Silencing of six susceptibility genes results in potato late blight resistance

Phytophthora infestans, the causal agent of late blight, is a major threat to commercial potato production worldwide. Significant costs are required for crop protection to secure yield. Many dominant genes for resistance (R-genes) to potato late blight have been identified, and some of these R-genes have been applied in potato breeding. However, the P. infestans population rapidly accumulates new virulent strains that render R-genes ineffective. Here we introduce a new class of resistance which is based on the loss-of-function of a susceptibility gene (S-gene) encoding a product exploited by pathogens during infection and colonization. Impaired S-genes primarily result in recessive resistance traits in contrast to recognition-based resistance that is governed by dominant R-genes. In Arabidopsis thaliana, many S-genes have been detected in screens of mutant populations. In the present study, we selected 11 A. thaliana S-genes and silenced orthologous genes in the potato cultivar Desiree, which is highly susceptible to late blight. The silencing of five genes resulted in complete resistance to the P. infestans isolate Pic99189, and the silencing of a sixth S-gene resulted in reduced susceptibility. The application of S-genes to potato breeding for resistance to late blight is further discussed.     

Effect of retinoids on <Emphasis Type="Italic">Post2 Нох</Emphasis> gene expression in nereid polychaetes

Retinoic acid (RA) plays an important role in vertebrate development and regeneration. RA signalling directly regulates the expression of Hox genes, being in this way involved in the patterning of the anterior-posterior (AP) axis of vertebrate embryos. So far the relationship between retinoic acid signalling and Hox genes has been shown only for chordates. In this study we incubated juvenile worms and regenerating worms of two polychaete species from the family Nereididae, Alitta virens and Platynereis dumerilii, with all-trans-retinal, the precursor of retinoic acid. Under the influence of all-trans-retinal the anterior expression boundary of Post2 Нох gene shifted towards the anterior end both in intact and in regenerating worms of both species. Our data indicate the existence of a relationship between RA signalling and Нох genes in Protostomia.     

Structural and functional organization of the plasmid regulons of <Emphasis Type="Italic">Rhizobium leguminosarum</Emphasis> symbiotic genes

The structure of the plasmid locus containing the sym-genes (nod-, nif-, and fix-operons) was investigated in eight Rhizobium leguminosarum strains differing in their origin and host specificity, including five strains of the viciae biovar—symbionts of pea (3), forage beans (1), and Vavilovia (1)—as well as three strains of the biovar trifolii (clover symbionts). Strains of R. leguminosarum bv. viciae, which possess the nodX gene (controlling acetylation of the Nod factor, which is responsible for the ability of rhizobia to form symbioses with a broad spectrum of hosts, including the “Afghan” pea lines, homozygous by the allele sym^2A), are characterized by a less compact location of the sym-genes than the strains lacking the nodX gene. The size of the symbiotic cluster in the strains possessing nodX was 94.5 ± 3.5 kb, with the share of the sym-genes of 36.5 ± 1.5%, while for the strains lacking nodX these values were 61.7 ± 3.7 kb and 56.3 ± 1.4%, respectively (significant difference at P ₀ < 0.01). Syntenic structures were revealed in the symbiotic regions of strains Vaf12, UPM1131, and TOM, as well as syntenic structures of non-symbiotic regions in strains Vaf12, TOM, and WSM1689. The correlation coefficients between the matrices of genetic distances in the analyzed strains for the nodABC, nifHDK, and fixABC operons were on average 0.993 ± 0.002, while their values for the plasmid sites located between the sym-genes were considerably less (0.706 ± 0.010). In these regions, 21 to 27% of the genes were involved in amino acid transport and metabolism, which was substantially higher than the average for the genome of R. leguminosarum bv. viciae (11–12%). These data suggest that the evolution of R. leguminosarum bv. viciae, defined by narrowing of the host specificity (associated with a loss of the nodX gene), was accompanied by reduction of the regions of plasmids located between the sym-genes, as well as by specialization of these areas to perform the functions related to symbiotic nitrogen fixation. The observed increase of density in the cluster of sym-genes may be associated with intensification of their horizontal transfer in the populations of rhizobia, which determines the speed of evolution of the symbiotic system.     

