GENOME RELATIONS AMONG ELYMUS CANADENSIS,ELYMUS TRITICOIDES,ELYMUS DASYSTACHYS,AND AGROPYRON SMITHII

Hand-emasculated Elymus canadensis pollinated by E. triticoides, E. dasystachys, and Agropyron smithii yielded 15, 21, and 1 viable hybrid seeds from 56, 52, and 52 florets, respectively. The 28-chromosome species—E. canadensis, E. triticoides, and E. dasystachys—behaved meiotically as allotetraploids and consistently formed 14 bivalents at metaphase I. Octoploid A. smithii, 2n = 56, averaged 0.41^I, 27.72^II, and 0.03^IV in 87 metaphase-I cells. Agropyron smithii is apparently an allooctoploid or a segmental autoallooctoploid. Meiosis was similar in the E. canadensis X E. triticoides and E. dasystachys hybrids. Chromosome pairing was very low in both hybrids, about two loosely connected open-ended bivalents per cell, and may not represent genuine homologies. The genomes of E. canadensis are distinctly different from those of E. triticoides and E. dasystachys. The E. canadensis X A. smithii hybrid averaged 13.37^I and 14.31^II in 76 metaphase-I cells. More than half of the bivalents were closed at both ends. Inability to distinguish between auto- and allosyndesis resulted in two interpretations of genome relations. Either A. smithii is an alloploid with two of its four genomes similar to those of E. canadensis, or it is a segmental autoalloploid genomically unrelated to E. canadensis. The first interpretation is favored. Agropyron dasystachyum, or one of its close relatives, and E. triticoides are suggested as possible parents of A. smithii.     

基因组结构信息在动物系统发育研究中的应用

随着人类基因组和一些模式生物、重要经济生物以及大量微生物基因组测序的完成,生物学整体研究业已进入基因组时代.最近5～10年以来,利用基因组结构信息进行系统发育推断的研究形成了分类学和进化生物学中的前沿领域之一.相对于核苷酸或氨基酸序列中的突变而言,基因组的结构变化--内含子的插入/缺失、反转录子的整合、签名序列、基因重复以及基因排序等--是更大空间(或者时间空间)尺度上的相对稀缺的系统发育信息,一般用于科和科以上阶元间的亲缘关系研究.基因组全序列的获得和其中各基因位置的确定有利于将基因组中不同层次的系统发育信息综合起来,利用全面分子证据(total molecular evidence;包括基因组信息,DNA、RNA、蛋白质的序列信息,RNA和蛋白质的高级结构等)进行分子系统学研究.     

CHLOROPLAST DNA POLYMORPHISM AND PHYLOGENY IN THE B GENOME OF GLYCINE SUBGENUS GLYCINE (LEGUMINOSAE)

The B genome of Glycine subgenus Glycine comprises three diploid species whose monophyly is supported by morphological, crossing, and chloroplast DNA (cpDNA) data. Previous cpDNA studies indicated low levels of divergence among these taxa and failed to resolve cladistic relationships among them. More intensive studies of cpDNA variation were initiated, using additional restriction endonucleases and accessions. Results from cladistic analyses of over 50 restriction site characters indicate that there is considerable cpDNA polymorphism within this group of species, with a minimum of 27 plastome types occurring among the 74 accessions sampled. Levels of homoplasy observed in this group are relatively high (15%) for closely related congeneric species. There is only limited congruence between plastome type and taxonomic classification based on morphological characters. Explanations for this lack of concordance include: 1) the early state of taxonomic understanding in this group, 2) lack of resolution in the cpDNA tree caused by homoplasy and the small number of synapomorphic characters, 3) introgression among these interfertile, often sympatric taxa, and 4) maintenance of ancestral cpDNA polymorphisms resulting in shared plastomes among species.     

