The cumacean genus Iphinoe (Crustacea: Peracarida) from Italian waters and I. daphne n. sp. from the northwestern Adriatic Sea, Mediterranean

Records of the cumacean genus Iphinoe from Italian coasts are reported with relevant data on the habitat, morphology and geographical distribution of each species. Seven Iphinoe species from the Italian coasts were recorded and are presented here with their own distributional ranges; the description of a new species, Iphinoe daphne n. sp. is also given.                Our results extend the known distribution of some species to new areas of the Mediterranean Sea and suggest that the species Iphinoe adriatica Bâcescu, 1988 can be considered as a nomen dubium, while the presence of I. trispinosa along the Italian coast is doubtful.Finally, a dichotomous key for all Mediterranean Iphinoe species is provided.

Bottom-trawl catch composition in a highly polluted coastal area reveals multifaceted native biodiversity and complex communities of fouling organisms on litter discharge

Areas subjected to anthropogenic impacts are important to test the effect of stressors on local biota. We assessed with trawl net the composition and abundance of megafauna, litter, and litter-fouling communities in the soft bottoms of the National Interest Priority Site (NIPS) of Bagnoli-Coroglio (Gulf of Naples, Tyrrhenian Sea) at different depths. The megafauna accounted for 3444 specimens referred to 133 taxa (91 invertebrates and 42 fishes), for a biomass of ~102 kg and including species of wide ecological and commercial interest. Metrics of community structure yielded high values. The NIPS, hence, is characterized by a high biodiversity. Litter accounted for 3590 items, mostly in plastic and ranging between 10< × ≤20 cm, for a weight of ~260 kg, with values of 299.2 item/km² and 21.67 kg/km². The putative origin of most items was land-based (83.6%), whereas sea-based litter accounted for 16.4%. More than 50% of the litter items found showed colonization by invertebrates and/or molluscan egg masses. Marine benthic litter, thus, locally constitutes a complex issue since litter items hosted complex communities of fouling organisms. Future remediation procedures should take the resident NIPS biota into account and not disrupt the environmental balance of the area.

Macrofaunal biodiversity associated with different developmental phases of a threatened Mediterranean Sabellaria alveolata (Linnaeus, 1767) reef

Sabellaria alveolata is an ecosystem engineer species capable of building bioconstructions, playing a key functional role in the shallow coastal ecosystems. S. alveolata reefs perform several ecosystem services, such as hosting a rich fauna and producing structures able to provide coastal protection. Despite their ecological role, these bioconstructions have been poorly investigated in the Mediterranean Sea. In this study, the largest Mediterranean S. alveolata reef, located along the Latium coast, was recorded and an habitat mapping duly carried out. During a one-year study, the balance between reef status and associated fauna was investigated using a multidisciplinary approach, the different phases in the annual cycle of S. alveolata were detected and the reef's influence on the diversity of associated macrofauna was assessed. The retrograding phase was detected in September, due to the damages by trampling disturbance, while the growing phase began in March. The comparison with the fauna of the adjacent substrates was also performed, demonstrating that the reef supported a high diversity of associated fauna and qualifying the reef as a biodiversity hotspot. Aimed at improving knowledge of Mediterranean reefs, our study lays the basis for more effective management plans and protection strategies for the threatened biogenic habitats.

Aglaophenia octodonta (Cnidaria, Hydrozoa) and the Associated Microbial Community: a Cooperative Alliance?

Recently, genetic approaches have revealed a surprising bacterial world as well as a growing knowledge of the enormous distribution of animal-bacterial interactions. In the present study, the diversity of the microorganisms associated to the hydroid Aglaophenia octodonta was studied with epifluorescence, optical, and scanning electron microscopy. Small subunit ribosomal RNA gene sequencing with "universal" and taxon-specific primers allowed the assignment of the microalgae to Symbiodinium and the peritrich ciliates to Pseudovorticella, while the luminous vibrios were identified as Vibrio jasicida of the Harvey clade. To understand the possible relationships among Vibrio jasicida, Symbiodinium, A. octodonta, and Pseudovorticella, specific treatments were conducted in microcosm experiments, with the antibiotic ampicillin and other substances that interfere with bacterial and hydroid metabolism. Treatment of A. octodonta with ampicillin resulted in a decrease of bacterial luminescence followed by Pseudovorticella detachment and Symbiodinium expulsion and suggesting that these microorganisms form a "consortium" with beneficial metabolic interdependence. This hypothesis was reinforced by the evidence that low concentrations of hydrogen peroxide, which stimulate the bacterial oxidative metabolism and luminescence by releasing oxygen, were able to counteract the detrimental effect of ampicillin on the stability of the studied A. octodonta association. A model is proposed in which microalgae that release oxygen during photosynthesis are useful to luminous bacteria for their metabolism and for establishing/maintaining symbiosis leading to a close alliance and mutual benefit of the system A. octodonta-Vibrio jasicida-Pseudovorticella sp.-Symbiodinium sp.