Late Cretaceous (Santonian-Campanian) sea lilies (Echinodermata,Crinoidea) from the glacial rafts of northwestern Poland

Seven Santonian (Isocrinus? minutus, Tetracrinus jagti, Cyathidium senessei, Bourgueticrinidae indet., Notocrinidae indet., Glenotremites paradoxus, Marsupites testudinarius) and seven Campanian (Nielsenicrinus carinatus, Austinocrinus sp., Bourgueticrinidae indet., Bourgueticrinus cf. constrictus, B. ellipticus, B.? suedicus, Roveacrinina gen. et sp. indet.) crinoid taxa from the Cretaceous glacial rafts of northwestern Poland (near Wolin Island) are described for the first time. The taphonomy and palaeogeographic implications are discussed. The present assemblage differs taxonomically from the crinoid faunules recently described from the glacial rafts of eastern Poland. However, these faunules are similar to crinoids from the autochthonous Upper Cretaceous sediments of southern and eastern Poland (Miechów Trough, Kraków-Cz?stochowa Upland, Middle Vistula River valley). An update of Late Cretaceous crinoids from the Miechów Trough and Kraków-Cz?stochowa Upland is also given.     

The Psilostomidae Looss, 1900 (<Emphasis Type="Italic">sensu stricto</Emphasis>) (Digenea: Echinostomatoidea): description of three new genera and a key to the genera of the family

Three new psilostomid genera, Byrdtrema n. g., Longisaccus n. g. and Macracetabulum n. g., each with a single species, are described from ducks, Aix sponsa (L.) and Bucephala albeola (L.) in North America. Byrdtrema n. g. and Macracetabulum n. g. possess a bipartite seminal vesicle and share this character with four psilostomid genera, Grysoma Byrd, Bogitsh & Maples, 1961, Neopsilotrema Kudlai, Pulis, Kostadinova & Tkach, 2016, Psilostomum Looss, 1899 and Psilotornus Byrd & Prestwood, 1969. Byrdtrema n. g. differs from Macracetabulum n. g. in the shape of the body (elongate vs elongate-oval); the position of the ventral sucker (in first third of body vs just pre-equatorial); the shorter forebody; as well as in the smaller size of the eggs in relation to body length. Both new genera differ from (i) Grysoma by the nature of the vitellarium (large, compact follicles with small vitelline cells vs weakly defined follicles with large vitelline cells, respectively) and the smaller size of the eggs in relation to body length; (ii) Psilostomum in the posterior extend of the cirrus-sac in relation to ventral sucker (slightly posterior vs more posterior), the location of the genital pore (at the level of oesophagus vs just postbifurcal), the shorter length of uterine and longer post-testicular fields in relation to body length, and the anterior limits of vitellarium (at the level of ventral sucker vs posterior to ventral sucker); (iii) Psilotornus by the presence of a muscular pharynx (vs absent or rudimentary) and the location of the cirrus-sac (antero-dorsal to ventral sucker or more posterior vs entirely anterior to ventral sucker) and ovary (in hindbody vs in forebody). Byrdtrema n. g. differs from Neopsilotrema in the shape of the body (elongate vs subspherical to elongate-oval) and ventral sucker (elongate-oval vs subspherical to transversely oval), the shorter forebody and smaller eggs in relation to body length. Macracetabulum n. g. differs from Neopsilotrema by the shape of the ventral sucker (elongate-oval vs subspherical to transversely oval), the anterior limits of vitellarium (level of middle of ventral sucker vs level of intestinal bifurcation or anterior testis); and the slightly smaller size of eggs in relation to body length. Among the psilostomid genera, Longisaccus n. g. shows close affinities to Psilochasmus Lühe, 1909 in the presence of the long cirrus-sac and tubular internal seminal vesicle but can be clearly distinguished from the latter by the absence of the retractile tail-like process. In combination with molecular data, the above differences justify the recognition of three new genera. A key to the genera of the Psilostomidae is provided.     

