Synthesis of internal re-initiation fragments of beta-galactosidase in vitro and in vivo.

Internal re-initiation polypeptides which are products of the lacZ gene of Escherichia coli have been synthesized in a DNA-directed cell-free protein synthesis system. Some of the properties of these protein fragments have been characterized. The de novo synthesized re-initiation proteins, unlike both in vitro synthesized wild-type β-galactosidase and nonsense termination fragments, are insoluble when synthesized at 37 °C, but soluble if synthesis takes place at 25 °C. The same re-initiation proteins which are made in vivo have been detected in vitro. Unlike their in vivo counterparts, which are degraded rapidly, the in vitro synthesized restart proteins are completely stable for at least one hour following their synthesis. Both in vivo and in vitro, the re-initiation proteins are not synthesized from DNA containing a wild-type Z gene, but require a specific nonsense mutation in order to be expressed. Furthermore, the location of the mutation within the Z gene is very important in determining whether or not re-initiation will occur at a given site.Several nonsense mutations which do not result in the synthesis of detectable amounts of restart protein in vivo produce specific re-initiation polypeptides in vitro. These restart proteins display many of the same properties as do those which are made both in vivo and in vitro: they are not made from wild-type DNA, and they are only made from DNA containing a specific nonsense mutation. One of these mutations is 118, which is an extreme polar mutation in vivo. Another is 545, which synthesizes a restart protein in vivo if, and only if, it is coupled with a secondary mutation, π(1). π(1) thus appears to be necessary for the synthesis of a particular re-initiation protein in vivo but unnecessary for the synthesis of the same protein in vitro. The efficiencies of re-initiation vary at the different sites, but in all cases are less than the initiation frequency at the start of the gene. The experiments thus show that when complicating factors, such as polarity and protein degradation, are eliminated, translational re-initiation can be detected at many sites in the lacZ gene.     

黄土高原不同树种枯落叶混合分解效应

混交林中不同树种枯落物混合分解是否产生促进或抑制作用是评价种间关系和混交适宜性的重要依据之一。以黄土高原主要树种为对象,通过室内枯落叶混合分解模拟试验,结果表明:(1)沙棘、白榆、柠条和小叶杨枯落叶分解最快(周转期1 a左右),其次为旱柳、侧柏和白桦枯落叶(周转期略大于1 a),紫穗槐、辽东栎和刺槐枯落叶分解稍慢(周转期1.5 a左右),而樟子松、落叶松和油松枯落叶分解最慢(周转期略大于2 a)。(2)对于针叶树,与油松枯落叶混合,存在明显促进分解作用的是侧柏、落叶松,其次是白桦、沙棘和刺槐;与樟子松枯落叶混合,存在明显促进分解作用的是落叶松、侧柏、沙棘、白榆,其次是柠条、紫穗槐和小叶杨,而存在明显抑制分解作用的是刺槐,其次是白桦和辽东栎;与落叶松枯落叶混合,存在较明显促进分解作用的是白榆、白桦和辽东栎,存在较明显抑制作用的是刺槐;紫穗槐与侧柏枯落叶混合存在较明显的抑制分解作用。(3)对于阔叶树,与小叶杨枯落叶混合,存在较明显促进分解作用的是紫穗槐,其次是辽东栎和刺槐;与刺槐枯落叶混合,存在较明显促进分解作用的是白榆和沙棘,存在明显抑制分解作用的是柠条,其次是辽东栎和白桦;与白桦枯落叶混合,存在较明显促进分解作用的是辽东栎和紫穗槐,存在较明显抑制分解作用的是柠条;白榆与辽东栎、旱柳枯落叶混合均存在较明显的促进分解作用,而白榆与柠条枯落叶混合存在较明显的抑制分解作用;紫穗槐与旱柳、沙棘枯落叶混合均存在较明显的促进分解作用,而紫穗槐与柠条枯落叶混合有较明显的抑制作用。     

