pair of isoschizomers Hpa II / Msp I and hybridized to 21 different types of low-copy DNA sequences. It was found that cytosine methylation changes were abundant in natural polyploid wheats after their speciation. The hybridization of the same set of sequences to a synthetic hexaploid wheat along with its parental lines indicated that the extensive DNA methylation changes already existed in the early generations (S5, S6 and Sy) of this plant. Moreover, the high similarity of the changed restriction fragment length polymorphism (RFLP) patterns among three randomly chosen individual plants suggested that the methylation changes occurred even earlier, and/or were of a nonrandom nature. The changed patterns were stably inherited in the three successive selfed generations. Though methylation changes are probably a genome-wide occurrence, they appeared to be confined to the specific types of DNA sequences. The possible implications of the rapid and extensive cytosine methylation changes for several attributes of allopolyploid genome evolution, such as genetic diploidization and gene diversification, are discussed .     

Molecular insights into human brain evolution

Rapidly advancing knowledge of genome structure and sequence enables new means for the analysis of specific DNA changes associated with the differences between the human brain and that of other mammals. Recent studies implicate evolutionary changes in messenger RNA and protein expression levels, as well as DNA changes that alter amino acid sequences. We can anticipate having a systematic catalogue of DNA changes in the lineage leading to humans, but an ongoing challenge will be relating these changes to the anatomical and functional differences between our brain and that of our ancient and more recent ancestors.     

Direct estimation of per nucleotide and genomic deleterious mutation rates in Drosophila

Spontaneous mutations are the source of genetic variation required for evolutionary change, and are therefore important for many aspects of evolutionary biology. For example, the divergence between taxa at neutrally evolving sites in the genome is proportional to the per nucleotide mutation rate, u (ref. 1), and this can be used to date speciation events by assuming a molecular clock. The overall rate of occurrence of deleterious mutations in the genome each generation (U) appears in theories of nucleotide divergence and polymorphism, the evolution of sex and recombination, and the evolutionary consequences of inbreeding. However, estimates of U based on changes in allozymes or DNA sequences and fitness traits are discordant. Here we directly estimate u in Drosophila melanogaster by scanning 20 million bases of DNA from three sets of mutation accumulation lines by using denaturing high-performance liquid chromatography. From 37 mutation events that we detected, we obtained a mean estimate for u of 8.4 x 10(-9) per generation. Moreover, we detected significant heterogeneity in u among the three mutation-accumulation-line genotypes. By multiplying u by an estimate of the fraction of mutations that are deleterious in natural populations of Drosophila, we estimate that U is 1.2 per diploid genome. This high rate suggests that selection against deleterious mutations may have a key role in explaining patterns of genetic variation in the genome, and help to maintain recombination and sexual reproduction.     

大蒜的胚胎学研究 Ⅰ.花药的发育和小孢子的发生

大蒜的小孢子是由小孢子母细胞经典型的减数分裂而来。小孢子母细胞减数分裂的胞质分裂为连续型。四分体排列呈平面型。在小孢子母细胞减数分裂过程中出现了多价体、单价体和染色体落后等不规则现象，是导致花粉退化的重要原因     

Developmental constraints versus flexibility in morphological evolution

Evolutionary developmental biology has encouraged a change of research emphasis from the sorting of phenotypic variation by natural selection to the production of that variation through development. Some morphologies are more readily generated than others, and developmental mechanisms can limit or channel evolutionary change. Such biases determine how readily populations are able to respond to selection, and have been postulated to explain stasis in morphological evolution and unexplored morphologies. There has been much discussion about evolutionary constraints but empirical data testing them directly are sparse. The spectacular diversity in butterfly wing patterns is suggestive of how little constrained morphological evolution can be. However, for wing patterns involving serial repeats of the same element, developmental properties suggest that some directions of evolutionary change might be restricted. Here we show that despite the developmental coupling between different eyespots in the butterfly Bicyclus anynana, there is great potential for independent changes. This flexibility is consistent with the diversity of wing patterns across species and argues for a dominant role of natural selection, rather than internal constraints, in shaping existing variation.     

Epigenetics in human disease and prospects for epigenetic therapy

Epigenetic mechanisms, which involve DNA and histone modifications, result in the heritable silencing of genes without a change in their coding sequence. The study of human disease has focused on genetic mechanisms, but disruption of the balance of epigenetic networks can cause several major pathologies, including cancer, syndromes involving chromosomal instabilities, and mental retardation. The development of new diagnostic tools might reveal other diseases that are caused by epigenetic alterations. Great potential lies in the development of 'epigenetic therapies'--several inhibitors of enzymes controlling epigenetic modifications, specifically DNA methyltransferases and histone deacetylases, have shown promising anti-tumorigenic effects for some malignancies.     