Middle Givetian echinoderms from the Schlade Valley (Rhenish Massif,Germany): habitats,taxonomy and ecostratigraphy

Crinoids and ophiocistioids from classical fossil localities of the National Geosite “Schlade Valley”, NE of Bergisch Gladbach (Germany) are reported for the first time. The fossils were derived from the reefal Büchel Formation (lowermost Middle Givetian, Middle Devonian) at the northern flank of the Bergisch Gladbach-Paffrath Syncline (eastern Rhenish Massif). From the abandoned quarry “Im Grubenfeld”, skeletal elements of holothuroids, ophiocistioids and crinoids are documented from a bituminous marly shale horizon in the middle Büchel Formation. The finely bedded shales suffocated an already stressed, muddy “reefal” fauna, which followed on top of a massive Actinostroma stromatoporoid biostrome. The shales characterise an apparently regionally occurring event, herein denominated as “Schlade Event”. It is considered to represent the climax of the transgressive Lower pumilio Event. The autochthonous and vagile epibenthic echinoderm fauna on top of the “Schlade Event Layer” is low diverse. It is regarded, herein, as post disaster fauna, recolonising the dysaerobic softground/soupground together with the well-adapted trilobite Goldius. The cupressocrinitids Halocrinites and Procupressocrinus were recognised from a younger stratum of the upper Büchel Formation within the abandoned “Zimmermann Quarry” near-by. The crinoids settled in high-energy environments of a reef flat in association with characteristic brachiopods (Uncites, Stringocephalus) and bivalves (Eomegalodon) and were swept by storms into reef flat pools. In those exceptional fossil lagerstätten, which are marl-filled obrution deposits, they were parautochthonously preserved together with an autochthonous fauna composed mostly of gastropods and extremely rare allochthonous biota from the open marine realm. Published biozonations of the Büchel Formation, especially on ammonoids, are evaluated, partly corrected and supplemented by ecostratigraphic associations of rugose corals and crinoids. Schlade Event below and Taghanic Event above are major factors controlling biozonation. Taxonomic notes concern revision of the holothuroids from the Schlade Valley and discussion of taxonomic attribution of ophiocistoids and crinoids. All species formerly included in “Abbreviatocrinites” are transferred to genus Halocrinites, which has priority.     

Nodal and BMP expression during the transition to pentamery in the sea urchin <Emphasis Type="Italic">Heliocidaris erythrogramma</Emphasis>: insights into patterning the enigmatic echinoderm body plan

Background

The molecular mechanisms underlying the development of the unusual echinoderm pentameral body plan and their likeness to mechanisms underlying the development of the bilateral plans of other deuterostomes are of interest in tracing body plan evolution. In this first study of the spatial expression of genes associated with Nodal and BMP2/4 signalling during the transition to pentamery in sea urchins, we investigate Heliocidaris erythrogramma, a species that provides access to the developing adult rudiment within days of fertilization.

Results

BMP2/4, and the putative downstream genes, Six1/2, Eya, Tbx2/3 and Msx were expressed in the earliest morphological manifestation of pentamery during development, the five hydrocoele lobes. The formation of the vestibular ectoderm, the specialized region overlying the left coelom that forms adult ectoderm, involved the expression of putative Nodal target genes Chordin, Gsc and BMP2/4 and putative BMP2/4 target genes Dlx, Msx and Tbx. The expression of Nodal, Lefty and Pitx2 in the right ectoderm, and Pitx2 in the right coelom, was as previously observed in other sea urchins.

Conclusion

That genes associated with Nodal and BMP2/4 signalling are expressed in the hydrocoele lobes, indicates that they have a role in the developmental transition to pentamery, contributing to our understanding of how the most unusual body plan in the Bilateria may have evolved. We suggest that the Nodal and BMP2/4 signalling cascades might have been duplicated or split during the evolution to pentamery.

     

Specific features of eye regeneration in multiocular planarians <Emphasis Type="Italic">Polycelis tenuis</Emphasis>

Regeneration and negative phototaxis were studied in planarians Polycelis tenuis, in which the anterior body end is fringed with many eyes. Comparative data for the same indices are given for binocular planarians Girardia tigrina. Multiple eyes regenerated gradually with a decrease in the rate of regeneration and independently from the rate of restoration of the anterior body end, where they are located. Negative phototaxis was restored independently from the total amount of regenerated eyes. It was unstable in both planarian species.     