More Sex-Determination Mutants of CAENORHABDITIS ELEGANS

Sex determination in Caenorhabditis elegans is controlled by the X chromosome: autosome ratio, i.e. 2A;XX animals are hermaphrodite, and 2A;XO animals are male. A procedure for isolating 2A;XO animals that are transformed into hermaphrodites has been developed. Nine mutations causing this transformation have been obtained: eight are recessive, and all of these fall into a new autosomal complementation group, her-1 V. The remaining mutation (her-2) is dominant and has a genetic map location similar to that of tra-1 III. Recessive mutations of tra-1 cause the reverse transformation, transforming 2A;XX animals into males. Therefore, the her-2 mutation may result in constitutive expression of tra-1. Mutations in her-1 are without effect on XX animals, but the her-2 mutation prevents sperm production in both XX and XO animals, in addition to its effect on the sexual phenotype of XO animals. The epistatic relationships between tra and her genes are used to deduce a model for the action of these genes in controlling sex determination.     

Polyphyly of Asian Tree Toads,Genus Pedostibes Günther, 1876 (Anura: Bufonidae), and the Description of a New Genus from Southeast Asia

The Asian Tree Toad genus Pedostibes, as currently understood, exhibits a conspicuously disjunct distribution, posing several immediate questions relating to the biogeography and taxonomy of this poorly known group. The type species, P. tuberculosus and P. kempi, are known only from India, whereas P. hosii, P. rugosus, and P. everetti are restricted to Southeast Asia. Several studies have shown that these allopatric groups are polyphyletic, with the Indian Pedostibes embedded within a primarily South Asian clade of toads, containing the genera Adenomus, Xanthophryne, and Duttaphrynus. Southeast Asian Pedostibes on the other hand, are nested within a Southeast Asian clade, which is the sister lineage to the Southeast Asian river toad genus Phrynoidis. We demonstrate that Indian and Southeast Asian Pedostibes are not only allopatric and polyphyletic, but also exhibit significant differences in morphology and reproductive mode, indicating that the Southeast Asian species’ are not congeneric with the true Pedostibes of India. As a taxonomic solution, we describe a new genus, Rentapia gen. nov. to accommodate the Southeast Asian species.     

Publication of descriptions of novel bacterial taxa in <Emphasis Type="Italic">Antonie van Leeuwenhoek</Emphasis>

The species from the order Neisseriales are currently distinguished from other bacteria on the basis of branching in 16S rRNA gene trees. For this order containing a single family, Neisseriaceae, no distinctive molecular, biochemical, or phenotypic characters are presently known. We report here detailed phylogenetic and comparative analyses on the 27 genome sequenced species of the order Neisseriales. Our comparative genomic analyses have identified 54 conserved signature indels (CSIs) in widely distributed proteins that are specific for either all of the sequenced Neisseriales species or a number of clades within this order that are also supported by phylogenetic analyses. Of these CSIs, 11 are specifically present in all of the sequenced species from this order, but are not found in homologous proteins from any other bacteria. These CSIs provide novel molecular markers specific for, and delimiting, this order. Twenty-one CSIs in diverse proteins are specific for a group comprised of the genera Neisseria, Eikenella, Kingella, and Simonsiella (Clade I), which are obligate host-associated organisms, lacking flagella and exhibiting varied morphology. The species from these genera also formed a strongly supported clade in phylogenetic trees based upon concatenated protein sequences; a monophyletic grouping of these genera and other genera displaying similar morphological characteristics was also observed in the 16S rRNA gene tree. A second clade (Clade II), supported by seven of the identified CSIs and phylogenetic trees based upon concatenated protein sequences, grouped together species from the genera Chromobacterium, Laribacter, and Pseudogulbenkiania that are rod-shaped bacteria, which display flagella-based motility and are capable of free living. The remainder of the CSIs were uniquely shared by smaller groups within these two main clades. Our analyses also provide novel insights into the evolutionary history of the Neisseriales and suggest that the CSIs that are specific for the Clade I species may play an important role in the evolution of obligate host-association within this order. On the basis of phylogenetic analysis, the identified CSIs, and conserved phenotypic characteristics of different Neisseriales genera, we propose a division of this order into two families: an emended family Neisseriaceae (corresponding to Clade I) containing the genera Alysiella, Bergeriella, Conchiformibius, Eikenella, Kingella, Neisseria, Simonsiella, Stenoxybacter, Uruburuella and Vitreoscilla and a new family, Chromobacteriaceae fam. nov., harboring the remainder of the genera from this order (viz. Andreprevotia, Aquaspirillum, Aquitalea, Chitinibacter, Chitinilyticum, Chitiniphilus, Chromobacterium, Deefgea, Formivibrio, Gulbenkiania, Iodobacter, Jeongeupia, Laribacter, Leeia, Microvirgula, Paludibacterium, Pseudogulbenkiania, Silvimonas, and Vogesella).     

