单细胞真核生物的miRNA系统及其进化意义

miRNA 系统在高等多细胞真核生物中得到了广泛深入的研究。近年来,人们在单细胞真核生物上的miRNA研究也取得了重要进展。这不仅丰富了人们对miRNA在整个生物界中的认识,更重要的是对于揭示miRNA这一表达调节系统是如何在生物界中起源进化的问题具有重要意义。该文结合作者在最低等单细胞真核生物——贾第虫上的研究结果,对该领域的研究进展作一概述,并对有关miRNA这一系统的起源进化问题进行了探讨。     

植物nrDNA ITS致同进化不完全现象及其进化意义

nrDNA是个多基因家族,在基因内往往有成千上万的拷贝,但通常只包含有一种序列,即所谓致同进化.因此,nrDNA ITS被广泛应用于植物系统与进化研究当中.近年来,部分研究发现,一些植物类群的基因组内nrDNA ITS也存在着较高的多样性,即致同进化不完全现象.该文就裸子植物和被子植物中nrDNA ITS存在致同进化不完全现象的原因和特点,nrDNA ITS假基因的识别,以及其进化意义等进行了综述.     

Unraveling the Entry Mechanism of Baculoviruses and Its Evolutionary Implications

The entry of baculovirus budded virus into host cells is mediated by two distinct types of envelope fusion proteins (EFPs), GP64 and F protein. Phylogenetic analysis suggested that F proteins were ancestral baculovirus EFPs, whereas GP64 was acquired by progenitor group I alphabaculovirus more recently and may have stimulated the formation of the group I lineage. This study was designed to experimentally recapitulate a possible major step in the evolution of baculoviruses. We demonstrated that the infectivity of an F-null group II alphabaculovirus (Helicoverpa armigera nucleopolyhedrovirus [HearNPV]) can be functionally rescued by coinsertion of GP64 along with the nonfusogenic F^def (furin site mutated HaF) from HearNPV. Interestingly, HearNPV enters cells by endocytosis and, less efficiently, by direct membrane fusion at low pH. However, this recombinant HearNPV coexpressing F^def and GP64 mimicked group I virus not only in its EFP composition but also in its abilities to enter host cells via low-pH-triggered direct fusion pathway. Neutralization assays indicated that the nonfusogenic F proteins contribute mainly to binding to susceptible cells, while GP64 contributes to fusion. Coinsertion of GP64 with an F-like protein (Ac23) from group I virus led to efficient rescue of an F-null group II virus. In summary, these recombinant viruses and their entry modes are considered to resemble an evolutionary event of the acquisition of GP64 by an ancestral group I virus and subsequent adaptive inactivation of the original F protein. The study described here provides the first experimental evidence to support the hypothesis of the evolution of baculovirus EFPs.     

Unique Dental Morphology of Homo floresiensis and Its Evolutionary Implications

Homo floresiensis is an extinct, diminutive hominin species discovered in the Late Pleistocene deposits of Liang Bua cave, Flores, eastern Indonesia. The nature and evolutionary origins of H. floresiensis’ unique physical characters have been intensively debated. Based on extensive comparisons using linear metric analyses, crown contour analyses, and other trait-by-trait morphological comparisons, we report here that the dental remains from multiple individuals indicate that H. floresiensis had primitive canine-premolar and advanced molar morphologies, a combination of dental traits unknown in any other hominin species. The primitive aspects are comparable to H. erectus from the Early Pleistocene, whereas some of the molar morphologies are more progressive even compared to those of modern humans. This evidence contradicts the earlier claim of an entirely modern human-like dental morphology of H. floresiensis, while at the same time does not support the hypothesis that H. floresiensis originated from a much older H. habilis or Australopithecus-like small-brained hominin species currently unknown in the Asian fossil record. These results are however consistent with the alternative hypothesis that H. floresiensis derived from an earlier Asian Homo erectus population and experienced substantial body and brain size dwarfism in an isolated insular setting. The dentition of H. floresiensis is not a simple, scaled-down version of earlier hominins.     

Pelage Color Variation of Macaca arctoides and Its Evolutionary Implications

Stump-tailed macaques (Macaca arctoides) exhibit significant intraspecific variation in pelage color. Based on their pelage color and geographical distribution, they are classified into 2 subspecies: northern bright brown Macaca arctoides arctoides and southern black Macaca arctoides melanota. However, studies on the natural population are extremely scarce, and researchers have occasionally questioned the subspecific classification. We quantitatively examined pelage color variation of Macaca arctoides in 3 free-ranging populations in Thailand. Pelage color difference between populations is significant. The population distributed south of the Isthmus of Kra showed wide intrapopulational variation, including bright brown, dark brown, and completely black, whereas the northern populations primarily had dark brown hairs. Thus, we conclude that one cannot classify the color variants into subspecies. Further, we hypothesize that the distinctive polymorphism in southern Thailand resulted from geographical isolation caused by the Pleistocene eustatic fluctuations and subsequent recovery of land connection and subsequent gene flow.     

