Homeotic gene function in the muscles of Drosophila larvae

The segmental musculature of Drosophila melanogaster larvae consists of 24-30 muscles per segment. Unique patterns of muscles are found in the three thoracic segments and the first and last abdominal segments; the remaining abdominal segments share the same pattern. Mutations in Ultrabithorax (Ubx) cause partial transformation of the muscle pattern of larval abdominal segments towards metathorax. The muscles of the thorax are not affected. In the first two abdominal segments the changes include the loss of at least 11 `abdominal' muscles and the gain of 11 `thoracic' muscles. Less extensive transformations are seen in more posterior abdominal segments. Anterobithorax, bithorax, postbithorax and bithoraxoid mutations also induce transformations of the larval musculature. Each allelic group affects a domain that is a subset of the entire Ubx domain but these domains are not restricted to compartments or segments and may extend through as many as five segments. In the muscles the segmental distribution of Ubx antigen correlates with the segments affected by Ubx mutations. The different domains of Ubx in mesoderm and ectoderm argue that the segmental diversity of the muscle pattern is not simply induced by the overlying epidermis and that Ubx function in the mesoderm is required for the correct development of abdominal segments.     

Meristoderes gen. nov., a new kinorhynch genus, with the description of two new species and their implications for echinoderid phylogeny (Kinorhyncha: Cyclorhagida, Echinoderidae)

A new kinorhynch genus, Meristoderes gen. nov., and two new species from Spain and the Solomon Islands, respectively, are described. The new genus is distinguished from all other genera by the first segment consisting of a closed cuticular ring, and the second segment having partial tergosternal junctions, and a superficial midventral fold. This is a new cuticular configuration that may shed light into the phylogenetic relationships of echinoderid kinorhynchs. Meristoderes macracanthus gen. et sp. nov. from the Mediterranean coast of Spain is recognised by the presence of middorsal spines on segments 4, 6 and 8, ventrolateral tubules on segment 2, lateroventral tubules on segment 5, lateroventral spines on segments 6-9, lateral accessory tubules on segment 8, one pair of laterodorsal tubules on segment 10. Meristoderes galatheae sp. nov. from the Solomon Islands is recognized by having a middorsal spine on segment 4 only, ventrolateral tubules on segment 2, lateroventral tubules on segment 5, lateroventral spines on segments 6-9, lateral accessory tubules on segment 8 and subdorsal tubules on segment 10. Both species have a pattern of paraventral perforation site clusters on segments 3-9, with conspicuously long bracteate hairs from the posteriormost perforations sites on the segments 3-7 and 3-6, respectively.The new genus Meristoderes gen. nov. is included into the family Echinoderidae Bütschli, 1876 and appears closely related with the genera Cephalorhyncha Adrianov, 1999 and Echinoderes Claparède, 1863. The new information it provides is discussed to clarify the internal phylogeny of Echinoderidae. The terminology for cuticular characters in the overlapping area between consecutive segments is also standardized.     

The segmentation cascade in the centipede Strigamia maritima: involvement of the Notch pathway and pair-rule gene homologues

The centipede Strigamia maritima forms all of its segments during embryogenesis. Trunk segments form sequentially from an apparently undifferentiated disk of cells at the posterior of the germ band. We have previously described periodic patterns of gene expression in this posterior disc that precede overt differentiation of segments, and suggested that a segmentation oscillator may be operating in the posterior disc. We now show that genes of the Notch signalling pathway, including the ligand Delta, and homologues of the Drosophila pair-rule genes even-skipped and hairy, show periodic expression in the posterior disc, consistent with their involvement in, or regulation by, such an oscillator. These genes are expressed in a pattern of apparently expanding concentric rings around the proctodeum, which become stripes at the base of the germ band where segments are emerging. In this transition zone, these primary stripes define a double segment periodicity: segmental stripes of engrailed expression, which mark the posterior of each segment, arise at two different phases of the primary pattern. Delta and even-skipped are also activated in secondary stripes that intercalate between primary stripes in this region, further defining the single segment repeat. These data, together with observations that Notch mediated signalling is required for segment pattern formation in other arthropods, suggest that the ancestral arthropod segmentation cascade may have involved a segmentation oscillator that utilised Notch signalling.     