The Coefficient of Thermal Conductivity of Blood and of Various Tissues

A method for measuring K, the coefficient of thermal conductivity, for a variety of dog tissues is described. The values of K for muscle and liver are larger than that for water, the value of K for lung is smaller than that for water and the values of K for brain, plasma, and blood are about the same as that of water. The values found for K are given in a table.     

Dominant Suppressors of a Muscle Mutant Define an Essential Gene of CAENORHABDITIS ELEGANS

The sup-11 I locus of C. elegans was defined by rare dominant suppressors of unc-93(e1500) III, a mutation that affects muscle structure. All ten of these dominant suppressors have a recessive "scrawny" phenotype. Two additional classes of sup-11 alleles were identified. One class, null alleles, was obtained by reversion of the dominant suppressor activity. These null alleles are recessive embryonic lethals, indicating that sup-11 is an essential gene. Members of the second class, rare semidominant revertants of the "scrawny" phenotype, are partial suppressors of unc-93(e1500). The genetic properties of the dominant suppressor mutations suggest that they are rare missense mutations that confer a novel activity to the sup-11 protein. We consider some of the ways that sup-11 alleles might suppress unc-93(e1500), including the possibilities that the altered sup-11 proteins restore function to a protein complex or are modified products of a gene that is a member of an unc-93 gene family.     

Genetic analysis of transpositions in the lac region of Escherichia coli

The lac region of Escherichia coli, carried on an F′ lacproB episome, was used as a target for the transposition of several transposable elements. Tn9 shows a preferential integration (by a factor of 50) into a region extending from the end of the Z gene through the Y gene. Throughout the remainder of the lacI, Z and Y genes one other short region, located in the middle of the I gene, is favored for integration. Within these favored regions many different integration points are evident. Inspection of the DNA sequence for the I and Y genes, and parts of the Z gene, shows a strong correlation between A + T richness and regions of preferential integration. Tn5 insertions follow a similar pattern, although with less preference; whereas Tn10 insertions (provided by T. J. Foster), also favor the Y gene and the end of Z, but are distributed among fewer integration points. Most of the Tn3 insertions into the episome are accompanied by a nearby or adjacent deletion.     

A classification of the New World species of Aster (Asteraceae)

In order effectively to list and comment on the results of cytological investigations inAster in a companion paper, a scheme of infrageneric classification is presented which utilizes the basic chromosome number as a pivotal diagnostic character. Reasons are stated as to why, with the exception ofUnamia Greene which is transferred toSolidago, and the commonly recognized generaLeucelene Greene,Machaeranthera Nees andXylorhiza Nutt., none of the segregate genera previously proposed or recorded in the literature is upheld. Instead, these taxa are being given subgeneric or sectional rank. Two additional subgenera are established to accommodate the species groups traditionally placed in “Aster proper,” which are characterized by having basic chromosome numbers ofx = 5 andx = 8, respectively. Altogether ten subgenera of the genusAster, five of them subdivided further into a total of 24 sections, are recognized as having representative species in the New World. All basionyms and type species are listed, and a number of new combinations and status changes are validated in accordance with the International Rules of Botanical Nomenclature. Where known (from literature and personal research), chromosome numbers are recorded for the species.     

Getting rid of interventions

According to James Woodward’s influential interventionist account of causation, X is a cause of Y iff, roughly, there is a possible intervention on X that changes Y. Woodward requires that interventions be merely logically possible. I will argue for two claims against this modal character of interventions: First, merely logically possible interventions are dispensable for the semantic project of providing an account of the meaning of causal statements. If interventions are indeed dispensable, the interventionist theory collapses into (some sort of) a counterfactual theory of causation. Thus, the interventionist theory is not tenable as a theory of causation in its own right. Second, if one maintains that merely logically possible interventions are indispensable, then interventions with this modal character lead to the fatal result that interventionist counterfactuals are evaluated inadequately. Consequently, interventionists offer an inadequate theory of causation. I suggest that if we are concerned with explicating causal concepts and stating the truth-conditions of causal claims we best get rid of Woodwardian interventions.     

