Structure of the yolk syncytial layer in the larvae of whitefishes: A histological study

The yolk syncytial layer (YSL) is a symplastic provisory system that forms at the early stages of embryogenesis of teleosts. The YSL serves morphogenetic, trophic, and immune functions. Despite its important role in development, data on the structure of YSL is scarce. In the present study, comparative histological research on the features of YSL structure in the development of larvae of four economically important species of Coregonidae (Salmoniformes)—Coregonus peled, Coregonus muksun, Coregonus nasus, and Stenodus leucichthys nelma—is presented. The YSL of the larvae of Coregonidae has a complex, differentiated structure. Functional regionalization of YSL cytoplasm, possibly determined by the specific features of nutrient assimilation, is typical for all aforementioned species. Cytoplasm that encircles a large oil globule appears striated. A division into an inner area, filled with yolk inclusions, and an outer, smoother homogeneous area, can be noted in the cytoplasm surrounding the yolk mass. The oil globule is retained after complete utilization of the yolk mass. The inequality of thickness of YSL along anteroposterior and dorsoventral axes also indicates the functional regionalization. The dorsomedial area of YSL, located under the intestine, is the least thick. Dorsolateral areas are strongly incrassated and envelop the intestine from two sides. Gigantic nuclei of exceptionally complex form are typical for YSL. Specific features apply to the form of YSL and its nuclei. Based on the obtained results, a fundamental similarity in organization of the YSL of larvae of the studied whitefishes can be concluded; however, its specific variations distinguishable on a histological level can be discussed.     

Diversity and succession of pelagic microorganism communities in a newly restored Illinois River floodplain lake

Stenotopic specialization to a fragmented habitat promotes the evolution of genetic structure. It is not yet clear whether small-scale population structure generally translates into large-scale intraspecific divergence. In the present survey of mitochondrial genetic structure in the Lake Tanganyika endemic Altolamprologus (Teleostei, Cichlidae), a rock-dwelling cichlid genus comprising A. compressiceps and A. calvus, habitat-induced population fragmentation contrasts with weak phylogeographic structure and recent divergence among genetic clades. Low rates of dispersal, perhaps along gastropod shell beds that connect patches of rocky habitat, and periodic secondary contact during lake level fluctuations are apparently sufficient to maintain genetic connectivity within each of the two Altolamprologus species. The picture of genetic cohesion was interrupted by a single highly divergent haplotype clade in A. compressiceps restricted to the northern part of the lake. Comparisons between mitochondrial and nuclear phylogenetic reconstructions suggested that the divergent mitochondrial clade originated from ancient interspecific introgression. Finally, ‘isolation-with-migration’ models indicated that divergence between the two Altolamprologus species was recent (67–142 KYA) and proceeded with little if any gene flow. As in other rock-dwelling cichlids, recent population expansions were inferred in both Altolamprologus species, which may be connected with drastic lake level fluctuations.     

Four new species of <Emphasis Type="Italic">Paradiscogaster</Emphasis> Yamaguti, 1934 (Digenea: Faustulidae) from batfishes (Perciformes: Ephippidae) on the Great Barrier Reef,Australia

Examination of three species of batfishes (Teleostei: Epphippidae) from off Lizard and Heron Islands on the Great Barrier Reef led to the discovery of specimens of the trematode genus Paradiscogaster Yamaguti, 1934 (Digenea: Faustulidae). Morphological analysis demonstrated that the new specimens represented four morphotypes which we interpret to be new species: Paradiscogaster martini n. sp., P. vichovae n. sp. and P. brayi n. sp. from Platax orbicularis (Forsskål) and P. pinnatus (Linnaeus) off Lizard Island, and P. nitschkei n. sp. from P. teira (Forsskål) off Heron Island. Published material was re-examined and the specimens identified as P. chaetodontis okinawensis Yamaguti, 1971 from P. pinnatus from Okinawa, Japan, actually represent the new species P. brayi n. sp., demonstrating that some species of Paradiscogaster have wide geographical distributions. ITS2 rDNA data for the four morphotypes differ by 4–39 base pairs confirming the delineation of the four species proposed. A feature of this study is the recognition of Platax spp. as an important host group for Paradiscogaster, with the new species placing them as the second richest host group for these parasites after the Chaetodontidae.     