Improving DNA damage repair ability ofE. coli to UV-radiosensitivity by DNA-mediated gene transfer of low energy ion beam

Using calcium chloride method of transfer gene as control, a new technique of transferring gene by low energy ion beam has been applied to the study of improving DNA damage repair ability ofE. coli to UV-radiosensitivity. The genome DNA pieces ofDeinococcus radiodurans, as “foreign” genetic materials, were introduced into the UV-radiosensitive strains ofE. coli by implantation of 20 keV Ar⁺ at doses ranging from 1 × 10¹⁵ to 2 × 10¹⁵ ions/cm². Results show that the transfected strains present higher UV-radioresistance than that of un-transfected ones and start ones. The survival rate of transfected strains and their unscheduled DNA synthesis (UDS) ability is increased, indicating that the transfer gene is a success.     

Predator-induced behaviour shifts and natural selection in field-experimental lizard populations

The role of behaviour in evolutionary change has long been debated. On the one hand, behavioural changes may expose individuals to new selective pressures by altering the way that organisms interact with the environment, thus driving evolutionary divergence. Alternatively, behaviour can act to retard evolutionary change: by altering behavioural patterns in the face of new environmental conditions, organisms can minimize exposure to new selective pressures. This constraining influence of behaviour has been put forward as an explanation for evolutionary stasis within lineages and niche conservatism within clades. Nonetheless, the hypothesis that behavioural change prevents natural selection from operating in new environments has never been experimentally tested. We conducted a controlled and replicated experimental study of selection in entirely natural populations; we demonstrate that lizards alter their habitat use in the presence of an introduced predator, but that these behavioural shifts do not prevent patterns of natural selection from changing in experimental populations.     

Detection of DNA methylation changes during seed germination in rapeseed （Brassica napus）

DNA methylation is a common yet important modi- fication of DNA in eukaryotic organisms. DNA methy- lation, especially methylation of cytosine (m5C), have both epigenetic and mutagenic effects on various cellu- lar activities such as differential gene exp…     

Reassembly of shattered chromosomes in Deinococcus radiodurans

Dehydration or desiccation is one of the most frequent and severe challenges to living cells. The bacterium Deinococcus radiodurans is the best known extremophile among the few organisms that can survive extremely high exposures to desiccation and ionizing radiation, which shatter its genome into hundreds of short DNA fragments. Remarkably, these fragments are readily reassembled into a functional 3.28-megabase genome. Here we describe the relevant two-stage DNA repair process, which involves a previously unknown molecular mechanism for fragment reassembly called 'extended synthesis-dependent strand annealing' (ESDSA), followed and completed by crossovers. At least two genome copies and random DNA breakage are requirements for effective ESDSA. In ESDSA, chromosomal fragments with overlapping homologies are used both as primers and as templates for massive synthesis of complementary single strands, as occurs in a single-round multiplex polymerase chain reaction. This synthesis depends on DNA polymerase I and incorporates more nucleotides than does normal replication in intact cells. Newly synthesized complementary single-stranded extensions become 'sticky ends' that anneal with high precision, joining together contiguous DNA fragments into long, linear, double-stranded intermediates. These intermediates require RecA-dependent crossovers to mature into circular chromosomes that comprise double-stranded patchworks of numerous DNA blocks synthesized before radiation, connected by DNA blocks synthesized after radiation.     

拟南芥基因倍增及基因流失分析

基因倍增指基因组中含有基因的DNA片段复制出一个或更多拷贝的过程，是进化出新物种的主要原因。采用新的数据和方法研究拟南芥基因组的基因倍增过程，通过分析串联基因倍增和大规模基因倍增的存在比例和同义置换率分布，并估计大规模倍增后基因流失的比例，揭示了拟南芥基因组一次非常明显的全基因组倍增，采用科学的方法估计这次倍增发生在约8000万年前。比较该结果与之前的研究，提出了一种解释拟南芥基因倍增过程更合理的模型。     

拟南芥基因倍增及基因流失分析

基因倍增指基因组中含有基因的DNA片段复制出一个或更多拷贝的过程,是进化出新物种的主要原因。采用新的数据和方法研究拟南芥基因组的基因倍增过程,通过分析串联基因倍增和大规模基因倍增的存在比例和同义置换率分布,并估计大规模倍增后基因流失的比例,揭示了拟南芥基因组一次非常明显的全基因组倍增,采用科学的方法估计这次倍增发生在约8000万年前。比较该结果与之前的研究,提出了一种解释拟南芥基因倍增过程更合理的模型。     

