The Origin of Life: A Problem of History,Chemistry, and Evolution

The origin of life is a field full of controversies, not only because of our vague understanding concerning the relevant issues, but also, perhaps more often, owing to our dim conceptual framework throughout the whole field. To improve this situation, an in‐depth conceptual dissection is presented here. It is elucidated that, at its core, the origin of life has three aspects. The facts involved in the process are taken as the historical aspect, which is destined to be uncertain and often irrelevant to debate regarding details. The rules involved include two distinct aspects: chemical mechanisms operated in the whole process, while evolutionary mechanisms joined in only after the emergence of the first Darwinian entities – and then accounted for the subsequent buildup of complexity (this cannot be explained solely by natural selection). Basically, we can ask about the possibility of any assumed event in the origin of life: ‘Is it evolutionarily plausible, chemically feasible, and historically likely?’ Clues from any of the three aspects may be quite valuable in directing our explorations on the other two. This conceptual dissection provides a clearer context for the field, which may even be more useful than any sort of specific research.     

哺乳动物抗凝血酶基因的分子特征、微共线性与适应性进化

抗凝血酶(AT)是哺乳动物体内重要的天然抗凝血因子之一,它隶属于丝氨酸蛋白酶抑制物家族,主要参与并调节复杂的血凝过程。基于比较基因组学手段,共挖掘出17个哺乳动物抗凝血酶基因(AT),并剖析了它们的基因结构、微共线性、保守基序、功能结构域、以及系统进化关系。基因结构与微共线分析表明,哺乳动物AT基因具有5-12个外显子,大多数是7个外显子;不同物种AT基因所处区段之间具有较好的共线性。哺乳动物AT蛋白特征分析显示,SERPIN功能结构域与保守基序1、2、3、4、5、8和9存在相互重叠的部分。AT基因进化树揭示基因进化和通常认为的物种进化几乎一致。同时,利用PAML中Codeml的位点特异模型在AT基因中发掘了1个正选择位点328D。     

Hamamelidaceae: Geographic Distribution,Fossil History and Origin

The family Hamamelidaceae is one of the core (or key) groups for studying the phylogeny of Hamamelids. It is an important taxon for the palaeobotanists and the botanists in discussing the origin and early evolution of the angiosperms owing to its strong differentiation of gross and pollen morphological characters. In this paper, the systematic position, modern distribution pattern and fossil history of the genera are analyzed, and the place and time of origin of the family are discussed according to the principle of the unity between the phylogeny and distribution of plants. The paper consists four parts.     

The Origin,Evolution and Distribution of Ligularia Cass. (Compositae)

The genus Ligularia Cass. is one of the large genera in Compositae-SenecioneaeTussilagininae. In subtrib. Tussilaginae, Ligularia is closely related to, but more advanced than, the genus Farfugium Lindl. It includes six sections, 11 series and 129 species. All the taxa are distributed in Asia with only two species extending to Europe. There are 119 species in E. Asia, Comprising 96 % of the world total. The highest concentration of species in E. Asia occurs in the Hengduan Mountains. In this area there are four section, six series and 67 species, of which 61 species are local endemics; thus 66% of sections, 54.5% of series and about 52 % of species in the world occur in this small area, indicating that it is a major distribution centre for Ligularia. According to character analysis, sect. Corymbosae ser. Calthifoliae with 5 species was considered as the most primitive group in this genus, which has reniform leaves, palmate veins, a few large capitula (arranging in Corymb-like inflorescence), and semispherical involucre etc. The primitive species, L. dentata and L. hodgsonii, are distributed from E. Sichuan to Japan via Hubei, Hunnan, Anhui, Fujian. This distribution pattern is consistent with that of its allied genus, Farfugium. According to the principle of common origin, the ancestors of the two genera appeared most probably in the same area. It was inferred that the area from E. Sichuan of China to Japan was the original area of the genus Ligularia, However, on the basis of geological history and the modern distribution of this genus, the author considers that central China with E. Sichuan might be the primary original area of Ligularia. Its dispersal route was mainly along the mountains of southern margin of Asia, with relatively few members dispersed northea stwards to NE. Asia. The origi-nal time of the genus Ligularia was at least not later than the middle Cretaceous.     