Phylogenetic and Expression Analysis of Pear Yellow Stripe-Like Transporters and Functional Verification of <Emphasis Type="Italic">PbrYSL4</Emphasis> in Pear Pollen

Yellow stripe-like (YSL) family transporters, belonging to the oligopeptide transporter family, are significant iron transport proteins. In this study, we provided a genome-wide identification and analysis of the YSL gene family in Pyrus bretschneideri. We found eight YSL gene members in pear, clustered into four main groups in the phylogenetic tree. Segmental duplication has played a key role in the expansion of the pear YSL family. The pollen activity analysis indicated that the low concentration of iron ion was beneficial to both pear pollen germination and pollen tube growth. Among the eight YSL genes, PbrYSL4 had particularly high expression in all pear tissues; it was significantly responsive to change in the external iron ion supply in the pollen cultivation in vitro. Moreover, expression of PbrYSL4 in yeast mutant Δccc1 (Ca ²⁺ -sensitive cross-complementer 1 mutant) made Δccc1 restore growth in high iron medium. These data together suggest that PbrYSL4 was involved in the movement of iron in the pear pollen tube growth.     

Food resource partitioning of the <Emphasis Type="Italic">Mustelus lunulatus</Emphasis> and <Emphasis Type="Italic">Mustelus henlei</Emphasis> (Elasmobranchii: Carcharhiniformes)

The feeding habits and trophic ecology of Mustelus lunulatus and Mustelus henlei in the central coast of the Colombian Pacific were evaluated and compared to determine whether there was trophic niche overlap or resource partitioning between these two sympatric shark species. A total of 59 prey items were identified and grouped into 10 taxonomic categories. Mustelus lunulatus fed in large proportion on Stomatopoda and Brachyura, whereas M. henlei fed almost exclusively on Teleostei. Dendrobranchiata, Cephalopoda, Anomura and Polychaeta complemented the diets of both species. There were significant differences in diet between the two species, and there was an ontogenetic diet shift in Mustelus lunulatus, with Stomatopoda being the main prey item of juveniles and Brachyura the main prey item of adults. Dietary overlap (by sex and size) was low between species, but it was high for each species, with significant overlap between juveniles and adults of M. lunulatus and M. henlei, and between males and females of M. henlei. There were differences in the trophic levels of the species, sexes and sizes. This study suggests there is food resource partitioning, and differing ecological function of the two Mustelus species in the food web of the study area.     

<Emphasis Type="Italic">Coregonus peled</Emphasis> (Gmelin) transplanted into Ulaagchny Khar lake (western mongolia) showed no evidence of hybridization with other introduced <Emphasis Type="Italic">Coregonus</Emphasis> species

Coregonus peled (Gmelin) (Teleostei: Salmoniformes: Coregonidae), which is considered an important object of coldwater aquaculture, had been successfully introduced into an enclosed Western Mongolian lake Ulaagchny Khar in the early 1980s. At the same time larvae of two other Coregonus species—Baikal omul C. migratorius (Georgi) and least cisco C. sardinella Valenciennes—had also been released into the lake. Baikal omul was then reported as a naturalized species. This might have caused interspecific hybridization and gene introgression. Identification of coregonids by morphology can be problematic, so to determine which species was dominant in the lake (we presumed it was peled) and if its gene pool was affected by other introduced Coregonus species we sampled 40 individuals and analyzed them by sequencing a fragment of mtDNA cyt b and by allozyme electrophoresis. The analysis showed that all the fish belonged to C. peled with no evidence of admixture from other coregonid species. Taking into account mass release of both species in 1980s, it is evident that naturalization of peled in the lake was much more successful than that of Baikal omul.     