Clarifying the taxonomic status of the alien species Branchiomma bairdi and Branchiomma boholense (Annelida: Sabellidae) using molecular and morphological evidence

This study was performed to analyse the genetic and morphological diversity of the sabellid annelid genus Branchiomma, with special emphasis on a taxon so far identified as Branchiomma bairdi. This species, originally described from Bermuda, has frequently been reported as an invader in the Mediterranean, the Atlantic and the Eastern Pacific, but recent observations have raised some taxonomic questions. Samples of this taxon were collected from five sites in the Mediterranean Sea, two sites in the original distribution area of B. bairdi in the Gulf of Mexico and four localities in the east Pacific and Atlantic Oceans where B. bairdi has been reported as invasive. The molecular results revealed a conspicuous genetic divergence (18.5% K2P) between the sampled Mediterranean populations and all the other ones that led to a re-evaluation of their morphological characters. The latter showed that the Mediterranean and extra-Mediterranean populations also differ in some discrete morphological and reproductive features. Consequently, the Mediterranean samples were re-designated as B. boholense, another non-indigenous species originally described from Philippines. Branchiomma bairdi and B. boholense differ in body size, development and shape of micro and macrostylodes, size of radiolar eyes and body pigmentation. Genetic diversity was high in B. boholense from the Mediterranean as well as in B. bairdi from the Gulf of Mexico, but low in B. bairdi populations outside their native range. The phylogenetic analysis revealed the presence of connections between the Mediterranean localities as well as between native and introduced B. bairdi populations that focus the attention on the Panama Canal as important passage for the introduction of the species from the Gulf of Mexico to the north-east Pacific Ocean.

Successional dynamics of marine fouling hydroids (Cnidaria: Hydrozoa) at a finfish aquaculture facility in the Mediterranean Sea

Aquaculture is increasing rapidly to meet global seafood demand. Some hydroid populations have been linked to mortality and health issues in finfish and shellfish, but their dynamics in and around aquaculture farms remain understudied. In the present work, two experiments, each with 36 panels, tested colonization (factors: depth, season of immersion) and succession (factors: depth, submersion duration) over one year. Hydroid surface cover was estimated for each species, and data were analyzed with multivariate techniques. The assemblage of hydrozoans was species-poor, although species richness, frequency and abundance increased with time, paralleling the overall increase in structural complexity of fouling assemblages. Submersion duration and season of immersion were particularly important in determining the species composition of the assemblages in the succession and colonization experiments, respectively. Production of water-borne propagules, including medusae, from the hydroids was observed from locally abundant colonies, among them the well-known fouling species Obelia dichotoma, potentially representing a nuisance for cultured fish through contact-driven envenomations and gill disorders. The results illustrate the potential importance of fouling hydroids and their medusae to the health of organisms in the aquaculture industry.

The Mediterranean non-indigenous ascidian Polyandrocarpa zorritensis: Microbiological accumulation capability and environmental implications

We investigated the bacterial accumulation and digestion capability of Polyandrocarpa zorritensis, a non-indigenous colonial ascidian originally described in Peru and later found in the Mediterranean. Microbiological analyses were carried out on homogenates from "unstarved" and "starved" ascidians and seawater from the same sampling site (Adriatic Sea, Italy). Culturable heterotrophic bacteria (22 °C), total culturable bacteria (37 °C) and vibrios abundances were determined on Marine Agar 2216, Plate Count Agar and TCBS Agar, respectively. Microbial pollution indicators were measured by the most probable number method. All the examined microbiological groups were accumulated by ascidians but differently digested. An interesting outcome is the capability of P. zorritensis to digest allochthonous microorganisms such as coliforms as well as culturable bacteria at 37 °C, counteracting the effects of microbial pollution. Thus, the potential exploitation of these filter feeders to restore polluted seawater should be taken into consideration in the management of this alien species.

Microbiological accumulation by the Mediterranean invasive alien species Branchiomma bairdi (Annelida, Sabellidae): potential tool for bioremediation

We examined the bacterial accumulation and digestion in the alien polychaete Branchiomma bairdi. Microbiological analyses were performed on worm homogenates from "unstarved" and "starved" individuals and on seawater from the same sampling site (Ionian Sea, Italy). Densities of culturable heterotrophic bacteria (22 °C), total culturable bacteria (37 °C) and vibrios were measured on Marine Agar 2216, Plate Count Agar and TCBS Agar, respectively. Microbial pollution indicators were determined by the most probable number method. B. bairdi was able to accumulate all the six considered microbiological groups which, however, differ in their resistance to digestion. B. bairdi results more efficient than the other two co-occurring sabellids in removing bacteria suggesting that it may counteract the effects of microbial pollution playing a potential role for in situ bioremediation. Thus a potential risk, such as the invasion of an alien species, could be transformed into a benefit with high potential commercial gain and economic feasibility.

Comparative toxicity and ecdysone receptor affinity of non-steroidal ecdysone agonists and 20-hydroxyecdysone in Chironomus tentans

Ecdysone agonists belonging to the bisacylhydrazine class of compounds are a new generation of insecticidal compounds that cause premature lethal molts in susceptible intoxicated insects. While two of the bisacylhydrazines (coded as RH-5992 and RH-2485) are predominantly toxic to lepidopteran pests, RH-5849, which has not been commercialized, has a broader spectrum of toxicity. We have carried out toxicity bioassays with last (4th) instar Chironomus tentans L. larvae, radioligand binding assays using bacterial fusion proteins of C. tentans ecdysone receptor and ultraspiracle (CtEcR, CtUSP), and C. tentans imaginal disc development assays to compare the relative potencies of the three bisacylhydrazine compounds as well as of 20-hydroxyecdysone (20E). In all three assays, the potency of the three bisacylhydrazines was in the order RH-2485>RH-5992>RH-5849. While in toxicity assays 20E was ineffective, most likely due to rapid metabolism, it was more potent than RH-5849 but less so than RH-5992 and RH-2485 in imaginal disc assays. In summary, we compared the potencies of the ecdysone agonists for C. tentans at three levels: whole organism, imaginal discs and the receptor level, and our results indicate that the increased toxicity of the non-steroidal ecdysone agonists for C. tentans has a high correlation to the affinity of these compounds for CtEcR/CtUSP bacterially expressed proteins. Our results, though, do not exclude reasons of metabolic stability of the compounds in C. tentans, which we have not investigated in this report.