中国梳蓟马属一新种（缨翅目：蓟马科）

记述中国梳蓟马属1新种:Ctenothrips dissimilis sp.nov.。该新种触角7节、腹部网状刻纹较浅,可明显区别于本属内其它种;雄虫和C.niger很相似,但C.niger腹部III-IV节腹板腺域为短圆形,该新种腺域为长椭圆形,同时触角节数和颜色也不同。模式标本保存于西北农林科技大学昆虫博物馆。     

Ultrastructure of Wax-Producing Structures on the Integument of the Melaleuca Psyllid Boreioglycaspis melaleucae (Hemiptera: Psyllidae), with Honeydew Excretion Behavior in Males and Females

The melaleuca psyllid, Boreioglycaspis melaleucae (Hemiptera: Psyllidae), was introduced to Florida as a biological control agent against Melaleuca quinquenervia, an invasive evergreen tree that has invaded large areas of Florida Everglades. Colonies of B. melaleucae nymphs are normally covered by white waxy secretions, and nymphs of various instars produce long bundles of white waxy filaments extending laterally and posteriorly from their abdomen. Scanning electron microscopy of ‘naturally waxed’ and ‘dewaxed’ nymphs (cleaned from wax) revealed two types of wax pore plates located dorsally and laterally on the integument of posterior abdominal segments starting with the 4th segment. Type-1 wax pore plates, with raised rim, peripheral groove, slits and pits, produce long ribbons and filaments of waxy secretions that are wound together forming long wax bundles, whereas type-2 wax pore plates, with slits only, produce shorter wax curls. Additionally, in both nymphs and adult females, the circumanal ring contained ornate rows of wax pores that produce wax filaments covering their honeydew excretions. Video recordings with stereomicroscopy showed that adult females produce whitish honeydew balls, powerfully propelled away from their body, probably to get these sticky excretions away from their eggs and newly hatched nymphs. Adult males, however, produce clear droplets of honeydew immediately behind them, simply by bending the posterior end of the abdomen downward. The possible role(s) of waxy secretions by nymphs and adults of B. melaleucae in reducing contamination of their colonies with honeydew, among other possibilities, are discussed.     

A redescription of Cumoniscus Bonnier, 1903 (Crustacea: Tantulocarida) from a cumacean host in the Bay of Biscay

Cumoniscus kruppi Bonnier, the only tantulocarid known from a cumacean host, is redescribed from a tantulus larva collected from the Bay of Biscay. The host is a male leuconid cumacean. This genus is placed in the family Deoterthridae, and can be distinguished from other genera by the pore pattern on the cephalic shield, the reduced setae on the sixth legs and the presence of tiny curved spinules on the endopod of thoracopods 2 to 5.     

NanC Crystal Structure, a Model for Outer-Membrane Channels of the Acidic Sugar-Specific KdgM Porin Family

Sialic acids are acidic sugars present mostly on vertebrate cell surfaces, which can be metabolized by bacteria and act as an inflammation signal. N-Acetylneuraminic acid, the most abundant sialic acid, can enter into Escherichia coli K12 through NanC, an N-acetylneuraminic acid-inducible outer-membrane channel. With its 215 residues, NanC belongs to the family of small monomeric KdgM-related porins. KdgM homologues are found in gammaproteobacteria, including major plant and human pathogens, and together they define a large family of putative acidic sugar/oligosaccharide transporters, which are as yet poorly characterized. Here, we present the first high-resolution structure of a KdgM family member. NanC folds into a 28-Å-high, 12-stranded β-barrel, resembling the β-domain of autotransporter NalP and defining an open pore with an average radius of 3.3 Å. The channel is lined by two strings of basic residues facing each other across the pore, a feature that appears largely conserved within the KdgM family and is likely to facilitate the diffusion of acidic oligosaccharides.     