Aboral nervous system in two Ordovician crinoids: Reconstruction and comparison of Baltic <Emphasis Type="Italic">Pentamerocrinus</Emphasis> Jaekel and <Emphasis Type="Italic">Grammocrinus</Emphasis> Eichwald

Two unusual Middle Ordovician crinoid genera from the St. Petersburg Region, Pentamerocrinus Jaekel, 1918 and Grammocrinus Eichwald, 1860, are redescribed. A new species, Pentamerocrinus kosovi sp. nov., is described based on new material and the cup structure in the type species Grammocrinus lineatus, which has previously been known only from stem fragments, is reconstructed. The system of ridges and canals on the internal surface of the cup plates in both genera is described, allowing the reconstruction of the aboral nervous system. It is in general similar to extant crinoids, but the two Ordovician genera differ considerably in structural details. In Pentamerocrinus, ten nerve cords diverge interradially from the ganglionated nerve ring at the cup base and soon are fused in pairs inside the rays. In Grammocrinus, a similar nerve ring also gives rise to ten cords, but they are inside the rays and become fused in the interrays. This distinction in morphology of the nervous systems is correlated with the interradial arrangement of the axial canal angles of the stem in the first case and radial in the second. Therefore, despite general similarity in the structure and arrangement of calyceal plates, the genus Grammocrinus is assigned to the disparid crinoid family Iocrinidae, while the monotypic family Pentamerocrinidae Jaekel, 1918 is regarded as a fam. inc. sed. of inadunate crinoids.     

Soft Bottom Communities in Marine Lakes Sisjajarvi and Linjalampi (Barents Sea)

Based on the data of benthic surveys of 2010–2012, three benthic communities: a shallow-water community with the dominance of Scoloplos spp., Nucula tennuis, and Scalibregma inflatum; a deep-water community with the dominance of Chaetosone sp.; and a community of mixed sediments, have been distinguished in soft sediments in marine lakes Sisjajarvi and Linjalampi. These communities are typically marine and similar to other communities in shallow areas of the Barents Sea. They mostly differ in a high abundance of the polychaete Scalibregma inflatum and a small number of echinoderms from the communities in other bays of the Barents Sea. The abundance of the polychaete S. inflatum indicates indirectly possible cases of anoxia in Lake Sisjajarvi.     

Morphological and Molecular Analysis of Isolated Cultures of Tobacco Adventitious Roots Obtained by the Methods of Biolistic Bombardment and <Emphasis Type="Italic">Agrobacterium</Emphasis>-Mediated Transformation

Plant infection with Agrobacterium rhizogenes leads to the development of a hairy root disease notable for the rapid agravitropic growth of roots on hormone-free nutrient media. In order to look into the interaction of A. rhizogenes with plants and assess opportunities of practical application of hairy root culture, new approaches to their production are elaborated. A method of bacterium-free and plasmid-free production of genetically modified roots (hairy roots) by means of biolistic transformation of leaf explants with a DNA fragment (size of 5461 bp) consisting of genes rolA, rolB, rolC, and rolD are proposed. In most cases, such transformation resulted in the emergence of only adventitious roots with transient expression of rol-genes, and the growth of such roots on hormone-free media ceased in 2–3 months in contrast to genuine hairy roots capable of unrestricted growth. Molecular analysis of different systems of target genes’ expression showed an important role of transgene rolC and host gene of cyclin-dependent protein kinase CDKB1-1 in the maintenance of rapid growth of hairy roots in vitro (in isolated cultures).     

<Emphasis Type="Italic">Adlardia</Emphasis><Emphasis Type="Italic">novaecaledoniae</Emphasis> n. g., n. sp. (Digenea: Cryptogonimidae) from the fork-tailed threadfin bream <Emphasis Type="Italic">Nemipterus furcosus</Emphasis> (Val.) (Perciformes: Nemipteridae) off New Caledonia

Adlardia novaecaledoniae n. g., n. sp. (Digenea: Cryptogonimidae) is described from the fish Nemipterus furcosus (Val.) (Perciformes: Nemipteridae) from off New Caledonia (South Pacific). Adlardia n. g. is distinguished from all other cryptogonimid genera by the combination of an elongate body, the presence of oral spines, intestinal caeca that open via ani at the posterior end of the body, a highly lobed ovary, oblique testes that are located in the mid-hindbody, vitelline follicles that extend from midway between the testes and ovary to midway between the ovary and ventral sucker, and an excretory vesicle that bifurcates dorsal to the ovary and reunites immediately anterior to the pharynx. A. novaecaledoniae n. sp. is the only cryptogonimid that has been reported with an excretory vesicle that reunites anterior to the pharynx. Siphoderina elongata (Gu &; Shen, 1979) Miller &; Cribb, 2008 is transferred to Adlardia as A. elongata (Gu &; Shen, 1979) n. comb. based on morphological and ecological (host group) agreement with A. novaecaledoniae. Bayesian inference analysis of LSU rDNA revealed that A. novaecaledoniae nested well within a clade containing cryptogonimid taxa known almost exclusively from haemulid and lutjanid fishes, suggesting that host-switching between teleosts of the Haemuloidea, Lutjanoidea and Sparoidea may have been common in the evolutionary history of this system.     