Differential control of gene activity by isoforms A, B1 and B2 of the Drosophila ecdysone receptor

The steroid hormone ecdysone initiates molting and metamorphosis in Drosophila via a heterodimeric receptor consisting of EcR that binds hormone, and USP, a homolog of the vertebrate RXR receptor. EcR exists in three isoforms EcRA, EcRB1 and EcRB2 that are thought to direct specific physiological responses to ecdysone. These three isoforms differ only in their N-terminal A/B domain that implies that sequences responsible for the differential physiological effects lie within the A/B domains of the EcR isoforms. In the present study, we set out to determine the capability of the three isoforms and their A/B domains to control gene transcription. When full-length EcR plasmids were cotransfected into mammalian cells with a USP expressing and a cognate reporter plasmid, the three EcR isoforms showed striking differences in their ability to control gene transcription, both in the presence and in the absence of hormone. Furthermore, the A/B domains of EcRB1 and of EcRB2 when fused to the GAL4 DNA binding domain are sufficient to activate transcription of a reporter gene, in yeast as well as in mammalian cells. In contrast, a fusion construct containing the A/B domain of EcRA represses basal transcription of the reporter gene. All these findings emphasize the importance of the A/B domains of the three EcR isoforms for differentially controlling gene transcription. Furthermore, they provide evidence for the existence of an autonomous ligand-independent activation function (AF1) in the A/B domains of EcRB1 and EcRB2 and of an inhibitory function (IF) in the A/B domain of EcRA.

Developmental effects of a chimeric ultraspiracle gene derived from Drosophila and Chironomus

The ultraspiracle (usp) gene encodes a nuclear receptor that forms a heterodimer with the ecdysone receptor (EcR) to mediate transcriptional responses to the insect steroid hormone, 20-hydroxyecdysone (20HE). The responses ultimately elicit changes associated with molting and metamorphosis. Although Ultraspiracle (USP) is required at several developmental times, it is unclear whether USP plays stage-specific roles in Drosophila. A chimeric transgene (d/cusp), produced by replacing the ligand-binding domain (LBD) of Drosophila USP with the equivalent domain from another Diptera, Chironomus tentans, was tested for its ability to rescue Drosophila usp mutants from early larval lethality. A single copy of the d/cusp was sufficient to rescue transformants from several lines through larval development but they died suddenly during the late third instar. Additional doses of d/cusp were required to allow survival through the adult stage, but they did not restore a normal prepupal contraction. Thus, the arrest at the onset of metamorphosis apparently is caused by the impaired ability of the chimeric USP to mediate a stage-specific function associated with the LBD.

Functional characterization of two Ultraspiracle forms (CtUSP-1 and CtUSP-2) from Chironomus tentans

Two forms, CtUSP-1 and CtUSP-2, of the Chironomus tentans homolog of Ultraspiracle (new nomenclature: Chironomus NR2B4) were described and verified as components of the functional ecdysteroid receptor. The two forms differed from each other in the most N-terminal regions of the A/B domain and were tested for several properties. Both forms showed the ability to heterodimerize with CtEcR and interact with a variety of direct repeat and palindromic EcREs, and both conferred specific ligand binding when heterodimerized with EcR. CtUSP-2 showed a twofold higher ponasterone-binding potential than CtUSP-1. Both USP forms demonstrated the ability to activate ecdysteroid-inducible transcription in HeLa cells and the variations in the A/B domain of these forms were not associated with detectable differences in transcriptional activation. Thus, the two forms function similarly. Among species for which USP forms have been reported, Chironomus is the most closely related one evolutionarily to Drosophila. Despite this proximity, a variety of structural differences were noted in both the A/B and E domains of USP between the two species. The Chironomus USP forms lack many of the amino acid residues associated with the ligand-dependent AF2 transactivation function found in all other RXRs and USPs reported so far.

Torsional state of DNA in a transcriptionally hyperactive Balbiani ring of polytene chromosomes

The torsional tension of unconstrained double-helical DNA was determined in transcriptionally hyperactive Balbiani ring 2 (BR2) and in inactive polytene chromosome bands of Chironomus tentans. The method used is based on the dual ability of small intercalating ligands to (a) sense, by differential binding, twists that deviate from that of regular B-form DNA and (b) create positive torsional tension in closed double-stranded DNA, thereby compensating for any negative torsional tension that existed before intercalation. Isolated nuclei of salivary glands were stained with the intercalating fluorescent dye ethidium bromide (EtBr) at various concentrations, and the temporal fluorescence intensity changes (deltaI/I per min) occurring in BR2 and in inactive bands were monitored under a confocal laser scanning microscope during the process of DNA nicking by laser irradiation or DNAase I. From the EtBr concentration at which deltaI/I per min was neither positive nor negative after nicking (i.e. at the equivalence point), the relative twist difference (RTD) was calculated. In bands, it was found to be very small, suggesting that their unconstrained DNA is under low torsional stress. In contrast, the RTD of DNA in highly expanded areas of BR2 was estimated to be negative and of a significant magnitude in absolute terms. This indicates that transcriptionally hyperactive DNA is under considerable negative torsional tension.