Redescription of Folsomia loftyensis Womersley with notes on the sensillary arrangement of the genital segment in the genus (Collembola: Isotomidae)

Folsomia loftyensis Womersley is redescribed based on material from South Australia, Victoria and Queensland. The species exhibits, for the genus, an unusual sensillary pattern on the posterior abdominal segments. The arrangement and form of the five sensilla on the genital segment of most described species of Folsomia from the Palearctic are analysed and species divided into groups based on these characters. Several different lineages are detected.     

A new genus of Cletopsyllidae (Copepoda,Harpacticoida) from Gulf of Mexico

A new genus and new species of the family Cletopsyllidae Huys & Willems, 1989 from deep-sea sediment in the Gulf of Mexico, are reported and fully described and illustrated. The new genus Pentacletopsyllus (type species: P. montagni sp. n.) can be distinguished from the four known genera of the family by antennule segmentation, length ratio of first and second endopodal segments of P1, and armature pattern on P5 exopod. It also differs from its sister genera by the rostrum being bifid at the tip, third segment of the female antennule having a smooth posterior margin, the baseoendopod of P5 with biarticulate outer setophore bearing basal seta, and female caudal rami without lobate expansion. A revised key to species of the family Cletopsyllidae Huys & Willems, 1989 is provided.     

Morphogeographic variations in the genusMesopodopsis Czerniavsky with descriptions of three new species (Crustacea,Mysidacea)

Most of the exceptional morphological features of the genusMesopodopsis are shared withNanomysis, Diamysis, andLimnomysis in a mosaic-like pattern. This group, comprising euryhaline species from fresh-to metahaline waters, has its centre of recent species richness in the Mediterranean to Ponto-Caspian region. Within the genus one may distinguish two morphogeographic groups, Euro-African species with a spine below the statocyst, and Indo-Australasian species without this spine. Detailed study from the entire distribution range indicates thatM. slabberi (van Beneden) should be split into 4 species: the nominal form from the NE-Atlantic, Mediterranean, and Black Sea, with 5–8 segments on the tarsus of the fourth thoracic endopod;M. aegyptia n.sp., widely distributed in the Mediterranean, with 7–9 segments on this tarsus as well as dimorphic setation patterns on the eighth tarsus;M. tropicalis n.sp. from equatorial W-Africa with 5–6 segments and dimorphic setation patterns on the mandibular palp; andM. wooldridgei n.sp. from South African waters with 9–12 segments on the tarsal joint of the fourth thoracic appendage, respectively. A key to the seven known species of the genus is given.     

Regeneration of the segment boundary in Oncopeltus

The segment boundary of Oncopeltus is a compartment border. It is also an element in the pattern of the abdomen, being marked by a groove in the surface of the cuticle and an abrupt change in the pigmentation of the cells. If the segment boundary is either burnt or extirpated, the surviving cells of the two neighbouring segments migrate into the wounded area and form a new segment boundary where they confront each other. Grafting experiments with genetically marked cells demonstrate that a boundary is regenerated wherever cells from remote locations in the anteroposterior axis of any segment are apposed; thus anterior and posterior cells from the same segment form an ectopic boundary when brought together, while cells from equivalent positions in two segments heal together without forming a boundary. We consider the segment boundary to be an element in a pattern which reiterates down the longitudinal axis of the body—whenever cells from different positions in this pattern are brought together intercalation occurs. The intercalation can either be within a segment (no boundary forms) or between segments (a boundary forms). The route of intercalation appears to be the shortest available, so that when the apposed cells are more than half a segment length apart a new boundary forms.     

Sequential packaging of RNA genomic segments during the assembly of Bluetongue virus

Bluetongue virus (BTV), a member of the Orbivirus genus within the Reoviridae family, has a genome of 10 double-stranded RNA segments, with three distinct size classes. Although the packaging of the viral genome is evidently highly specific such that every virus particle contains a set of 10 RNA segments, the order and mechanism of packaging are not understood. In this study we have combined the use of a cell-free in vitro assembly system with a novel RNA–RNA interaction assay to investigate the mechanism of single-stranded (ss) RNAs packaging during nascent capsid assembly. Exclusion of single or multiple ssRNA segments in the packaging reaction or their addition in different order significantly altered the outcome and suggested a particular role for the smallest segment, S10. Our data suggests that genome packaging probably initiates with the smallest segment which triggers RNA–RNA interaction with other smaller segments forming a complex network. Subsequently, the medium to larger size ssRNAs are recruited until the complete genome is packaging into the capsid. The untranslated regions of the smallest RNA segment, S10, is critical for the instigation of this process. We suggest that the selective packaging observed in BTV may also apply to other members of the Reoviridae family.     