VA菌根共生的起源和进化

ＶＡ菌根共生的起源和进化赵之伟（云南大学生物学系,昆明６５００９１）ＯｒｉｇｉｎａｎｄＥｖｏｌｕｔｉｏｎｏｆｔｈｅＶＡＭｙｃｏｒｒｈｉｚａｌＳｙｍｂｉｏｓｉｓ．ＺｈａｏＺｈｉｗｅｉ（ＢｉｏｌｏｇｙＤｅｐａｒｔｍｅｎｔｏｆＹｕｎｎａｎＵｎｉｖｅｒｓｉｔ...     

断裂蛋白质内含子的剪接机制、起源和进化

蛋白质内含子(intein)是具有自我催化活性的蛋白质. 翻译后,通过蛋白质剪接从蛋白质前体中去掉,并以肽键连接两侧蛋白质外显子(extein)形成成熟蛋白质. 断裂蛋白质内含子(split intein)在蛋白质内含子中部区域特定位点发生断裂,形成N端片段和C端片段,分别由基因组上相距较远的两个基因编码. 现在已知,它仅分布于蓝细菌和古细菌中. 断裂蛋白质内含子的N端片段和C端片段通过非共价键(如静电作用)相互识别,重建催化活性中心,介导蛋白质反式剪接. 断裂蛋白质内含子的发现进一步深化了人们对基因表达和蛋白质翻译后成熟过程复杂性的认识,而且它在蛋白质工程、蛋白质药物开发和蛋白质结构与功能研究等方面有非常广泛的应用. 本文试图综述断裂蛋白质内含子的分布、结构特征和剪接机制,并分析其可能的起源和进化途径.     

First Fossil Evidence for the Advance of Replacement Teeth Coupled with Life History Evolution along an Anagenetic Mammalian Lineage

In mammals that grow up more slowly and live longer, replacement teeth tend to appear earlier in sequence than in fast growing mammals. This trend, known as ‘Schultz''s Rule’, is a useful tool for inferring life histories of fossil taxa. Deviations from this rule, however, suggest that in addition to the pace of life history, ecological factors may also drive dental ontogeny. Myotragus balearicus is an extinct insular caprine that has been proved to be an excellent test case to correlate morphological traits with life history. Here we show that Myotragus balearicus exhibits a slow signature of dental eruption sequence that is in agreement with the exceptionally slow life history of this species, thus conforming to ‘Schultz''s Rule’. However, our results also show an acceleration of the absolute pace of development of the permanent incisors in relation to that of the posterior teeth. The rodent-like incisors of Myotragus balearicus erupted early not only in relative but also in absolute terms (chronological age), suggesting that feeding characteristics also plays an important role in dental ontogeny. This is in agreement with ecological hypotheses based on primates. Our study documents a decoupling of the pace of development of teeth in mammals that is triggered by different selection pressures on dental ontogeny. Moreover, we show that Myotragus kopperi from the early Pleistocene (a direct ancestor of the late Pleistocene-Holocene M. balearicus) follows the pattern of first incisor replacement known in living bovids. Hence, the advance in the eruption sequence of the first incisors occurs along the Myotragus evolutionary lineage over a period of about 2.5 Myr. To our knowledge, this is the first fossil evidence of an advance of the emergence of the permanent first incisor along an anagenetic mammalian lineage.     