桦木科植物的系统发育和地理分布

本文对桦木科植物的研究历史作了详细的总结。在钻研文献的基础上,补充了部分系统学资料,使得花序、花、芬粉、叶表皮等各类性状能够在属间进行比较。根据外类群比较、和谐性分析等原则确定了性的演化极性,利用最大同步法和最小平行演化法对桦木科植物进行了分支分析。对各属的现代分布和地史分布作了描述,在此基础上,讨论了桦木科植物的分布中心、起源地、起源的时间和散布途径。作者试图回到遥远的晚白垩纪和早第三纪,从描绘     

根瘤菌基因组结构的多样性及其与系统发育的关系*

研究探讨依据基因组结构对根瘤菌进行系统发育分类的可行性。采用I-CeuI酶切及脉冲场电泳分析确定25株根瘤菌模式菌株的基因组结构,据此对根瘤菌进行聚群,并与16S rRNA聚群结果相比较。依据基因组结构的近似或不同,25株根瘤菌共分为11个基因组型(genome type,GT)。这些基因组型与依据16S rRNA序列的聚群结果大体一致,其不同之处显示了两种方法各自的特点。因此,基因组的物理结构,即本研究中rm纵子的数量及其在基因组上的位置,可作为系统发育关系的标志而用于根瘤菌的分类。     

基于线粒体基因组全序列的鲟形目鱼类(Pisces: Acipenseriformes)的分子系统发育重建

为厘清鲟形目鱼类的系统发育, 研究新测定了中华鲟(Acipenser sinensis)、长江鲟(A. dabryanus)、短吻鲟(A. brevirostrum)、纳氏鲟(A. naccarii)、鳇(Huso dauricus)和匙吻鲟(Polyodon spathula)共6种鲟类的线粒体全基因组序列。联合已测的17种鲟类的线粒体基因组数据, 利用最大似然法和贝叶斯法重建了鲟形目鱼类的分子系统发育关系, 并采用似然值检验对不同的树拓扑结构进行了评价。结果表明, 6种新测鲟类的线粒体基因组大小为16521—16766 bp, 编码13个蛋白质编码基因、22个转运RNA基因和2个核糖体基因, 与大多数已测的鲟类的线粒体基因组结构高度相似。基于23种鲟形目鱼类线粒体基因组数据, 系统发育分析的结果表明: (1)鲟形目的两个科, 匙吻鲟科(Polyodontidae)和鲟科(Acipenseridae)均为单系; (2)鲟科的内部亲缘关系复杂, 鲟属和鳇属的物种均不构成单系群。鲟科鱼类按分子系统发育重建结果可以分为3个类群: 尖吻鲟类(A. sturio - A. oxyrinchus clade)、大西洋鲟类(Atlantic clade)和太平洋鲟类(Pacific clade)。树拓扑结构的检验结果表明, 鲟科的系统发育关系为(尖吻鲟类(太平洋鲟类, 大西洋鲟类))。铲鲟属(Scaphirhynchus)是大西洋鲟类的基部类群。研究也说明线粒体基因组数据在鲟形目鱼类系统与进化研究方面具有重要应用价值。     

真菌亲缘和分类学的进展

本文对真菌的亲缘和分类学进展的概况作了简要的叙述。真菌在亲缘上是一个异质的类群,有着不同的起源。而真菌分类学则吸收超微结构特征,遗传学和分子生物学的论据组成综合的分枝学科。     

雀形目高级阶元分类与起源研究概况

对雀肜目鸟类高级阶元的分类和系统发育的研究进行了简要概述.经典分类与应用分子生物学方法建立的分类系统在高级阶元(总科)有较大差异,但科级的分类基本一致.在雀形目鸟类起源研究方面,古生物学研究结果认为其起源于劳亚古陆;而分子生物学的证据则认为其起源于冈瓦纳古陆.由于化石的证据与"分子钟"的推测年代相差较大,因此对雀形目鸟类的起源还存在争议,但是目前的研究更倾向于"冈瓦纳起源"假说.