Alanine Scanning of the S6 Segment Reveals a Unique and cAMP-sensitive Association between the Pore and Voltage-dependent Opening in HCN Channels

Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels resemble Shaker K⁺ channels in structure and function. In both, changes in membrane voltage produce directionally similar movement of positively charged residues in the voltage sensor to alter the pore structure at the intracellular side and gate ion flow. However, HCNs open when hyperpolarized, whereas Shaker opens when depolarized. Thus, electromechanical coupling between the voltage sensor and gate is opposite. A key determinant of this coupling is the intrinsic stability of the pore. In Shaker, an alanine/valine scan of residues across the pore, by single point mutation, showed that most mutations made the channel easier to open and steepened the response of the channel to changes in voltage. Because most mutations likely destabilize protein packing, the Shaker pore is most stable when closed, and the voltage sensor works to open it. In HCN channels, the pore energetics and vector of work by the voltage sensor are unknown. Accordingly, we performed a 22-residue alanine/valine scan of the distal pore of the HCN2 isoform and show that the effects of mutations on channel opening and on the steepness of the response of the channel to voltage are mixed and smaller than those in Shaker. These data imply that the stabilities of the open and closed pore are similar, the voltage sensor must apply force to close the pore, and the interactions between the pore and voltage sensor are weak. Moreover, cAMP binding to the channel heightens the effects of the mutations, indicating stronger interactions between the pore and voltage sensor, and tips the energetic balance toward a more stable open state.Hyperpolarization-activated cyclic nucleotide-modulated (HCN)4 channels are similar in structure and function to Shaker K⁺ channels (1–3). As in Shaker, HCN channels are comprised of four subunits, which each consist of six predicted membrane-spanning segments (S1–S6). The S1–S4 segments form the voltage-sensing domain, and the S5 and S6 segments, the pore-forming domain. The S4 segment in both channels contains positive charges that move similarly in response to changes in membrane voltage (4–6), to then alter the pore structure at the intracellular side of the S6 segment; this region functions as a voltage-controlled gate to cation flow (7–10). Despite these similarities, HCN channels are opened by hyperpolarization of the membrane potential, whereas Shaker channels open in response to depolarization. Thus, the electromechanical coupling between the voltage sensor and the gate is reversed in these two channels.A key determinant of this coupling is the intrinsic stability of the closed and open conformations of the pore. In Shaker channels, it has been proposed that the pore is intrinsically most stable when closed and that the voltage sensor works to open the pore during depolarization (11, 12). Results from an alanine/valine scan of residues across the entire Shaker pore, by single point mutation, showed that most mutations made the channel easier to open and steepened the response of the channel to changes in voltage. It was argued that, because most mutations likely destabilize protein packing, the closed conformation must be the stable state; this is consistent with the observed crystal structures of Shaker-related channels KcsA and MthK, in the closed and open states, respectively, wherein more optimally and tightly packed helices were seen in the closed conformation (13–15).Because of presumed shared architecture of the gate between HCN and Shaker channels, HCN channels might also be most stable when closed, and thus the voltage sensor would work to open the pore upon hyperpolarization. To test this hypothesis, we performed an alanine/valine scan of the C-terminal 22 amino acids of the S6 segment in HCN2, used as a prototype, and examined pore energetics as described previously in Shaker (11). Choice of this region for mutation was based on: 1) in Shaker, the corresponding region harbors one of two clusters of gating-sensitive residues and 2) it contains the voltage-controlled gate. Surprisingly, the effects of the mutations on channel opening and on the steepness of the channel''s response to voltage are mixed and smaller than those in Shaker. These findings imply that, in HCN2, the stabilities of the open and closed pore are similar, the interactions between the pore and voltage sensor, both structural and functional, are weaker than in Shaker, and that the voltage sensor must apply force to the pore to close it. Thus, Shaker is closed and HCN2 is open in the absence of input from the voltage sensor. Moreover, cAMP binding to the HCN2 channel heightens the effects of the mutations, indicating stronger interactions between the pore and voltage sensor, and tips the energetic balance toward a more stable open state.     