秋枫属的染色体数目及其进化意义

对秋枫属两个种Bischofia javanica和B·polycarpa的体细胞进行了染色体计数研究。结果表明这两个种在形态学上虽然存在差异,如秋枫是圆椎花序,重阳木是总状花序,但染色体数目均为2n=196。同时,结合细胞学、形态学和生态学特点探讨了秋枫属的染色体基数,多倍化的起源及其演化意义。     

On Pluralism and Competition in Evolutionary Explanations

A controversy arose concerning the adaptive significance ofclitoral orgasm, disputing whether the presence of the traitin females is explained by appeal to developmental processesor natural selection (Gould, 1987a, b; Alcock, 1987). In response,Sherman (1988) offered a pluralistic solution in terms of levelsof analysis in which Gould and Alcock's disagreement was construedas semantic and not substantial. I argue that Sherman's solutionis mistaken. I suggest that the nature of the Gould/Alcock disputeis better understood by considering the abstract structure ofscientific theories and their role in explanation. This accountleads to a representation of science as having a plurality oftheoretical models which are integrated piecemeal in the explanationof concrete phenomena.     

Effects of Competition and Temporal Variation on the Evolutionary Potential of Two Native Bunchgrass Species

The capacity of restored plant populations to adapt to new environmental challenges depends on within‐population genetic variation. We examined how much genetic and environmentally based variation for fitness‐associated traits exists within populations of two native grasses commonly used for restoration in California. We were also interested in understanding how phenotypic expression of genetic variation for these traits varies with growth environment. Thirty maternal families of Elymus glaucus (Blue wild rye) and Nassella pulchra (Purple needlegrass) were sampled from both coastal and interior populations and reciprocally transplanted into three replicated common gardens with and without interspecific competition at each site. Reproductive output of families differed both among years and with competition treatments. Phenotypic expression of genetic variation in culm production differed among populations and was very low when families were grown with interspecific competition. Without interspecific competition, the degree of genetic determination peaked in year two in both species (8.4 and 15.1% in E. glaucus and N. pulchra, respectively). Significant genetic differences in reproduction and phenotypic plasticity were found among N. pulchra subpopulations sampled less than 3 km apart, further highlighting the importance of thoroughly sampling available genetic variation in populations used for restoration. The variable and generally low expression of genetic variation indicates that rates of adaptation in restored populations of these native grasses may vary temporally and may be especially slow within competitive environments.     

The Early Origin of the Antarctic Marine Fauna and Its Evolutionary Implications

The extensive Late Cretaceous – Early Paleogene sedimentary succession of Seymour Island, N.E. Antarctic Peninsula offers an unparalleled opportunity to examine the evolutionary origins of a modern polar marine fauna. Some 38 modern Southern Ocean molluscan genera (26 gastropods and 12 bivalves), representing approximately 18% of the total modern benthic molluscan fauna, can now be traced back through at least part of this sequence. As noted elsewhere in the world, the balance of the molluscan fauna changes sharply across the Cretaceous – Paleogene (K/Pg) boundary, with gastropods subsequently becoming more diverse than bivalves. A major reason for this is a significant radiation of the Neogastropoda, which today forms one of the most diverse clades in the sea. Buccinoidea is the dominant neogastropod superfamily in both the Paleocene Sobral Formation (SF) (56% of neogastropod genera) and Early - Middle Eocene La Meseta Formation (LMF) (47%), with the Conoidea (25%) being prominent for the first time in the latter. This radiation of Neogastropoda is linked to a significant pulse of global warming that reached at least 65°S, and terminates abruptly in the upper LMF in an extinction event that most likely heralds the onset of global cooling. It is also possible that the marked Early Paleogene expansion of neogastropods in Antarctica is in part due to a global increase in rates of origination following the K/Pg mass extinction event. The radiation of this and other clades at ∼65°S indicates that Antarctica was not necessarily an evolutionary refugium, or sink, in the Early – Middle Eocene. Evolutionary source – sink dynamics may have been significantly different between the Paleogene greenhouse and Neogene icehouse worlds.     

