Phragmoplastins,the Trentepohliales,and the Evolution of the Cytokinesis in Green Plants

Representatives of the monophyletic Trentepohliales are widely distributed in the tropics, subtropics, and temperate regions worldwide. They grow in soil, or are epilithic, epiphytic or endophytic. The family comprises approximately 70 species placed in at least four genera (Trentepohlia, Cephaleuros, Phycopeltis and Stomatochroon), with Trentepohlia sensu lato (including Printzina and Physolinum) accounting for half of the species in this family. PCR amplification and sequencing of the 18 SSU rDNA of 18 isolates of the Trentepohliaceae were used to assess the monophyly of the genus Cephaleuros and to determine the phylogenetic relationships among species of Trentepohlia sensu lato. Distance, Parsimony, and Maximum Likelihood analyses indicate that Trentepohlia sensu lato is basal and includes two species recently transferred to Phycopeltis (P. umbrina) and Printzina (P. lagenifera). In contrast, Cephaleuros is a derived monophyletic clade. Analysis of isolates of C. virescens, from the USA, Taiwan, and South Africa indicate that this taxon may consist of different species sharing a convergent morphology. The results of this study have implications for the taxonomy of the genera.     

Potentially active copies of the gypsy retroelement are confined to the y chromosome of some strains of drosophila melanogaster possibly as the result of the female-specific effect of the flamenco gene

Gypsy is an endogenous retrovirus present in the genome of Drosophila melanogaster. This element is mobilized only in the progeny of females which contain active gypsy elements and which are homozygous for permissive alleles of a host gene called flamenco (flam). Some data strongly suggest that gypsy elements bearing a diagnostic HindIII site in the central region of the retrovirus body represent a subfamily that appears to be much more active than elements devoid of this site. We have taken advantage of this structural difference to assess by the Southern blotting technique the genomic distribution of active gypsy elements. In some of the laboratory Drosophila stocks tested, active gypsy elements were found to be restricted to the Y chromosome. Further analyses of 14 strains tested for the permissive vs. restrictive status of their flamenco alleles suggest that the presence of permissive alleles of flam in a stock tends to be associated with the confinement of active gypsy elements to the Y chromosome. This might be the result of the female-specific effect of flamenco on gypsy activity. Received: 13 June 1997 / Accepted: 27 August 1997     

Unravelling the structure and function of the petal appendages in the tribe Schwenckieae (Solanaceae)

• The tribe Schwenckieae (Solanaceae) is characterised by the presence of appendages on the corolla, a diagnostic trait for the group. These appendages constitute a median distal projection of the three‐lobed petal and occur in the genera Melananthus and Schwenckia but are absent in Heteranthia.
• We investigated the micromorphology and anatomical structure of the appendages and lateral petal lobes of Schwenckia americana (two varieties), S. angustifolia, S. curviflora and S. novaveneciana, and Melananthus fasciculatus. We also performed histochemical tests to determine if the appendages are involved in the production of volatiles, acting as a fragrance secretory structure (osmophore).
• The appendages have a uniseriate epidermis, whose cells store phenolics and lipids. The parenchyma is starch‐rich just prior to anthesis in all species studied. The sensory test and anatomical analyses identified scent‐secreting tissues, not only in the appendages, but also in the lateral petal lobes, whose cells are papillose with a sculptured surface. The α‐naphthol p‐phenylenediamine (NADI) reaction detected volatile (essential oils) compounds in S. americana var. americana and S. americana var. angustifolia.
• We demonstrated the secretory tissues and the production of lipids in the corolla appendages of Schwenckia and Melananthus, which indicate their osmogenic function and probable scent emission to attract pollinators.