Pattern formation in the egg of the leafhopper Euscelis plebejus Fall. (Homoptera): Developmental capacities of fragments isolated from the polar egg regions

The egg of the leafhopper Euscelis plebejus has been separated into three fragments [for nomenclature, see Sander, K. (1976). Advan. Insect Physiol.12, 125–238] by two constrictions in order to exclude the middle egg part from possible terminal influences on pattern specification. Middle fragments of freshly laid eggs (two pronuclei or one nucleus) differentiate middle segments of the embryonic pattern. The segment composition of those partial patterns varies with the position of the two constrictions. Eggs subdivided at later stages of development produce similar partial patterns in the middle fragment, but with more segments. The mode of segment expression in single and double fragmented eggs is compatible with the assumption that the metameric pattern is differentiated by a sequence of short-range inductions rather than by an extensive gradient field.     

Structural position correlation analysis (SPCA) for protein family

Background

The proteins in a family, which perform the similar biological functions, may have very different amino acid composition, but they must share the similar 3D structures, and keep a stable central region. In the conservative structure region similar biological functions are performed by two or three catalytic residues with the collaboration of several functional residues at key positions. Communication signals are conducted in a position network, adjusting the biological functions in the protein family.

Methodology

A computational approach, namely structural position correlation analysis (SPCA), is developed to analyze the correlation relationship between structural segments (or positions). The basic hypothesis of SPCA is that in a protein family the structural conservation is more important than the sequence conservation, and the local structural changes may contain information of biology functional evolution. A standard protein P⁽⁰⁾ is defined in a protein family, which consists of the most-frequent amino acids and takes the average structure of the protein family. The foundational variables of SPCA is the structural position displacements between the standard protein P⁽⁰⁾ and individual proteins P_i of the family. The structural positions are organized as segments, which are the stable units in structural displacements of the protein family. The biological function differences of protein members are determined by the position structural displacements of individual protein P_i to the standard protein P⁽⁰⁾. Correlation analysis is used to analyze the communication network among segments.

Conclusions

The structural position correlation analysis (SPCA) is able to find the correlation relationship among the structural segments (or positions) in a protein family, which cannot be detected by the amino acid sequence and frequency-based methods. The functional communication network among the structural segments (or positions) in protein family, revealed by SPCA approach, well illustrate the distantly allosteric interactions, and contains valuable information for protein engineering study.     

A Tether for Woronin Body Inheritance Is Associated with Evolutionary Variation in Organelle Positioning

Eukaryotic organelles evolve to support the lifestyle of evolutionarily related organisms. In the fungi, filamentous Ascomycetes possess dense-core organelles called Woronin bodies (WBs). These organelles originate from peroxisomes and perform an adaptive function to seal septal pores in response to cellular wounding. Here, we identify Leashin, an organellar tether required for WB inheritance, and associate it with evolutionary variation in the subcellular pattern of WB distribution. In Neurospora, the leashin (lah) locus encodes two related adjacent genes. N-terminal sequences of LAH-1 bind WBs via the WB–specific membrane protein WSC, and C-terminal sequences are required for WB inheritance by cell cortex association. LAH-2 is localized to the hyphal apex and septal pore rim and plays a role in colonial growth. In most species, WBs are tethered directly to the pore rim, however, Neurospora and relatives have evolved a delocalized pattern of cortex association. Using a new method for the construction of chromosomally encoded fusion proteins, marker fusion tagging (MFT), we show that a LAH-1/LAH-2 fusion can reproduce the ancestral pattern in Neurospora. Our results identify the link between the WB and cell cortex and suggest that splitting of leashin played a key role in the adaptive evolution of organelle localization.     