Molecular evolution of mobile elements of the <Emphasis Type="Italic">gypsy</Emphasis> group: A homolog of the <Emphasis Type="Italic">gag</Emphasis> gene in <Emphasis Type="Italic">Drosophila</Emphasis>

Retrotransposons of the gypsy group of Drosophila melanogaster that are structurally similar to retroviruses of vertebrates occupy an important place among retroelements of eukaryotes. The infectious abilities of some retrotransposons of this group (gypsy, ZAM, and Idefix) have been demonstrated experimentally, and therefore they are true retroviruses. It is supposed that retrotransposons can evolve acquiring new components, the sources of which remain to be elucidated. In this work, the CG4680gene (Gag related protein, Grp) homologous to gag of retrotransposons of the gypsy group has been identified in the genome of D. melanogaster and characterized. The Grp gene product has a highly conserved structure in different species of the Drosophilidae family and is under of purifying selection, which suggests its important genomic function in Drosophila. In view of the earlier data, it can be concluded that homologous genes of all components of gypsy retrotransposons are present in the Drosophila genome. These genes can be both precursors and products of domestication of retrovirus genes.     

Genetic structure of the populations of <Emphasis Type="Italic">Dactylorhiza ochroleuca</Emphasis> and <Emphasis Type="Italic">D. incarnata</Emphasis> (Orchidaceae) in the area of their joint growth in Russia and Belarus

We carried out an allozyme analysis to investigate polymorphism and genetic structure of the populations of D. incarnata and D. ochroleuca in regions of their joint growth in Russia and Belarus. We found that D. ochroleuca individuals in the populations of the Urals and Siberia, which are distant fragments from the main range of the species, do not differ significantly from individuals within the main part of the area (Belarus) on the basis of the allelic composition of eight gene loci. We revealed that D. ochroleuca and D. incarnata are differentiated by different alleles of the GDH locus. Thus, we established a genetic marker suitable to distinguish these closely related taxa. In addition to the GDH locus, D. ochroleuca and D. incarnata in the places of their joint growth, differ in the allelic structure of the PGI and NADHD loci. D. incarnata from the Urals and Siberia were polymorphic for both loci, and individuals from Belarus were polymorphic for one locus (PGI). In contrast, all D. ochroleuca individuals growing in sympatric populations with polymorphic D. incarnata were homozygous for the same alleles. Thus, comparison of the genetic structure of D. ochroleuca and D. incarnata points to the existence of a genetic isolation and a functioning isolation mechanism even under conditions of their joint growth. We found that the GDH locus in D. incarnata is polymorphic only in populations which grow together with D. ochroleuca, with exception a few examples. Thus, we conclude that variability of the GDH locus in D. incarnata is associated with hybridization with D. ochroleuca.     

On the multicomponent nature of <Emphasis Type="Italic">Halobacterium salinarum</Emphasis> flagella

Filaments of the flagellum of the halophilic archaeon Halobacterium salinarum consist of five flagellins: A1, A2, B1, B2, and B3, which are encoded by five genes localized in tandem in two flgA and flgB operons. While the role of flagellins A1 and A2 has been determined, the role of the proteins, B operon products, is still unclear. A mutant strain of H. salinarum with deleted A and B flagellin genes (ΔflgAΔflgB) has been obtained for the first time. This strain has been used to create and analyze the strains carrying only individual B1 or B3 flagellin genes. Cells of the ΔflgAΔflgB strain were shown to have short filamentous formations, 7–8 nm thick, which we have named as X-filaments. It has been shown that X-filaments consist of a protein immunologically related to flagellins A and B. Expression of the B1 and B3 genes is suppressed in the absence of A1, A2, and B2. It has been shown that flagellins B1 and B3 cannot be substituted for flagellin B2 upon the formation of a curved hook-like structure, which serves as a connecting element between the flagellar filament and the motor axis. The multicomponent nature of flagella is discussed in the light of their possible involvement in other cell processes besides providing motility.     