Sequence of the Pearl Oyster Carbonic Anhydrase-Related Protein and Its Evolutionary Implications

Carbonic anhydrases are conserved in vertebrates and invertebrates, and a noncatalytic carbonic anhydrase-related protein VIII (CARP VIII) has been found in deuterostomes and the phylum Placozoa. I isolated a cDNA encoding a noncatalytic CARP from the mantle of the pearl oyster Pinctada fucata. The polypeptide (CARP-1) predicted from the nucleotide sequence shares 44-60% identity with known CARP VIII sequences, and its phylogenetic analysis showed that P. fucata formed a single group with deuterostome invertebrates. However, since CARP VIII sequences are not identified in protostomes, these results suggest that CARP-1 may have originated in molluscs independently from deuterostome CARP VIII sequences.     

Microbiome‐Germline Interactions and Their Transgenerational Implications

It is becoming increasingly clear that most, if not all, animals and plants are associated with a diverse array of resident gut microbiota. This symbiosis is regulated by host‐microbiome interactions which influence the development, homeostasis, adaptation and evolution of the host. Recent evidence indicated that these interactions can also affect the host germline and have a potential of supporting transgenerational effects, including inheritance of acquired characteristics. Taken together, the influence of gut bacteria on the host soma and germline could potentially give rise to emergent phenotypes, which may be partially inherited by three distinguishable modes of transgenerational influence of gut bacteria: 1) “soma‐to‐soma” 2) “soma‐to‐germline” and 3) “soma‐germline‐soma”. Here, we discuss these possibilities in light of evidence supporting bacterial‐mediated modes of transgenerational inheritance.

     

Fever in Ectotherms: Evolutionary Implications

Fever, an elevated thermoregulatory "set-point," occurs in vertebratesfrom fishes through mammals in response to infection with appropriatepathogens. The long phylogenetic history of fever supports thehypothesis that fever has an adaptive or beneficial role (i.e.,fever is a component of the host's immunological defenses).Besides providing insight into determining the role of feverin disease, ectothermic vertebrates have also served as excellentanimal models to specifically answer many questions relatingto fever and disease. For example, survival studies using goldfishes,lizards, and newborn mammals which are also virtually ectothermic)have shown that an elevated body temperature increases the survivalrate of the infected organism. Furthermore, by using ectothermsit has been possible to demonstrate that the reduction in serumiron which accompanies most infections is not directly attributableto an elevation in body temperature. Nevertheless, a rise inbody temperature, coupled with a fall in serum iron, appearsto constitute a coordinated host defense mechanism in responseto at least some bacterial infections in reptiles and mammals,and perhaps other groups of vertebrates.     

An Evolutionary Perspective on Linoleic Acid Synthesis in Animals

The diet of organisms generally provides a sufficient supply of energy and building materials for healthy growth and development, but should also contain essential nutrients. Species differ in their exogenous requirements, but it is not clear why some species are able to synthesize essential nutrients, while others are not. The unsaturated fatty acid, linoleic acid (LA; 18:2n-6) plays an important role in functions such as cell physiology, immunity, and reproduction, and is an essential nutrient in diverse organisms. LA is readily synthesized in bacteria, protozoa and plants, but it was long thought that all animals lacked the ability to synthesize LA de novo and thus required a dietary source of this fatty acid. Over the years, however, an increasing number of studies have shown active LA synthesis in animals, including insects, nematodes and pulmonates. Despite continued interest in LA metabolism, it has remained unclear why some organisms can synthesize LA while others cannot. Here, we review the mechanisms by which LA is synthesized and which biological functions LA supports in different organisms to answer the question why LA synthesis was lost and repeatedly gained during the evolution of distinct invertebrate groups. We propose several hypotheses and compile data from the available literature to identify which factors promote LA synthesis within a phylogenetic framework. We have not found a clear link between our proposed hypotheses and LA synthesis; therefore we suggest that LA synthesis may be facilitated through bifunctionality of desaturase enzymes or evolved through a combination of different selective pressures.     

Indoor-Breeding of Aedes albopictus in Northern Peninsular Malaysia and Its Potential Epidemiological Implications

Background

The mosquito Ae. albopictus is usually adapted to the peri-domestic environment and typically breeds outdoors. However, we observed its larvae in most containers within homes in northern peninsular Malaysia. To anticipate the epidemiological implications of this indoor-breeding, we assessed some fitness traits affecting vectorial capacity during colonization process. Specifically, we examined whether Ae. albopictus exhibits increased survival, gonotrophic activity and fecundity due to the potential increase in blood feeding opportunities.

Methodology/Principal Findings

In a series of experiments involving outdoors and indoors breeding populations, we found that Ae. albopictus lives longer in the indoor environment. We also observed increased nighttime biting activity and lifetime fecundity in indoor/domestic adapted females, although they were similar to recently colonized females in body size.