Fitness benefits of prolonged post-reproductive lifespan in women

Most animals reproduce until they die, but in humans, females can survive long after ceasing reproduction. In theory, a prolonged post-reproductive lifespan will evolve when females can gain greater fitness by increasing the success of their offspring than by continuing to breed themselves. Although reproductive success is known to decline in old age, it is unknown whether women gain fitness by prolonging lifespan post-reproduction. Using complete multi-generational demographic records, we show that women with a prolonged post-reproductive lifespan have more grandchildren, and hence greater fitness, in pre-modern populations of both Finns and Canadians. This fitness benefit arises because post-reproductive mothers enhance the lifetime reproductive success of their offspring by allowing them to breed earlier, more frequently and more successfully. Finally, the fitness benefits of prolonged lifespan diminish as the reproductive output of offspring declines. This suggests that in female humans, selection for deferred ageing should wane when one's own offspring become post-reproductive and, correspondingly, we show that rates of female mortality accelerate as their offspring terminate reproduction.     

美洲黑杨种质材料倍性鉴定

【目的】对美洲黑杨种质资源库保存的种质材料进行倍性评估,并对候选多倍体进行倍性鉴定。【方法】利用9对用于多倍体鉴定的SSR引物检测448份美洲黑杨种质材料,根据每个引物扩增位点的等位基因数目对种质材料的倍性进行评估,基于初步鉴定结果筛选出候选多倍体材料。在此基础上,使用流式细胞仪(FCM)对候选多倍体种质材料的倍性进行鉴定。【结果】分子标记基因型分型统计结果显示,9个SSR位点共扩增出129条多态性条带,每个位点的等位基因数为5(Ploidp-10)~25(Ploidp-07)个,平均每个位点的等位基因数为14.33个。9个SSR位点的多态性信息含量(PIC)变动范围为0.46~0.93,平均PIC值为0.76。在检测的448份美洲黑杨种质材料中,440份美洲黑杨种质材料在9个引物位点上扩增出的等位基因数不多于2个;有8份种质材料在2个引物位点上扩增出了3个不同的等位基因,其中编号为1346、16-42、17-49、18-25的4份种质材料在Ploidp-02引物位点扩增出了3个等位基因,而编号为5-43、5-45、15-14、19-37的另外4份种质材料在Ploidp-04引物位点上也扩增出了3个等位基因。分子检测结果表明:该8份种质材料在对应的染色体区域发生了遗传物质增加现象,为候选三倍体种质材料。用FCM对8份三倍体候选种质材料进行倍性鉴定发现,编号为1346的种质材料为三倍体,其余7份种质材料疑似为发生局部染色片段增加的候选非整倍体。【结论】9对SSR分子标记均具有较高的多态性信息含量,可用于美洲黑杨种质资源多倍体初步筛选,结合FCM检测,可在大量样品中快速筛选出多倍体种质材料。     

表观遗传学研究进展

 概述了表观遗传调节模式、表观遗传调节的效应、植物表观遗传学的研究进展等。在每种细胞中,都会发生一部分特异基因激活、另一部分基因抑制的现象,形成多种基因表达模式。表观遗传指DNA序列不发生变化,而基因表达发生可遗传改变的现象。表观遗传学改变包括DNA甲基化、组蛋白修饰、非编码RNA作用等,产生基因组印记、母性影响、基因沉默、核仁显性、休眠转座子激活等效应。表观遗传变异是环境因素和细胞内遗传物质间交互作用的结果,其效应通过调节基因表达,控制生物学表型来实现。正是因为表观修饰对于维持生物体内环境和各器官系统功能的重要性,表观遗传的异常会引发疾病,这也成为药物和治疗方案设计的着眼点。     

斯万特·帕博：因人类进化遗传学研究获2022诺贝尔生理学或医学奖

因“在已灭绝的古人类的基因组和人类演化方面的发现”，斯万特·帕博获得2022年诺贝尔生理学或医学奖。回顾了人类起源的长久之问、生物测序技术的突破发展和帕博团队的科研历程，明确了其源于兴趣、攻坚克难的古DNA领域探索之路和丰硕成果：首次实现了对已灭绝古人类尼安德特人的全基因组测序，发现了未知古人类丹尼索瓦人，为人类的进化遗传学提供了新证据。帕博对人类进化遗传中基因流动探索的科研历程，展现了严谨的科学精神以及理想的科研生态；他的科研成果和理念，实现了古基因组学跨越学科与时代的价值，也引起了人类未来将去往何方的进一步思考。