Origin and Evolution of Rosaceae

Rosaceae. consisting of about 126 genera and 3200 species, is widely distributed in warm temperate and subtropical regions of the Northern Hemisphere, while more than half of the genera are Asiatic and more then 80% of the total number of Asiatic occur in China (Table 1). In this paper, the origin and evolution of Chinese genera is discussed mainly. The principal tendency of the whole family is also described from the point of view of evolution. First of all, the systematic position of Rosaceae in Angiospermae is reviewed. According to the records of paleobotany, rosaceous plants occurred first in the Tertiary, from the early period of Eocene (genera such as Spiraea and Prunus) to the late period of Miocene (e.g. Crataegus, Malus amd Rosa). They have quite a long history in geological data. Where has this big and old family originated and what steps does it stand in the long course of evolution of flowering plants? There are several opinions and explanations by different authors. In this paper, a general survey of the six prevailing classical systems (Table 2) is made to give a brief idea of the position of this family in the Angiospermae and of the relationships between the subfamilies and also the relationships between different genera in each subfamily. At the end of this paper, an attempt is made to analyse and sum up the major evolutionary tendency of the whole family. As generally condidered, Rosaceae originated from Magnoliales, and woody plants of the family still hold a dominant position. For instance, subfamily Spiraeoideae consists of only one herbaceous genus (i.e., Aruncus) and subfamily Rosoideae only a few herbaceous genera. All of these herbaceous genera are derived from the closely related woody genera of the same subfamily. In the course of evolution of Angiospermae, Rosaceae stands at the initial to the middle stages of development. All parts of plant body in this family are at the chang ing and developing stages, with carpels, fruits and inflorescences being the most active. The primitive types in this family, such as the members of subfamily Spiraeoideae, usually have 5 and free carpels, the number of which are either reduced to 2-1 or increased to 10-numerous. They have different levels of union and are either completely free from each other or coherent at base. The carpels usually occur on the upper part of the receptacle, because the shapes of receptacle are variable, sometimes disk-shaped, cupshaped, tube-shaped or even bottle-shaped. In the last case carpels grow inside the receptacle. Thus the position of carpels has changed from superior to inferior through halfsuperior. In accordance with the development of the carpels, various kinds of fruits are produced. The primitive types of fruit are follicles, with dry, dehiscent carpels opened along different sutures. The next step, the carpels have developed into an indehiscent, I-celled and l-seeded fruit, the so-caned achene. In different genera, the achenes have different coat types and appendages to facilitate dispersing the seeds. Some of the achenes grow upon the fleshy receptacle (like strawberry) and some of them inside the fleshy receptacle (like rose). Sometimes a few carpels are united with the receptacle and develop into a pome (like apple and pear). Another direction of the fruit development is the single carpel with fleshy exocarp and mesocarp, and a bony endocarp, then becoming a drupe (like peach and plum). In addition to fleshy receptacle of thickened fruit coats, they usually have showy colour, fragrant smell and also plenty of sugars, acids, vitamins, etc. which are edible and attract animals and human beings to assist the dispersion of seeds. In this family, there are various types of flower arrangements, both indefinite inflorescences including raceme, umbel, corymb and panicle, and the definite inflorescence, such as solitary flower, cyme and compound cyme. In the evolution course, they tend to change mostly from multiflowered compound inflorescence towards few-flowered simple inflorescence, and finally becoming a solitary flower: simultaneously with the decreasing of number of flowers on the inflorescence, the increasing of size of petals, which become very showy for attraction of insects so as to guarantee pollination and fertilization of the plants concerned. Another tendency, if the bisexual flowers change to unisexual, either monoecious- or dioecious-polygamous, then they form a dense spike which is beneficial to cross pollination. The abundance, diversity, and wide range of distribution of the species and genera of Rosaceae are considered mainly resulted from their highly developed reproductive organs.     

植物与植食动物的相互作用系统

植物与植食动物的相互作用系统王桂明,钟文勤,周庆强（中国科学院动物研究所,北京１０００８０）Ｐｌａｎｔ－ＨｅｒｂｉｖｏｒｏｕｓＭａｍｍａｌＩｎｔｅｒａｃｔｉｏｎＳｙｓｔｅｍ．￥ＷａｎｇＧｕｉｍｉｎｇ;ＺｈｏｎｇＷｅｎｑｉｎ;ＺｈｏｕＱｉｎｇｑｉａｎｇ...