High level transactivation by the ecdysone receptor complex at the core recognition motif

Ecdysteroid signaling in insects is mediated by the ecdysone receptor complex that is composed of a heterodimer of the ecdysone receptor and Ultraspiracle. The DNA binding specificity plays a critical role of defining the repertoire of target genes that respond to the hormone. We report here the determination of the preferred core recognition motif by a binding site selection procedure. The consensus sequence consists of a perfect palindrome of the heptameric half-site sequence GAGGTCA that is separated by a single A/T base pair. No binding polarity of the ecdysone receptor/Ultraspiracle heterodimer to the core recognition motif was observed. This core motif mediated the highest level of ligand-induced transactivation when compared to a series of synthetic ecdysone response elements and to the natural element of the Drosophila hsp27 gene. This is the first report of a palindromic sequence identified as the highest affinity DNA binding site for a heterodimeric nuclear hormone receptor complex. We further present evidence that the ligand of the ecdysone receptor preferentially drives Ultraspiracle from a homodimer into a heterodimer. This mechanism might contribute additionally to a tight control of target gene expression.

Immunohistochemical localization of ecdysteroid receptor and ultraspiracle in the epithelial cell line from Chironomus tentans (Insecta, Diptera)

Ecdysteroid receptor (EcR) and its heterodimerization partner, ultraspiracle (USP), were demonstrated in the epithelial cell line from Chironomus tentans by immunohistochemistry. In untreated cells both proteins are present in nuclei as well as in granular compartments of the cytosol. At 1 day after addition of 1-microM 20-OH-ecdysone (20E) total immunofluorescence had increased in the nuclei, whereas the cytoplasmic staining had disappeared. At the 2nd and 3rd days all cells within a vesicle appear identical according to morphological criteria, but the EcR and USP immunoreactivity becomes restricted into patches of neighbouring cells. The hormonally induced changes in the pattern of localization of functional ecdysteroid receptor, the heterodimer of EcR and USP, are discussed in relation to similar effects of 20E on acetylcholinesterase and muscarinic acetylcholine receptor distribution in this cell line.

Antibodies against the D-domain of a Chironomus ecdysone receptor protein react with DNA puff sites in Trichosia pubescens

An antiserum (called AScE/D) against the semiconserved D-domain of a Chironomus tentans ecdysone receptor protein (cEcR) gave indirect immunofluorescence signals at DNA puff sites in Trichosia pubescens. The signals varied in maximum intensity at different DNA puff sites. Control experiments using the secondary rhodamine-labeled anti-rabbit IgG alone, preimmune serum, affinity purified AScE/D (called pABcE/D) and AScE/D preabsorbed with expressing bacterial extract or highly purified bacterially expressed cEcR indicated that the signals obtained at these chromosomal sites were likely to be due to specific interaction between an endogenous sciarid EcR and antibodies against cEcR. This conclusion was supported by observation of signals at certain Ec-inducible primary RNA puff sites. AScE/D signals began to appear at DNA puff sites during L3, the stage when amplification initiates, but at most sites their mean intensity was low and not statistically significant. Sites with AScE/D signals of significant mean intensity at this stage already showed evidence of transcription. The number and strength of transcription signals increased during L4. Comparison of the developmental course of signals for AScE/D, DNA synthesis, RNA presence/synthesis, and puff size for several DNA puffs during late larval- prepupal development showed a closer relationship of AScE/D signals with the initiation of RNA synthesis than with the initiation of DNA synthesis. Therefore, although we cannot absolutely eliminate a direct involvement of EcR in the amplification process at some sites, this investigation gives stronger support for its direct involvement in transcription. Since AScE/D signals are observed at DNA puff sites from the time the latter begin amplification/transcription through their regression, it appears that Ec and EcR are necessary as a sustained stimulus at these regions.

Expression of EcR and USP in Escherichia coli: purification and functional studies

The functional ecdysteroid receptor complex consists of a nuclear receptor heterodimer of ecdysteroid receptor (EcR) and ultraspiracle (USP). EcR and USP of both Chironomus tentans and Drosophila melanogaster were expressed in Escherichia coli as fusion proteins with glutathione S-transferase (GST). Cell lysis and protein solubilization with the anionic detergent sarkosyl yielded preparations of EcR and USP with properties similar to those of the endogenous receptors in various respects. The heterodimer of the expressed proteins specifically bound the labeled ecdysteroid (Ec) [3H]ponasterone A. Furthermore, it preferentially recognized the palindromic ecdysone response element (EcRE) PALI. Interestingly, binding to the PAL1 element was also observed for EcR homodimers. USP homodimers, in turn, preferentially bound to the direct repeat element DR1. When incubated with native polytene chromosomes of Chironomus, EcR/USP specifically accumulated at the early Ec-inducible puff site IV-2B.

The 5' ends of Hantaan virus (Bunyaviridae) RNAs suggest a prime-and-realign mechanism for the initiation of RNA synthesis

We examined the 5' ends of Hantaan virus (HTN) genomes and mRNAs to gain insight into the manner in which these chains were initiated. Like those of all members of the family Bunyaviridae described so far, the HTN mRNAs contained 5' terminal extensions that were heterogeneous in both length and sequence, presumably because HTN also "cap snatches" host mRNAs to initiate the viral mRNAs. Unexpectedly, however, almost all of the mRNAs contained a G residue at position -1, and a large fraction also lacked precisely one of the three UAG repeats at the termini. The genomes, on the other hand, commenced with a U residue at position +1, but only 5' monophosphates were found here, indicating that these chains may not have initiated with UTP at this position. Taken together, these unusual findings suggest a prime-and-realign mechanism of chain initiation in which mRNAs are initiated with a G-terminated host cell primer and genomes with GTP, not at the 3' end of the genome template but internally (opposite the template C at position +3), and after extension by one or a few nucleotides, the nascent chain realigns backwards by virtue of the terminal sequence repeats, before processive elongation takes place. For genome initiation, an endonuclease, perhaps that involved in cap snatching, is postulated to remove the 5' terminal extension of the genome, leaving the 5' pU at position +1.