     

Floral morphology and taxonomic relations among the genera of Amaranthaceae in the New World and the Hawaiian Islands

Twenty-three genera of Amaranthaceae occur in the New World. Two endemic genera occur in the Hawaiian Islands. Among the genera of the subfamily Amaranthoideae, Celosia, Cyathula and Achyranthes have their main distributions in the Old World; the two last-named genera are represented in the Americas only by widespread weeds. All the New World genera of the subfamily Gomphrenoideae are mainly or entirely restricted to this region. Characters of androecium and gynoecium are fundamental in the recognition of genera within the family. Androecia of different genera may be structurally and phylogenetically more similar than would appear from a cursory examination. It is suggested that the type of staminal tubes found in Pseudogomphrena and Froelichia can be derived from that in Alternanthera and Froelichiella by reduction of filament length and a fusion of pseudostaminodia with the filaments. The staminal tube in Gomphrena could result from a further decrease in distance between pseudostaminodia of the Pseudogomphrena type, and a deeper forking of the pseudostaminodia; each so-called apical filament lobe in Gomphrena would then be homologous with half a pseudostaminodium in Pseudogomphrena. Much of the variation in the androecia of these and other genera, as well as within genera such as Pfaffia, can be explained as the combined results of coalescence and splitting-up tendencies. Splitting up of staminal tubes may not necessarily take place along the borders of phylogenetically original filaments and pseudostaminodia. The Amaranthus-type of pollen is found in the majority of genera of the subfamily Amaranthoideae, but also in the Chenopodiaceae. A group of genera within the subfamily Gomphrenoideae also has pollen very similar to, or identical with, this type. Most genera of the subfamily Gomphrenoideae have pollen of the Gomphrena-type. Pseudoplantago has unilocular (at anthesis) anthers, a characteristic of the subfamily Gomphrenoideae, but floral structure as well as pollen morphology connect the genus to a group of genera within the Amaranthoideae, subtribe Achyranthinae. The combination of subcuboidal shape and opercula with radially arranged hooked protuberances, makes the pollen of Pseudoplantago unique among the angiosperms studied so far. Floral morphology and palynological characteristics indicate a close relationship between Pfaffia and Alternanthera. Both genera, as currently accepted, are relatively homogeneous from pollen morphological points of view. There are no correlations between pollen morphology and the variation in the androecium in Pfaffia, nor would pollen structure support recognition of Hebanthe as a distinct genus. Woehleria and Irenella may be derived from, or be of the same origin as, Dicraurus and Iresine. All four genera are placed in the subfamily Gomphrenoideae because of the bisporangiate anthers, but their pollen structure is very close to, or identical with, that of the Amaranthus-type. Pseudogomphrena combines characteristics of Gomphrena and Pfaffia.     

Non-Circadian Periodicity in the Duration of the Cell Cycle and the G1 Phase in the Hindlimb Epidermis of the Anuran Tadpole,Rana Pipiens

Using the percentage labeled mitoses method, seven cell cycle determinations were initiated at 6-hr intervals over a 36-hr span in order to see if the cell cycle in the tadpole hindlimb epidermis varied with time or showed rhythmicity. There was a pattern of two long cell cycles followed by a shorter one. Total cell cycle length (Tc) and the length of the G₁ phase plus one-half of the mitotic time (TG₁+½M) fluctuated the most, although only TG₁+½M varied significantly with the Chi-square test. The proportion of TC spent in each phase was also calculated. Only TG₁+½M/Tc had statistically significant fluctuations with time.

Rhythmicity was analyzed by a computer program using the method of least squares for cosine curve fitting. Statistically significant ultradian rhythms of 18.4 hr in TC, 18.5 hr in TG₁+½M and 18.6 hr in TG₁+½M/TC and the length of the DNA synthetic phase/total cell cycle length (TS/TC) were found. Circadian rhythmicity was not observed. The acrophases of the ultradian rhythms of TC and TG₁+½M coincided, suggesting that the rhythm of TC was due mainly to variation in TG₁+½M. In the absence of significant variation in TS, the longest phase of the cell cycle, whenever G₁+½M was short, TS/TC increased, so that the 18.6 hr rhythm in TS/TC was also a result of the periodicity in TG₁+½M.     

On the Structure of the Avian Maculae

The maculae of the labyrinths of several avian species were examined. The striola of the macula utriculi and lagenae is tri-zonal, consisting of two zones of hair cells type I (HC I) located on each side of a middle zone of hair cells type II (HC II). An exception is the mute swan, in which the macula utriculi has a striola consisting of one broad zone of HC I. The macula sacculi is, in its central part, mainly consisting of HC I, and the striola does not have a tri-zonal structure. The hair cells in the macula utriculi are polarized with their kinociliar end oriented towards the striola, while in the macula sacculi and lagenae they are oriented away from this dividing line. A varying number, from 1 to 12, of HC I are enclosed within the same nerve chalice. The macula sacculi seems to contain chalices with slightly more HC I than the two other maculae do.     