Important Role of Asparagines in Coupling the Pore and Votage-Sensor Domain in Voltage-Gated Sodium Channels

Voltage-gated sodium (Na_V) channels contain an α-subunit incorporating the channel’s pore and gating machinery composed of four homologous domains (DI–DIV), with a pore domain formed by the S5 and S6 segments and a voltage-sensor domain formed by the S1–S4 segments. During a membrane depolarization movement, the S4s in the voltage-sensor domains exert downstream effects on the S6 segments to control ionic conductance through the pore domain. We used lidocaine, a local anesthetic and antiarrhythmic drug, to probe the role of conserved Asn residues in the S6s of DIII and DIV in Na_V1.5 and Na_V1.4. Previous studies have shown that lidocaine binding to the pore domain causes a decrease in the maximum gating (Q_max) charge of ∼38%, and three-fourths of this decrease results from the complete stabilization of DIII-S4 (contributing a 30% reduction in Q_max) and one-fourth is due to partial stabilization of DIV-S4 (a reduction of 8–10%). Even though substitutions for the Asn in DIV-S6 in Na_V1.5, N1764A and N1764C, produce little ionic current in transfected mammalian cells, they both express robust gating currents. Anthopleurin-A toxin, which inhibits movement of DIV-S4, still reduced Q_max by nearly 30%, a value similar to that observed in wild-type channels, in both N1764A and N1764C. By applying lidocaine and measuring the gating currents, we demonstrated that Asn residues in the S6s of DIII and DIV are important for coupling their pore domains to their voltage-sensor domains, and that Ala and Cys substitutions for Asn in both S6s result in uncoupling of the pore domains from their voltage-sensor domains. Similar observations were made for Na_V1.4, although substitutions for Asn in DIII-S6 showed somewhat less uncoupling.     

Molecular Cytogenetic Characterization of Multiple Intrachromosomal Rearrangements in Two Representatives of the Genus Turdus (Turdidae,Passeriformes)

Turdus rufiventris and Turdus albicollis, two songbirds belonging to the family Turdidae (Aves, Passeriformes) were studied by C-banding, 18S rDNA, as well as the use of whole chromosome probes derived from Gallus gallus (GGA) and Leucopternis albicollis (LAL). They showed very similar karyotypes, with 2n = 78 and the same pattern of distribution of heterochromatic blocks and hybridization patterns. However, the analysis of 18/28S rDNA has shown differences in the number of NOR-bearing chromosomes and ribosomal clusters. The hybridization pattern of GGA macrochromosomes was similar to the one found in songbirds studied by Fluorescent in situ hybridization, with fission of GGA 1 and GGA 4 chromosomes. In contrast, LAL chromosome paintings revealed a complex pattern of intrachromosomal rearrangements (paracentric and pericentric inversions) on chromosome 2, which corresponds to GGA1q. The first inversion changed the chromosomal morphology and the second and third inversions changed the order of chromosome segments. Karyotype analysis in Turdus revealed that this genus has derived characteristics in relation to the putative avian ancestral karyotype, highlighting the importance of using new tools for analysis of chromosomal evolution in birds, such as the probes derived from L. albicollis, which make it possible to identify intrachromosomal rearrangements not visible with the use of GGA chromosome painting solely.     

Trichodorus philipi n. sp. from South Africa,with Notes on Paratrichodorus lobatus and P. acutus

A new species in the family Trichodoridae, from the rhizosphere of native plants of the Cape Fynbos in the western Cape, Republic of South Africa, is described and illustrated. Trichodorus philipi n. sp. resembles T. cottieri Clark, 1963 and T. degans Allen, 1957, from which both sexes are distinguished by a shorter body and onchiostyle. The females differ by the more posterior position of excretory pore, presence of two pairs of lateral body pores, and shape and sclerotization of vulval-vaginal region in lateral view. Males differ by the more posterior position of excretory pore and ventromedian cervical papilla and length and shape of the spicules. Additional morphological details and morphometrics are given for Paratrichodorus lobatus (Colbran, 1965) Siddiqi, 1974 and P. acutus (Bird, 1967) Siddiqi, 1974.