Immunological studies on the developmental and chromosomal distribution of ecdysteroid receptor protein in Chironomus tentans

Antisera were raised against different domains of a putative ecdysteroid receptor (cEcRH) of Chironomus tentans. All the antisera reacted with a 68,000 dalton protein exhibiting DNA binding properties. Additionally, we were able to demonstrate that the antisera immunoprecipitate protein which binds a radioactively labeled ecdysteroid (Ec), i.e., [3H]ponasterone A, with high specificity. These properties indicate that the antisera recognize specifically an endogenous ecdysteroid receptor protein (cEcR) in C. tentans cells and thus are suitable for the following quantitative and qualitative immunological and immunohistochemical investigations. The cellular level of cEcR varies during development, and it is particularly low in oligopausing larvae. In polytene chromosomes of prepupal salivary glands, cEcR is located at approximately 50 transcriptionally active loci. These loci include both early ecdysteroid (Ec)-inducible puff sites, such as the locus containing the gene coding for the homolog of the E75 protein in Drosophila melanogaster, as well as late Ec-inducible puff-sites. The latter group comprises a locus of a gene specifying the homolog of the D. melanogaster ultraspiracle protein. However, loci of genes coding for salivary gland secretory proteins (e.g., Balbiani ring forming chromosome regions) do not specifically react with the antisera. Thus, the developmental regulation of these genes is not directly controlled by Ec. Polytene chromosomes of oligopausing larvae show hardly any loci that contain cEcR. The few detected correspond, with few exceptions, to the most potent cEcR binding sites found in prepupae.

Cloning of a Chironomus tentans cDNA encoding a protein (cEcRH) homologous to the Drosophila melanogaster ecdysteroid receptor (dEcR)

We have cloned a cDNA sequence coding for a Chironomus tentans steroid hormone receptor homologue which exhibits extensive amino acid sequence co-linearity with the ecdysteroid receptor of Drosophila melanogaster (dEcR; cell 67, 59-77). The DNA-binding domain has 95% and the hormone-binding domain 75% amino acid sequence identity with the cloned dEcR. The gene for this C. tentans protein is located on chromosome II, region 17C, as determined by in situ hybridization to polytene chromosomes of salivary glands. On Northern blots cDNA probes of the cloned gene hybridize to polyadenylated RNA of ca 4.2 kb. The expression of the cloned gene seems to be developmentally regulated and correlates to changes in ecdysteroid titer. Transfection of this C. tentans protein into D. melanogaster Schneider's line 2 cells leads to transcriptional interference with endogenous dEcR on an ecdysteroid-regulated promoter.

Structural and developmental analysis of a gene cloned from the early ecdysterone-inducible puff site, I-18C, in Chironomus tentans

A gene (I-18C) cloned from the early ecdysterone (EDS)-inducible puff site, I-18C, in Chironomus tentans salivary glands, codes by differential processing for at least five transcripts which can be grouped into spliced and unspliced transcripts. The spliced group comprises several RNAs of approx. 4.6 kb, and the unspliced group comprises the 1.8-kb and 6.5-kb RNAs. All these transcripts have a similar or the same transcription start point. The steady-state level of the spliced 4.6-kb RNAs reveals some parallels with EDS concentrations in animals during the various developmental stages analyzed, while the levels of the unspliced 1.8-kb and 6.5-kb RNAs do not correlate with the EDS concentrations.

Identification of a developmentally regulated gene for a 140-kDa secretory protein in salivary glands of Chironomus tentans larvae

Secretory proteins are synthesized in salivary glands of the insect, Chironomus tentans, and assemble in vivo into silk-like threads which aquatic larvae use to construct tubes for filter feeding and pupation. Thus far, all known secretory protein genes contain repetitious protein-coding sequences and are located in cytological structures known as Balbiani rings, giant puffs found on polytene secretory cell chromosomes. In this paper we describe the identification of another secretory protein gene which is comprised of repeated sequences; however, this gene is not located in a Balbiani ring. Two partial cDNA clones from a 3.6-kilobase pair poly(A)+ RNA were sequenced and found to contain two open reading frames for protein synthesis. Antibodies were raised against synthetic oligopeptides whose sequences were derived from these two open reading frames. An immunoaffinity-purified antibody for one of these peptides bound specifically to a 140-kDa secretory protein (sp140). The cDNA sequences contain tandem repeats of 42 base pairs which encode a repeat of 14 amino acids with a composition and oligopeptide sequence similar to other secretory proteins. The C. tentans genome contains about 70 copies of this 42-base pair repeat organized as a contiguous block of 3 kilobase pairs or less. The sp140 gene was mapped by in situ hybridization to polytene chromosome band I-17-B. Developmental studies of protein accumulation, steady-state levels of mRNA, and relative transcription rate suggested that the sp140 gene is developmentally regulated so that maximal expression is achieved during the prepupal stages of the fourth larval instar. Based upon these results we proposed that sp140 gene belongs to a prepupal class of secretory protein genes. While the sp140 gene shares structural and expression characteristics with other secretory protein genes, its unique chromosomal location shows that this multigene family is not restricted to Balbiani rings.