Exploring the effect of the Cardinium endosymbiont on spiders

Spiders have recently emerged as important diversity hot spots for endosymbiotic bacteria, but the consequences of these symbiotic interactions are largely unknown. In this article, we examined the evolutionary history and effect of the intracellular bacterium Cardinium hertigii in the marbled cellar spider Holocnemus pluchei. We showed that Cardinium infection is primarily transmitted in spider populations maternally via egg cytoplasm, with 100% of the progeny from infected mothers being also infected. Examination of a co‐inherited marker, mitochondrial DNA (mtDNA), revealed that Cardinium infection is associated with a wide diversity of mtDNA haplotypes, showing that the interaction between Cardinium and H. pluchei has a long‐term evolutionary dimension and that horizontal transmission among individuals could also occur. Although Cardinium is well known to exert sex ratio distortion or cytoplasmic incompatibility in various arthropod hosts, we show, however, that Cardinium does not interact with the reproductive biology of H. pluchei. A field survey shows a clear geographical structuring of Cardinium infection, with a marked gradual variation of infection frequencies from ca. 0.80 to 0. We discuss different mechanistic and evolutionary explanations for these results as well as their consequences for spider phenotypes. Notably, we suggest that Cardinium can either behave as a neutral cytoplasmic element within H. pluchei or exhibit a context‐dependent effect, depending on the environmental conditions.     

Catalase overexpression reduces the germination time and increases the pathogenicity of the fungus Metarhizium anisopliae

Catalases and peroxidases are the most important enzymes that degrade hydrogen peroxide into water and oxygen. These enzymes and superoxide dismutase are the first lines of cell defense against reactive oxygen species. Metarhizium anisopliae displays an increase in catalase–peroxidase activity during germination and growth. To determine the importance of catalase during the invasion process of M. anisopliae, we isolated the cat1 gene. cat1 cDNA expression in Escherichia coli and the subsequent purification of the protein confirmed that the cat1 gene codes for a monofunctional catalase. Expression analysis of this gene by RT-PCR from RNA isolated from fungus grown in liquid cultures showed a decrease in the expression level of the cat1 gene during germination and an increase during mycelium growth. The expression of this gene in the fungus during the infection process of the larvae of Plutella xylostella also showed a significant increase during invasive growth. Transgenic strains overexpressing the cat1 gene had twice the catalase activity of the wild-type strain. This increase in catalase activity was accompanied by a higher level of resistance to exogenous hydrogen peroxide and a reduction in the germination time. This improvement was also observed during the infection of P. xylostella larvae. M. anisopliae transgenic strains overexpressing the cat1 gene grew and spread faster in the soft tissue of the insect, reducing the time to death of the insect by 25% and the dose required to kill 50% of the population 14-fold.     

A new Illumina MiSeq high-throughput sequencing-based method for evaluating the composition of the Bacteroides community in the intestine using the rpsD gene sequence

Bacteroides is a bacterial genus that is known to closely interact with the host. The potential role of this genus is associated with its ecological status and distribution in the intestine. However, the current 16S V3–V4 region sequencing method can only detect the abundance of this genus, revealing a need for a novel sequencing method that can elucidate the composition of Bacteroides in the human gut microbiota. In this study, a core gene, rpsD, was selected as a template for the design of a Bacteroides-specific primer set. We used this primer set to develop a novel assay based on the Illumina MiSeq sequencing platform that enabled an accurate assessment of the Bacteroides compositions in complex samples. Known amounts of genomic DNA from 10 Bacteroides species were mixed with a complex sample and used to evaluate the performance and detection limit of our assay. The results were highly consistent with those of direct sequencing with a low Bacteroides DNA detection threshold (0.01 ng), supporting the reliability of our assay. In addition, the assay could detect all the known Bacteroides species within the faecal sample. In summary, we provide a sensitive and specific approach to determining the Bacteroides species in complex samples.     