New species of the oribatid mite genus <Emphasis Type="Italic">Galumnella</Emphasis> Berlese, 1916 (Acari,Oribatida, Galumnellidae) from the Philippines

Two new species of the oribatid mite genus Galumnella (Oribatida, Galumnellidae) are described from the Philippines. Galumnella processa sp. n. differs from G. junichiaokii Ermilov, Corpuz-Raros et Shimano, 2014 in a triangular process on the anterior margin of the ventral plate and in smooth bothridial setae. Galumnella quezonensis sp. n. differs from G. cellularis Balogh et Mahunka, 1967 in a larger body and in the presence of bothridial setae with very long and thin apices and of longitudinal ridges in the anogenital region.     

<Emphasis Type="Italic">Angiostoma norvegicum</Emphasis> n. sp. (Nematoda: Angiostomatidae) a parasite of arionid slugs in Norway

Angiostoma norvegicum n. sp. (Angiostomatidae) is described from the oesophagus, crop and the buccal mass of five species of slugs of the family Arionidae, Arion vulgaris (Moquin-Tandon), Arion ater (L.), Arion fasciatus (Nilsson), Arion fuscus (Müller) and Arion rufus/Arion ater hybrid), collected throughout Norway. Angiostoma norvegicum n. sp. was found parasitising arionids at seven of the 30 sample sites examined (23.3%), and 9.9% of all Arion spp. were infected with this nematode. The new species is characterised by its large size (4.0–8.6 mm long) and in having: lateral alae; 6 + 6 papillae at the cephalic end; a large circular mouth aperture; a spacious stoma; a pharyngeal basal bulb without valvular apparatus; an excretory pore near the base of bulb; a distal part of posterior ovary always outstretched; an anterior ovary distally nearly always outstretched; a vulva situated anterior to mid-body; long, nearly straight spicules and a small gubernaculum; three circumcloacal papillae and caudal genital papillae (GP) arranged in a pattern 1+2/3+3 with GP 5 and GP 8 opened on dorsal side of narrow bursa not reaching tail tip; short conical tails in both sexes with tips supplied by 4 short, unequal denticles. Morphologically, A. norvegicum n. sp. is similar to Angiostoma limacis Dujardin, 1845, which diagnostic characteristics are given based on examination of specimens from Norway and the UK. Conversely, the phylogenetic analyses based on D2D3 large subunit (LSU) rRNA gene sequences performed in the present study did not support the morphological affinity of these two species. Phylogenetic analyses demonstrated that although Angiostoma spp. cluster together, A. norvegicum n. sp. forms a tight monophyletic clade with the milacid nematode parasites Angiostoma margaretae Ross, Malan & Ivanova, 2011 and Angiostoma milacis Ivanova & Wilson, 2009.     

Heterobucephalopsine and prosorhynchine trematodes (Digenea: Bucephalidae) from teleost fishes of Moreton Bay,Queensland, Australia,with the description of two new species