Developmental changes in the responsiveness to ecdysterone of chromosome region I-18C of Chironomus tentans

The presence of nascent RNA in chromosome region I-18C was revealed by the method of induced hybrid formation (IEH) and by use of anti-RNA:DNA antibodies. IEH signals were quantitated, and used as a measure of transcriptional activity in the region. The expansion of the I-18C region was also determined and used as an indication of local chromatin decondensation. Chironomus tentans larvae may undergo oligopause or they may develop subitaneously. It was found that the course of basal activity in I-18C differs substantially in these two modes of development. Most interestingly they also differ in activation of I-18C in response to in vitro ecdysterone treatment. Changes in hormonal responsiveness of I-18C parallel changes in the preexisting state of I-18C decondensation. Oligopause stage 5 animals, being most refractory in this respect, exhibit the most condensed I-18C chromosome region.

Two transcripts of the same ecdysterone-controlled gene are differentially associated with ribosomes

The ecdysterone-controlled gene I-18C of Chironomus tentans produces two transcripts by differential splicing: a 1.8-kb RNA, with an open reading frame (ORF) of 417 nucleotides (nt) and a 4.6-kb RNA, with no ORF longer than 270 nt. Centrifugation of cytoplasmic extracts in velocity sedimentation sucrose gradients and CsCl-buoyant-density gradients demonstrates that the 1.8-kb RNA is incorporated into polysomes. The 4.6-kb RNA, however, exhibits characteristics of free ribonucleic acid-protein complexes and monosomes.

Developmentally regulated expression of a Balbiani ring 1 gene for a 180-kD secretory polypeptide in Chironomus tentans salivary glands before larval/pupal ecdysis

The expression of a Balbiani ring 1 gene that codes for a salivary gland-specific 180-kD secretory polypeptide (sp180) is regulated developmentally. Immunoblots of salivary gland protein incubated with an affinity-purified nonapeptide-reactive antibody demonstrated that the salivary gland content of sp180 increases as much as 10-fold between stages 8 and 10 of the fourth larval instar. Hybridization of RNA dot-blots with an oligonucleotide probe indicated that the observed increase in sp180 was preceded by a parallel 20-fold increase in the steady state level of its mRNA beginning between stages 7 and 8. In vitro nuclear transcription experiments demonstrated that there was a 10-fold acceleration in the rate of sp180 gene transcription between stages 6 and 10. The limited period of expression of the sp180 gene contrasted dramatically with the expression of Balbiani ring genes BR1, BR2 alpha, BR2 beta, and BR6, which code for the sp-I family of fibrous secretory polypeptides. The appearance of sp180 in secretion coincided with microscopically visible changes in the bundling of these fibrous polypeptides. At the same time, we noticed changes in the appearance and consistency of feeding tubes that larvae construct with this secretion. These results lead us to propose that sp180 may modify the structure or utilization of fibrous secretory polypeptides specifically for the assembly of pupation tubes necessary for larval/pupal ecdysis.

Structural transition in inactive Balbiani ring chromatin of Chironomus during micrococcus nuclease digestion

We have analysed by micrococcus nuclease digestion the chromatin structure of genes in the Balbiani ring (BR) regions of a Chironomus cell line. Gel electrophoresis of the DNA fragments reveals a repeating structure which consists of two repeat sizes, a long repeat seen in the large fragments and a small repeat seen in the small fragments. The two repeats hardly overlap, except in a narrow transition zone which is at a different fragment size in the BR 2.2 and the BR 2.1 gene. The sizes of the large repeats fit the repeat of the underlying DNA sequence. The short repeats are between 170 and 180 bp, and after H1 depletion the short repeat in the BR 2.2 gene is 160 bp. Our most favoured interpretation of these data is that in intact chromatin the nucleosomes in the BR genes are phased with respect to the repeating DNA sequence, whereas micrococcus nuclease digestion leads to loss of a nucleosome-positioning constraint and hence to rearrangement of the nucleosomes. Our results imply a possible artefact of nuclease digestion of chromatin, which has to be taken into account in mapping nucleosome positions.

Low degree of ubiquitination of histone 2A in the dipteran Chironomus tentans

A polyclonal antibody to ubiquitin has been prepared and shown to react with both ubiquitin and ubiquitinated histone 2A (uH2A). Applying this antibody in Western blotting experiments, we have observed that the salivary glands of Chironomus tentans contain an unusually low amount of uH2A (1% of histone 2A), while the amount of free ubiquitin is as abundant as in other animal cells, e.g. HeLa cells. The same low content of uH2A was also found in diploid epidermal cells of Chironomus origin suggesting that the low amount is not a characteristic of the polytene state of chromatin in salivary gland cells but rather a property of C. tentans as a species. The significance of the low degree of ubiquitination is discussed in relation to the information available on the organization of Chironomus chromatin into unusually large chromomeric entities.