Conclusion/Significance

Taken together these data suggest that accommodation of Ae. albopictus to indoor/domestic environment may increase its lifespan, blood feeding success, nuisance and thus vectorial capacity (both in terms of increased vector-host contacts and vector population density). These changes in the breeding behavior of Ae. albopictus, a potential vector of several human pathogens including dengue viruses, require special attention.     

毛蚶与青蚶精子超微结构及其所反映的蚶科进化关系

应用透射电镜技术,比较研究了毛蚶与青蚶精子的超微结构。毛蚶精子顶体为圆锥形,约为核长的1／2;精核无核前窝,具核后窝;中段横切面常见5个(偶见4个)线粒体环绕于中心粒周围;精子末段由轴丝及包绕轴丝的质膜组成,轴丝为典型的“9 2”结构。青蚶精子顶体轴向纵切面呈伞状,覆盖于细胞核前端,约为核长的1／3;精核具核前窝和核后窝;中段横切面常见有5个(偶见6个)线粒体环绕于中心粒周围;末段结构同毛蚶。顶体的形态、核前窝和核后窝的有无、中段线粒体的数量等是探索蚶科动物种间进化关系的线索。     

Nucleotide Substitution Patterning within the Meloidogyne rDNA D3 Region and Its Evolutionary Implications

Evolutionary relationships based on nucleotide variation within the D3 26S rDNA region were examined among acollection of seven Meloidogyne hapla isolates and seven isolates of M. arenaria, M. incognita, and M. javanica. Using D3A and D3B primers, a 350-bp region was PCR amplified from genomic DNA and double-stranded nucleotide sequence obtained. Phylogenetic analyses using three independent clustering methods all provided support for a division between the automictic M. hapla and the apomictic M. arenaria, M. incognita, and M. javanica. A nucleotide sequence character distinguishing M. hapla from the three apomictic species was a 3-bp insertion within the interior of the D3 region. The three apomictic species shared a common D3 haplotype, suggesting a recent branching. Single M. hapla individuals contained two different haplotypes, differentiated by a Sau3AI restriction site polymorphism. Isolates of M. javanica appeared to have only one haplotype, while M. incognita and M. arenaria maintained more than one haplotype in an isolate.     

原始生物大分子动态的数学模型及其进化意义

本文应用生态学上关于种群增长及种间竞争的逻辑斯缔方程,提出原始生物大分子动态的数学模型,对从该模型推导得的几种可能结果进行了分析,得出在生命起源初期的原始生物圈的生物多样性是很低的结论,即原始生物圈中较大量存在的只是一些种类单一的,可复制的原始生物大分子,因此,可以认为生物进化就是建立在这样的一个基础上,并沿着生物多样性不断提高的途径演化,该模型还有助于对广泛存在于现代生物基因组中的重复序列的起源的认识。     

Functional Morphology of the Phallosome in Glossina (Diptera, Glossinidae) and Its Evolutionary Implications

Current views on the phylo-genetjc relations of the three species groups within the genus Glossina are critically reviewed. In respect of the male genitalia, the fusca group is here regarded as more specialized than the morsitans group. The detailed phallosome morphology of G. austeni is compared with that of G. fuscipes , on the basis of their mode of action in living flies. The comparison is extended to fusca group species, using dead material only. The presumed phylogeny of Glossina is presented in outline; the evolution of the genus has involved a progressive invasion of riverine and later of forest habitats, from an original semi-arid grassy woodland habitat.     

Phylogenetic and Biochemical Studies Reveal a Potential Evolutionary Origin of Small Heat Shock Proteins of Animals from Bacterial Class A

Small heat shock proteins (sHSPs), as one subclass of molecular chaperones, are important for cells to protect proteins under stress conditions. Unlike the large HSPs (represented by Hsp60 and Hsp70), sHSPs are highly divergent in both primary sequences and oligomeric status, with their evolutionary relationships being unresolved. Here the phylogenetic analysis of a representative 51 sHSPs (covering the six subfamilies: bacterial class A, bacterial class B, archae, fungi, plant, and animal) reveals a close relationship between bacterial class A and animal sHSPs which form an outgroup. Accumulating data indicate that the oligomers from bacterial class A and animal sHSPs appear to exhibit polydispersity, while those from the rest exhibit monodispersity. Together, the close evolutionary relationship and the similarity in oligomeric polydispersity between bacterial class A and animal sHSPs not only suggest a potential evolutionary origin of the latter from the former, but also imply that their oligomeric polydispersity is somehow a property determined by their primary sequences. [Reviewing Editor: Dr. Martin Kreitman]