Eight species of the trematode family Bucephalidae Poche, 1907 are reported from teleost fishes in Moreton Bay, Queensland, Australia. Heterobucephalopsis yongi n. sp. is described from Gymnothorax eurostus (Muraenidae); the new form is distinguished from its congeners in the possession of a tiny cirrus-sac relative to body length, the length of the caecum, the position of the mouth and pharynx, and the position of the testes and ovary. Two known species of Dollfustrema Eckmann, 1934, D. durum Nolan, Curran, Miller, Cutmore, Cantacessi & Cribb, 2015 and D. gibsoni Nolan & Cribb, 2010, are reported from Gymnothorax pseudothyrsoideus (Bleeker) (Muraenidae); although both species were described from Australian waters, this represents the first reports from Moreton Bay and G. pseudothyrsoideus. Four species of Prosorhynchus Odhner, 1905 are reported, including one new, P. brayi n. sp., which is described from Epinephelus coioides (Hamilton) (Serranidae); P. brayi n. sp. is distinguished from its congeners in the possession of vitelline follicles in a confluent arc distinctly posterior to a conical rhynchus, uterine coils that do not extend anterior to the vitelline arc, contiguous testes, a cirrus-sac that reaches anteriorly to at least the level of the posterior testis and a short excretory vesicle. Three known species of Prosorhynchus are reported from Australia, for the first time: P. luzonicus Velasquez, 1959 and P. maternus Bray & Justine, 2006 from E. coioides and Prosorhynchus platycephali (Yamaguti, 1934) Srivastava, 1938 from Ambiserrula jugosa (McCulloch) and Inegocia japonica (Cuvier) (Platycephalidae). Skrjabiniella Issaitschikow, 1928 is re-recognised for new specimens of Skrjabiniella uniporus (Ozaki, 1924) n. comb. collected from Conger cinereus Rüppell (Congridae); three additional species of Prosorhynchus are considered members of this genus, two of which are synonymised with S. uniporus.     

Invasion of Japan by exotic leafminers <Emphasis Type="Italic">Liriomyza</Emphasis> spp. (Diptera: Agromyzidae) and its consequences

Identifying patterns and causes of species displacement is important from the viewpoints of ecology and evolutionary biology as this phenomenon affects community structure. Here I review the species displacement between Liriomyza trifolii (Burgess) and Liriomyza sativae Blanchard (Diptera: Agromyzidae) in Japan. These two species and Liriomyza huidobrensis (Blanchard) originated from the New World and are considered to have invaded Japan from around 1990 to the early 2000s. During this period, L. trifolii was apparently displaced by L. sativae, but the direction of displacement in Japan has been contrary to that observed between the same two species in the USA and China. While the displacement of L. sativae by L. trifolii in these two countries can be attributed to the lower insecticide susceptibility of L. trifolii there, species displacement in the opposite direction in Japan is probably due to the relatively high fecundity of L. sativae and differential effects of the introduced parasitoid Dacnusa sibirica Telenga (Hymenoptera: Braconidae) on both Liriomyza species, except in the south of the country.     

New scarab-beetle species (Coleoptera,Scarabaeidae, Aphodiinae,Orphninae) from Central Asia and Southern Africa

Three new scarab-beetle species are described. Aphodius moronensis sp. n. (northern Mongolia) and A. kozlovi sp. n (eastern Tibet) with modified spurs on fore tibiae in males are placed in the falcispinis group of the subgenus Agolius but are similar to the grafi group of the subgenus Chilothorax in the shape of parameres and elytral pattern. The new species differ from A. falcispinis in the shape of the spur; A. moronensis sp. n. also differs in the shape of the body and parameres. Orphnus transvaalensis sp. n. is the second apterous Orphnus species found in Southern Africa. It differs from the closely related O. harrisoni in the shape of parameres, position of the hornlike clypeal process, and in a smaller body size.     

Some features of the biology and composition of the diet of the rock lobster <Emphasis Type="Italic">Acantharctus posteli</Emphasis> (Decapoda,Crustacea, Scyllarinae) (West Africa)

Acantharctus posteli (Crustacea, Decapoda, Achelata, Scyllarinae) belongs to the old relic circumtropical genus of mainly upper shelf rock lobsters. It is an endemic species of the West African tropical zoogeographic region with its distribution between the cape of Cap Blanc (21°40′ N) to the north and the mouth of the Congo River to the south (approximately 4° S). The length of the studied rock lobsters ranges from 10 to 80 mm. Males are slightly smaller than females. The smallest size of ovigerous females was 29 mm. The life cycle of A. posteli appears to be about 2 years. The stomach contents of 43 specimens ranging in size from 42 to 68 mm from the waters of the Republic of Sierra Leone were analyzed. Rock lobsters consume mainly detritus that includes benthic foraminifera. In addition, fish, echinoderms, mollusks, and decapods are secondary prey items. The mean Froerman coefficient of 3.96 allows suggesting that A. posteli can be characterized as a predator-collector, which is similar to rock lobsters of the genera Jasus and Projasus.