Nomenclatural remarks on the chasmophytic vegetation of the Centaureo-Campanuletalia

The thermophilous chasmophytic vegetation on limestone of the Adriatic Region has been arranged in the endemic order Centaureo-Campanuletalia (class Asplenietea trichomanis). The distribution range of the order covers a large area around the Adriatic Sea – from the south and north east of Italy to Slovenia, Croatia, Bosnia i Hercegovina, Montenegro and Albania. The Centaureo-Campanuletalia or its subordinated syntaxa are quoted in the main syntaxonomic synopses of the Region as well as in technical reports. The critical analysis of the nomenclature of the order, based on the International Code of Phytosociological Nomenclature (ICPN), showed many invalid or incorrect names while it is evident that the usage of correct names in scientific literature is crucial, both for the advances of syntaxonomic knowledge and their application for practical purposes. This paper presents a revision of the nomenclature for the Centaureo-Campanuletalia and related syntaxa in order to stabilize this nomenclature at least at alliance level. As a result, three syntaxa were validated (Centaureo dalmaticae-Campanuletalia pyramidalis, Centaureo cuspidatae-Portenschlagiellion ramosissimae, Inulo verbascifoliae-Centaureetum cuspidatae) and five others were lectotypified.     

Simulation of the dynamics in the Baker's yeast process

Simulation of the dynamics in a fed batch process for production of Baker's yeast is discussed and applied. Experimental evidences are presented for a model of the energy metabolism. The model involves the concept of a maximum respiratory capacity of the cell. If the sugar concentration is increased above a critical value, corresponding to a critical rate of glycolysis and a maximum rate of respiration, then all additional sugar consumed at higher sugar concentrations is converted into ethanol.In a fed batch process with constant sugar feed the sugar concentration declines slowly. If ethanol is present when the sugar concentration declines below the critical value of 110 mg/dm³ fructose +glucose the metabolism switches rapidly into combined oxidation of sugar and ethanol. Thus, no diauxic growth is involved under process conditions. The rate of ethanol consumption is determined by the free capacity of respiration under these conditions. The invertase activity of the cells was found to be so high that mainly fructose and glucose were present in the medium, typically in the concentration range around 100 mg/dm³. These components are consumed at the same rate but with fructose at a higher concentration, indicating a higher K _s for fructose consumption.The model was used in simulation experiments to demonstrate the dynamics of the Baker's yeast process and the influence of different process conditions.List of Symbols DOT % air sat dissolved oxygen tension - F dm³/h rate of inlet medium flow - H kg/(dm³ % air sat.) oxygen solubility - K kg/m³ saturation constant specified by index - K _L a 1/h volumetric oxygen transfer coefficient - m g/(g · h) maintenance coefficient specified by index - P kg/(m³ · h) mean productivity of biomass in the process - q g/(g · h) specific consumption or production rate - S kg/m³ concentration of sugar in reactor - S ₀ kg/m³ concentration of inlet medium sugar medium t h process time - V dm³ medium volume - X kg/m³ concentration of biomass - Y g/g yield coefficient specified by index - 1/h specific growth rate Index aa anaerobic condition - c critical value - e ethanol - ec ethanol consumption - ep ethanol production - max maximum value - o oxygen - oe oxygen for growth on ethanol - os oxygen for growth on sugar - s sugar - x biomass     

A contribution to the knowledge of the anostracan fauna of Iran

We report the finding of three anostracan species, Chirocephalus skorikowi Daday, 1913, Branchinecta orientalis Sars, 1901 and Branchinella spinosa. Milne-Edwards, 1840 in different localities in northwestern Iran. C. skorikowi was recorded in a lake at an elevation of 2400 m, whereas B. orientalis was found in a pond at 1280 m a.s.l. Co-existing B. spinosa and B. orientalis were collected in a pool close to the town of Tabriz, formerly indicated by Brehm (1954) as Estakr Chah, presently named EalGoli. Unlike Brehm (1954), we did not find Streptocephalus in the area of Tabriz.     