Integrated gene mapping and synteny studies give insights into the evolution of a sex proto-chromosome in <Emphasis Type="Italic">Solea senegalensis</Emphasis>

The evolution of genes related to sex and reproduction in fish shows high plasticity and, to date, the sex determination system has only been identified in a few species. Solea senegalensis has 42 chromosomes and an XX/XY chromosome system for sex determination, while related species show the ZZ/ZW system. Next-generation sequencing (NGS), multi-color fluorescence in situ hybridization (mFISH) techniques, and bioinformatics analysis have been carried out, with the objective of revealing new information about sex determination and reproduction in S. senegalensis. To that end, several bacterial artificial chromosome (BAC) clones that contain candidate genes involved in such processes (dmrt1, dmrt2, dmrt3, dmrt4, sox3, sox6, sox8, sox9, lh, cyp19a1a, amh, vasa, aqp3, and nanos3) were analyzed and compared with the same region in other related species. Synteny studies showed that the co-localization of dmrt1-dmrt2-drmt3 in the largest metacentric chromosome of S. senegalensis is coincident with that found in the Z chromosome of Cynoglossus semilaevis, which would potentially make this a sex proto-chromosome. Phylogenetic studies show the close proximity of S. senegalensis to Oryzias latipes, a species with an XX/XY system and a sex master gene. Comparative mapping provides evidence of the preferential association of these candidate genes in particular chromosome pairs. By using the NGS and mFISH techniques, it has been possible to obtain an integrated genetic map, which shows that 15 out of 21 chromosome pairs of S. senegalensis have at least one BAC clone. This result is important for distinguishing those chromosome pairs of S. senegalensis that are similar in shape and size. The mFISH analysis shows the following co-localizations in the same chromosomes: dmrt1-dmrt2-dmrt3, dmrt4-sox9-thrb, aqp3-sox8, cyp19a1a-fshb, igsf9b-sox3, and lysg-sox6.     

Composition and abundance of microbiota in the pharynx in patients with laryngeal carcinoma and vocal cord polyps

The pharynx is an important site of microbiota colonization, but the bacterial populations at this site have been relatively unexplored by culture-independent approaches. The aim of this study was to characterize the microbiota structure of the pharynx. Pyrosequencing of 16S rRNA gene libraries was used to characterize the pharyngeal microbiota using swab samples from 68 subjects with laryngeal cancer and 28 subjects with vocal cord polyps. Overall, the major phylum was Firmicutes, with Streptococcus as the predominant genus in the pharyngeal communities. Nine core operational taxonomic units detected from Streptococcus, Fusobacterium, Prevotella, Granulicatella, and Veillonella accounted for 21.3% of the total sequences detected. However, there was no difference in bacterial communities in the pharynx from patients with laryngeal cancer and vocal cord polyps. The relative abundance of Firmicutes was inversely correlated with Fusobacteria, Proteobacteria, Actinobacteria, and Bacteroidetes. The correlation was evident at the genus level, and the relative abundance of Streptococcus was inversely associated with Fusobacterium, Leptotrichia, Neisseria, Actinomyces, and Prevotella. This study presented a profile for the overall structure of the microbiota in pharyngeal swab samples. Inverse correlations were found between Streptococcus and other bacterial communities, suggesting that potential antagonism may exist among pharyngeal microbiota.     

Precise transfers of genes for high grain iron and zinc from wheat-<Emphasis Type="Italic">Aegilops</Emphasis> substitution lines into wheat through pollen irradiation

Nearly 2 billion people worldwide are suffering from iron (Fe) deficiency anemia and zinc (Zn) deficiency. The available elite bread wheat cultivars have inherently low grain micronutrient content. Biofortification for grain Fe and Zn content is one of the most feasible and cost-effective approach for combating widespread deficiency of the micronutrients. QTL controlling high grain Fe and Zn have been mapped on groups 2 and 7 chromosomes of Triticeae. The present study was initiated for precise transfers of genes for high grain Fe and Zn on group 2 and 7 chromosomes of wheat-Aegilops substitution lines to wheat cultivars using pollen radiation hybridization. The pollen radiation hybrids (PRH₁) derived from 1.75 krad irradiated spikes showed the presence of univalents and multivalents in meiotic metaphase-I indicating the effectiveness of radiation dose. In the advanced generation PRH₅, the plants selected with stable chromosome number and high grain Fe and Zn content were analyzed with wheat groups 2 and 7 chromosome specific intron targeted amplified polymorphism (ITAP) markers of the metal homeostasis genes to monitor the transfers of alien genes from the substituted Aegilops chromosomes. The group 2 chromosome derivatives showed the presence of NAS2, FRO2, VIT1, and ZIP2 Aegilops genes whereas the group 7 derivatives had YSL15, NAM, NRAMP5, IRO3, and IRT2 Aegilops genes. The pollen radiation hybrids of both the groups 2 and 7 chromosomes showed more than 30% increase in grain Fe and Zn content with improved yield than the elite wheat cultivar PBW343 LrP indicating small and compensating transfers of metal homeostasis genes of Aegilops into wheat.     