Two genes in Balbiani ring 2 with metabolically different 75S transcripts

Balbiani ring 2 (BR2) in salivary glands of Chironomus pallidivittatus and C. tentans (two sibling species of the subgenus Camptochironomus) is a favoured model system for studies of gene organization and transcript formation. Here we show that BR2 is more complex than hitherto believed, containing two 75S RNA-producing genes, BR2a and BR2b, present in different 35-40 kb blocks of DNA. The transcripts hybridizing to two different repeat units originating in BR2 differ in size. Further support for the presence of two genes comes from RNA studies during experimentally induced BR2 regression. The amounts of BR2a RNA per cell remain more or less constant throughout the course of the experiment, whereas the BR2b RNA decreases considerably. Under normal conditions there is 5-6 times more BR2a RNA than BR2b RNA. This ratio increases 3-fold under experimental conditions. BR2a and BR2b, although partially homologous, contain repeat units with characteristic differences. BR2a contains a repeat unit that is much more similar to a BR1 repeat than it is to the BR2b repeat. The possibility is discussed that a Balbiani ring in general represents an integrated set of active genes rather than a singe gene.

Bacterial meningitis in Johannesburg--1980-1982

A 2-year retrospective study of aetiology, age distribution, seasonal variation and antimicrobial sensitivity patterns of bacteria isolated from patients with meningitis in five Johannesburg hospitals for White, Black, Coloured and Asian patients was performed. Neisseria meningitidis was isolated most frequently, followed by Streptococcus pneumoniae, Haemophilus influenzae, Escherichia coli and Streptococcus group B. In the Black population 73% of the meningococcal infections occurred in patients over 3 years of age, and the majority of these infections were caused by serogroup A organisms. Virtually all (93%) of the H. influenzae infections occurred in children of less than 3 years of age. Of the isolates tested, 16% of the meningococci, 4,5% of the H. influenzae and 47% of the pneumococci were resistant to sulphadiazine, ampicillin and penicillin respectively.

Chromatin structure of a hyperactive secretory protein gene (in Balbiani ring 2) of Chironomus

We examined the chromatin structure of a Balbiani ring (secretory protein gene) in the salivary glands of Chironomus larvae in its hyperactive state after stimulation with pilocarpine. For the inactive state of the gene an established tissue culture cell line, not expressing the gene, was used. Electron microscopy showed an RNA polymerase density of approximately 38/microns. Micrococcal nuclease digestion of purified nuclei followed by DNA transfer and hybridization revealed a smear with no recognizable discrete DNA fragments. Without pilocarpine stimulation a faint nucleosomal repeat was superimposed upon the smear, and in tissue culture cells a clear nucleosomal repeat was revealed. The restriction enzyme XbaI, which has a 6-bp recognition sequence, cut the gene in the hyperactive chromatin state, but not in its inactive conformation. The combined results are best explained by the absence of most of the nucleosomes in this hyperactive RNA polymerase II transcribed gene.

The activity of Balbiani rings 1 and 2 in salivary glands of Chironomus tentans larvae under different modes of development and after pilocarpine treatment

The activity of the Balbiani rings 1 and 2 (BR1 and BR2) in the salivary gland was followed during development of fourth instar larvae of Chironomus tentans under different modes of development, with or without a previous pilocarpine treatment. The activity was determined in parallel by two different methods, by incorporation of [3H]uridine into BR-RNA (75 S) and by morphometry of BR1 and of BR2. In glands of untreated larvae BR2 does not change dramatically except for a depression of activity during oligopause (resting phase). BR1 is completely inactive during this phase but exhibits a pronounced activity maximum in the middle of the prepupal period, in subitaneously developing (i.e., uninterrupted) as well as in postoligopause cultures. After pilocarpine treatment the activity of BR2 (rather than of BR1) is generally increased. The extent of this stimulation, however, is strongly development dependent. A most striking activity difference is observed in postoligopause between animals of stage 5 and of stage 6. The relationship between BR2 activity and degree of emptying of the salivary gland lumen was investigated. A model is proposed in which BR2 activity is conceived as being regulated by two parameters: by the degree of filling of the gland lumen and by the stage and mode of development of the larva.

Ultrastructural studies of Chironomus salivary gland cells in different states of Balbiani ring activity

Chironomus tentans fourth instar larvae were awakened from oligopause (diapause) and treated with pilocarpine to stimulate Balbiani ring transcriptional activity. Salivary glands were fixed, sectioned and examined by conventional and stereo-electron microscopy. Balbiani ring RNP lateral fiber densities were measured in well-formed regions with clear Balbiani ring granules arranged along chromatin transcription axes. Despite an up to ten-fold range in Balbiani ring transcriptional activity [10, 12, 14], we observed no significant difference in lateral fiber densities. These data are discussed in terms of the variety of mechanisms for modulating overall transcriptional activity, including recruitment of parallel transcription units in the polytene chromosome. The lack of other major ultrastructural changes at the nuclear envelope and within the domains of tubular rough endoplasmic reticulum argue strongly against a major dismantling of subcellular structure during the induced oligopause.

Isolation of DNA from single microsurgically excised bands of polytene chromosomes of Chironomus

A method is described for excising by a glass knife single bands of isolated polytene chromosomes of the salivary glands of Chironomus tentans larvae. DNA strands were isolated from cut-out bands and their contour lengths were determined on electron micrographs. The mean contour length of DNA strands isolated from the double band I-8A was about twice that of the single band I-11B, namely 63 versus 34 micrometers. The described method may be applicable for molecular studies on single bands (e.g., by DNA cloning).