A glimpse into the past and predictions for the future: the molecular evolution of the tuberculosis agent

Recent advances in genomics and molecular biology are providing an excellent opportunity to get a glimpse into the past, to examine the present, and to predict the future evolution of pathogenic mycobacteria, and in particular that of Mycobacterium tuberculosis, the agent of human tuberculosis. The recent availability of genome sequences of several Mycobacterium canettii strains, representing evolutionary early‐branching tubercle bacilli, has allowed the genomic and molecular features of the putative ancestor of the M. tuberculosis complex (MTBC) to be reconstituted. Analyses have identified extensive lateral gene transfer and recombination events in M. canettii and/or the MTBC, leading to suggestions of a past environmental reservoir where the ancestor(s) of the tubercle bacilli might have adapted to an intracellular lifestyle. The daily increases in M. tuberculosis genome data and the remaining urgent Public Health problem of tuberculosis make it more important than ever to try and understand the origins and the future evolution of the MTBC. Here we critically discuss a series of questions on gene‐loss, acquisition, recombination, mutation and conservation that have recently arisen and which are key to better understand the outstanding evolutionary success of one of the most widespread and most deadly bacterial pathogens in the history of humankind.     

Involvement of a gene of the chl E locus in the regulation of the nitrate reductase operon

Summary A strain of E. coli carrying a Mudl insertion leading to chlorate resistance was found to lack nitrate reductase and formate dehydrogenase activities, but to synthesize b-type cytochrome constitutively. Introduction of this insertion mutation into a strain bearing a fusion between the nitrate reductase operon (chl C, chl I) and the lac structural genes resulted in the constitutive expression of the lac genes of this last fusion. Identical results were found when the Mudl was eliminated promoting a deletion in the original insertion site. This mutation was located midway between gal and aro A, at the chl E locus. Study of a chl E strain already described revealed similar behaviour. Absence of nitrate reductase activity in these strains which constitutively express the structural genes of the nitrate reductase operon was tentatively attributed to the simultaneous lack of a cofactor of the nitrate reductase terminal enzyme, possibly cofactor Mo-X, and of a repressor of the operon.     

On the measurement of shapes

We are here concerned with the functionf which assigns to each pointP of an object the numberf(P) which is the shortest distance fromP to the border. This function appears in various guises in diverse biological studies. The functionf(P) is itself a measure of shape—or more precisely, an infinite set of measures, one for each point (and hence, in view of its geometric definition, usually in a form inconvenient for use). Thus in this paper we sought a reasonable representative of this infinite set of measures, namely themean of the numbersf(P) asP ranges over all points of the entity. Computability studies are developed for various classes of shapes. For example, (1) the mean for a lamina bounded by a polygon circumscribable about a circle of radiusr isr/3; (2) the mean for a domain bounded by a polyhedron circumscribable about a sphere of radiusr isr/4. The transition from pointwise to piecewisef(P), especially in the non-convex case, requires working with inequalities.     

A comparative study of the epidermis of the common carp and the three Indian major carp

A comparative study has been made of the mucogenic epidermis of the common carp, Cyprinus carpio var. communis, and the three Indian major carps, Catla catla, Labeo rohita and Cirrhina mrigala: on the basis of epidermis structural organization, these species are easily differentiated. The epithelial cells in the superficial layer, as in most fishes, show secretory activity, evidenced by positive histochemical reactions, which is high in C. carpio var. communis, moderate in C. catla and low in L. rohita and C. mrigala. The epithelial cells in the underlying two or three layers also give positive reactions, though their intensity is relatively weak. The mucous cells in C. carpio var. communis are distributed in large numbers arranged in several superimposed layers in the outer regions of the epidermis, whereas in C. catla they are fewer in number and are widely separated in the surface layers as well as in the deeper layers of the epidermis; in both species the mucous cells appear rounded, large, and open on the surface by wide pores. In contrast, in L. rohita and C. mrigala the mucous cells are smaller, restricted mainly to the superficial layer, close together in a single row, and open on the surface by narrow pores. The overall density of mucous cells in L. rohita and C. mrigala, as in C. catla, is much lower than in C. carpio var. communis. In the epidermis of C. carpio var. communis there are a large number of mucous cells, and the few club cells are restricted to the deeper layers. In contrast, in the epidermis of the three Indian major carp the overall density of the mucous cells is much lower and the club cells are very numerous. It is suggested that the high density of club cells compensates an overall low density of mucous cells as an adaptation for an effective defence mechanism. Increased mucus production in the epidermis of C. carpio var. communis, as evidenced by a large number of mucous cells in outer regions and high secretory activity of superficial layer epithelial cells, is associated with increased precipitation of mud held in suspension, needed as an adaptation to the species’peculiar bottom-scooping habits. The varied density of the taste buds in the epidermis of the four carp is associated with their feeding habits.