Estimates of Inbreeding in a Natural Population: A Comparison of Sampling Properties

The average inbreeding coefficient f of a population can be estimated in several different ways based solely on the genotypic frequencies at a single locus. The means and variances of four different estimates have been compared. While the four estimates are equivalent when there are two alleles, the best estimates when there are three or more alleles are based upon total heterozygosity (see PDF) where x and y are the expected and observed number of heterozygotes) and the proportion of alleles that are homozygous (see PDF) where k = the number of alleles, a_ii = the number of A_iA_i homozygotes, and 2a_ij = the number of A_iA_j heterozygotes). Both are minimally biased estimates of f and have identical sampling variances when all alleles are equally frequent. However, when alleles have different frequencies, the choice between these two estimates depends on the gene frequencies and the true inbreeding coefficient of a population; f₂ is the best estimate when the true average inbreeding coefficient is suspected to be low or f = 0, while f₁ is best in populations with large average inbreeding coefficients. Approximate sampling variances of these two estimates are given for any f and any number of alleles with arbitrary gene frequencies; these approximations are accurate for samples as small as n = 100. The chi-square and maximum likelihood estimates of f are not as good for realistic sample sizes.     

A revision of European saxicolous species of the genus Buellia de Not. and formerly included genera

Abstract: A detailed taxonomic survey of the saxicolous European species of Buellia based on a detailed survey and assessment of the important features of the genus is presented. These include the conidia, the anatomy of the exciple, the spore wall pigmentation, ornamentation and internal wall thickening, as well as analysis of the lichen substances. As a result, 36 saxicolous species are recognized, of which Buellia griseosquamulata and B. longispora are new taxa and B. atrocinerella and B. parvula are new combinations. Buellia coniops, B. lecideina and B. punctata are transferred to the validated genus Amandinea. A key to 43 accepted species of Buellia, Amandinea and Hafellia is included.     

Coordination of leaf development via regulation of KNOX1 genes

Class I KNOTTED1-LIKE HOMEOBOX (KNOX1) genes are expressed in the shoot apical meristem (SAM) to effect its formation and maintenance. KNOX1 genes are also involved in leaf shape control throughout angiosperm evolution. Leaves can be classified as either simple or compound, and KNOX1 expression patterns in leaf primordia are highly correlated with leaf shape; in most simple-leafed species, KNOX1 genes are expressed only in the SAM but not in leaf primordia, while in compound-leafed species they are expressed both in the SAM and leaf primordia. How can KNOX1 expression be maintained to a high degree in the SAM, but simultaneously be so variable in leaves? This dichotomy suggests that the processes of leaf and SAM development have been compartmentalized during evolution. Here, we introduce our findings regarding the regulation of expression of SHOOT MERISTEMLESS, a KNOX1 gene, together with a brief review of KNOX1 genes from an evolutionary viewpoint. We also present our findings regarding another aspect of KNOX1 regulation via a protein–protein interaction network involved in the natural variation in leaf shape. Both aspects of KNOX1 regulation could be utilized for fine-tuning leaf morphology during evolution without affecting the essential function of KNOX genes in the shoot.     

Electrostatic charging of an electrically insulated metal body streamlined by a plasma flow

Electrostatic charging of an electrically insulated metal body streamlined by a plasma flow is investigated theoretically. The physical processes occurring in the vicinity of the body are considered. The electric currents resulting in the charging or discharging of the body are determined. The electric charge Q(t), electric field E(t), and potential φ(t) of a metal sphere are estimated taking into account the adopted conditions and parameters of the problem. The physical phenomena that take place in the vicinity of a charged body after Q(t) reaches a certain threshold value are discussed. The obtained values of Q(t), E(t), and φ(t) are compared with the corresponding values for a body streamlined by an atmospheric air flow.