Heat shock phenomena in Chironomus tentans I. In vivo effects of heat, overheat, and quenching on salivary chromosome puffing

Incubation of 4th instar larvae of Chironomus tentans at elevated temperatures leads in salivary and Malpighian chromosomes to the appearance of 4-5 new puffs. Previously present puffs, particularly Balbiani rings in salivary chromosomes, become drastically reduced. The reactions of region IV-5C and Balbiani ring 1 and 2 in salivary glands are quantitatively analyzed. Statistically significant heat shock effects are observed already after 5 min and reach a maximum between 30 and 60 min. The effective temperature range is small (between 33 to 40 degrees C) with an optimum at 37 degrees C. Above 40 degrees C, i.e., at overheat shock temperatures, heat shock reactions are suppressed. Larvae heat or overheat shocked for 1-7 h or 15-30 min, respectively, survive when returned to normal culturing temperatures. The recovery from heat shock of the puffing pattern occurs in two phases: a fast one (10-20 min) and a slow one (up to 5 h) sometimes separated by a period of backlash. Quenching of overheat shocked larvae does not result in a delayed heat shock reaction.

Elemental analysis of solid microscopic samples in the flameless atomic absorption cuvette

Solid microscopic samples are precisely located by means of a newly developed applicator under microscopic control in the center of a flameless graphite tube cuvette. The parts of the applicator that reach into the cuvette are made of quartz which can be cleaned by heating. The values for the K and Na content of samples such applied are highly reproducible. No contamination could be detected. Solid samples yield higher signals than liquid samples. A method of calibration is described which uses lyophilized pieces of egg albumin containing known amounts of K and Na as standards.

A gravimetric system for lyophilized samples in the sub-microgram range

A new quartz fiber balance is described which is evacuated and electrically shielded. This balance minimizes the problems of moisture uptake by the lyophilized sample, air convection inside the balance and static electricity. Besides it offers a wider useful weighing range and a higher handling comfort. It could be shown that in the regular (i.e. not evacuated) balance the moisture uptake varies considerably with the humidity of the air and with the kind of sample analyzed, and that it might be greater than previously reported.

Change in nuclear potassium electrochemical activity and puffing of potassium-sensitive salivary chromosome regions during Chironomus development

Changes in nuclear K+ electrochemical activity and total nuclear K+ content in salivary glands of Chironomus tentans were measured with ion-selective microelectrodes based on valinomycin and with flameless atomic absorption spectrometry, respectively. The K+ activity increased by a factor of 2.6 and the total K+, by a factor of 1.5 as oligopausing larvae developed into prepupae. The extent of decondensation (puffing) of K+-sensitive regions in the polytene chromosomes underwent a parallel increase during this developmental event. In vitro culture of glands from oligopausing larvae resulted in similar changes with respect to nuclear K+ activity and puffing.

Mass isolation ofpolytene nuclei from Chironomus salivary glands

In this paper we describe a method for the rapid mass isolation of polytene nuclei from Chironomus salivary glands. The procedure for the isolation of glands involves 5 principal steps; (a) freezing Chironomus larvae in liquid propane; (b) breaking open frozen animals in a pre-cooled mortar; (c) thawing the fragments in sucrose medium, free of divalent cations; (d) pressing the suspension of broken animals through a system of regularly spaced capillary constrictions of free organs; and (e) enrichment of glands by differential sedimentation and removal of contaminating material under a dissecting microscope. The nuclear isolation procedure is a large scale modification of a method previously described by Robert, using digitonin as a non-ionic detergent to solubilize cytoplasma and secretion without affecting the nuclear membrane. Nuclei obtained by this method show structural integrity and an unchanged chromosomal banding pattern. Their incorporation of UTP is within the same range as reported by other authors for nuclei by hand dissection.

Correlated changes of Balbiani ring expansion and secretory protein synthesis in larval salivary glands of Chironomus tentans

Salivary glands of various stages of the last larval instar of Chironomus tentans were quantitatively analyzed with respect to the expansion of their Balbiani rings (B1, B2, B3) by a fast green staining procedure as well as to the rate of synthesis of their secretory proteins (S1, S2, S3) by a scintillation counting procedure of electrophoretic fractions. The extent of expansion of B1, B2 and B3 correlates positively with the rate of synthesis of S3, S2 and S1, respectively. With B1 and S3 these parameters undergo a parallel and developmentally specific change being rather depressed in intermolt, and particularly in diapausing animals.

Differential Effects of K+ and Na+ on Specific Bands of Isolated Polytene Chromosomes of Chironomus Tentans

Previous investigations on the effects of monovalent cations on the gene activities (formation of puffs) of polytene chromosomes utilized whole salivary glands or nuclei and suggested that the K+/Na+ ratio in the nuclear sap was of primary importance in influencing gene activities. To determine whether these effects of ions were direct or indirect, we have employed isolated polytene chromosomes incubated in salt solutions of varying ionic composition. Our observations reveal differential effects of K+, Na+, Mg2+, Ca2+ and combinations thereof on specific chromosome regions. The band at region I-18-C that is specifically affected by K+ is the same one that puffs when salivary gland nuclei are incubated in a K+-rich medium and this is believed to be an ecdysone-specific puff. Bands at region I-19-A are specifically affected by Na+ and are the same ones that form puffs when salivary gland nuclei are incubated in a Na+-rich medium. This region is believed to be juvenile hormone-specific. Effects on the chromosome are also described that are the result of incubation in solutions containing Mg2+ and Ca2+. Analogies are drawn between the observed effects of ions on isolated chromosomes and their effects on chromatin isolated from mammalian cells. For example, when chromatin is exposed to solutions of increasing ionic strength, hydration is followed by aggregation and histone dissociation. This may be analogous to what is observed in the isolated chromosome under similar conditions; namely, expansion, contraction and expansion.