The iron-chelate transporter OsYSL9 plays a role in iron distribution in developing rice grains

Key message

Rice OsYSL9 is a novel transporter for Fe(II)-nicotianamine and Fe(III)-deoxymugineic acid that is responsible for internal iron transport, especially from endosperm to embryo in developing seeds.

Abstract

Metal chelators are essential for safe and efficient metal translocation in plants. Graminaceous plants utilize specific ferric iron chelators, mugineic acid family phytosiderophores, to take up sparingly soluble iron from the soil. Yellow Stripe 1-Like (YSL) family transporters are responsible for transport of metal-phytosiderophores and structurally similar metal-nicotianamine complexes. Among the rice YSL family members (OsYSL) whose functions have not yet been clarified, OsYSL9 belongs to an uncharacterized subgroup containing highly conserved homologs in graminaceous species. In the present report, we showed that OsYSL9 localizes mainly to the plasma membrane and transports both iron(II)-nicotianamine and iron(III)-deoxymugineic acid into the cell. Expression of OsYSL9 was induced in the roots but repressed in the nonjuvenile leaves in response to iron deficiency. In iron-deficient roots, OsYSL9 was induced in the vascular cylinder but not in epidermal cells. Although OsYSL9-knockdown plants did not show a growth defect under iron-sufficient conditions, these plants were more sensitive to iron deficiency in the nonjuvenile stage compared with non-transgenic plants. At the grain-filling stage, OsYSL9 expression was strongly and transiently induced in the scutellum of the embryo and in endosperm cells surrounding the embryo. The iron concentration was decreased in embryos of OsYSL9-knockdown plants but was increased in residual parts of brown seeds. These results suggested that OsYSL9 is involved in iron translocation within plant parts and particularly iron translocation from endosperm to embryo in developing seeds.

     

New species of Telenominae (Hymenoptera,Scelionidae) from the palaearctic fauna

Four new species of Telenominae of the genera Telenomus and Platytelenomus, collected in the territory of the Ukraine, Hungary, and Japan, were described: Telenomus (T.) bicolorus Kononova, T. (T.) ardens Kononova, (T.) michaylovi Kononova, and Platytelenomus mirabilis Kononova. Brief morphological characteristics of the genera Telenomus and Platytelenomus are given, and some notes concerning biology and geographical distribution of the species are presented. Telenomus (T.) bicolorus differs from all the known species of the genus Telenomus in the two-colored body: head and thorax yellow with brownish tint ventrally, mesothorax and abdomen black. The main distinguishing feature of T. (T.) ardens is its smooth shining body, T. (T.) michaylovi is similar to T. (T.) rudis Kozlov. These species can be distinguished by the structure of their antenna. The second to fourth segments of the antennal clava are transverse in T. (T.) michaylovi and are as long as wide in T. (T.) rudis. In addition, the abdominal stem and abdominal tergite II are smooth and shining, while the abdominal stem in T. (T.) rudis is striate along the entire length, and tergite II is finely striate along half of its length. Platytelenomus mirabilis is closely related to P. danubialis Szelényi, but differs in the strongly flattened body, sculpture of the abdominal stem and tergite II, and coloration of the legs. The thorax of P. mirabilis is 4–5 times as wide as high, the abdominal stem is striate along the entire length, tergite II is striate at the base, and the legs, including coxae, are yellow. The thorax of P. danubialis is 4 times as wide as high, the abdominal stem and tergite II are smooth and shining, and the legs are brown.     

Detection of <Emphasis Type="Italic">Helicobacter</Emphasis> DNA in different water sources and penguin feces from Greenwich,Dee and Barrientos Islands,Antarctica

Helicobacter spp. colonize the gastrointestinal tract of humans and animals and have been associated with gastrointestinal diseases. Antarctic habitats are considered pristine ecosystems, but the increase in human activity could be introducing human bacteria hosted into waters and wildlife. However, Helicobacter spp. occurrence has not been studied in Antarctica. The aim of our study was to detect the Helicobacter DNA in different water sources and penguin feces from Greenwich, Dee and Barrientos Islands during summer of 2012 and 2013. High Helicobacter proportion was observed in water sources amplifying the 16S rRNA (33/40) and 23S rRNA genes (37/40) by semi-nested PCR. Similar results were observed in feces from Gentoo penguins (16S rRNA: 32/39, and 23S rRNA: 28/39) and Chinstrap penguins (16S rRNA: 16/17, and 23S rRNA: 15/17) by PCR. The phylogenetic relationship of 16S rRNA and 23S rRNA sequences from penguin feces was closely related to Helicobacter brantae. Analyses of 16S rRNA sequences showed that the majority of water samples are related to penguin (3/6) and Helicobacter pylori (2/6) sequences, but the 23S rRNA sequences matched with Campylobacter and Arcobacter. These results show for the first time the presence of the genus Helicobacter in different Antarctica water sources and in Gentoo and Chinstrap penguin feces. A few 16S rRNA sequences are very closely related to H. pylori, but specific glmM and ureA H. pylori genes were not detected. More studies are needed to determine the Helicobacter species present in this ecosystem and to establish the human impact in these Antarctic Islands.     

The structure of the claspettes in the male genitalia of the subgenus <Emphasis Type="Italic">Ochlerotatus</Emphasis> Lynch Arribalzaga of the genus <Emphasis Type="Italic">Aedes</Emphasis> Meigen (Diptera,Culicidae) and their diagnostic significance

The structure of the claspettes (modified projections in the male genitalia) in species of the subgenus Ochlerotatus Lynch Arribalzaga of the genus Aedes Meigen is described in detail. A thorough investigation of the three-dimensional structure of the claspettes is necessary for identification of the Ochlerotatus species from Russia. The study of 30 species of Ochlerotatus demonstrated that frequently the use of the claspette structure as a diagnostic character was incorrect when the claspettes were described as flat structures. Examination of the three-dimensional structure of the claspettes has revealed characters differentiating Aedes diantaeus, A. intrudens and A. pullatus; A. communis, A. punctor, and A. hexodontus; A. annulipes, A. excrucians, and A. euedes, as well as some other species.     

Overexpression of a <Emphasis Type="Italic">Miscanthus sacchariflorus</Emphasis> yellow stripe-like transporter <Emphasis Type="Italic">MsYSL1</Emphasis> enhances resistance of <Emphasis Type="Italic">Arabidopsis</Emphasis> to cadmium by mediating metal ion reallocation

The yellow stripe-like (YSL) family of transporters mediates the uptake, translocation, and distribution of various mineral elements in vivo by transferring metal ions chelated with phytosiderophore or nicotianamine (NA). However, little is known about the roles of the YSL genes against cadmium in planta. In this study, we first cloned and characterized a vital member of the YSL gene family, MsYSL1, from the bioenergy plant Miscanthus sacchariflorus. MsYSL1 localized in the plasma membrane and was widely expressed throughout the whole seedling with the highest expression level in the stem. In addition, its expression in the root was stimulated by excess manganese (Mn), cadmium (Cd), and lead, and a shortage of iron (Fe), zinc (Zn), and copper. Functional complementation in yeast indicated that MsYSL1 showed transport activity for Fe(II)–NA and Zn–NA, but not for Cd–NA. Although they exhibited no significant differences versus the wild type under normal cultivation conditions, MsYSL1-overexpressing Arabidopsis lines displayed a higher resistance to Cd accompanied by longer root lengths, lower Cd, Zn, and Mn levels in roots, and higher Cd, Fe, and Mn translocation ratios under Cd stress. Moreover, genes related to NA synthesis, metal translocation, long-distance transport, and Cd exclusion were highly induced in transgenic lines under Cd stress. Thus, MsYSL1 may be an essential transporter for diverse metal–NAs to participate in the Cd detoxification by mediating the reallocation of other metal ions.