丛枝菌根真菌响应桉树茄科雷尔氏菌侵染进程基因的筛选与鉴定

【背景】桉树(Eucalyptus)青枯病危害严重,丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)与桉树共生影响桉树对青枯病的抗性,而AMF响应桉树青枯菌侵染的机制仍不清楚。【目的】探索AMF响应桉树茄科雷尔氏菌(Ralstonia solanacearum)的侵染机制。【方法】以非菌根化和异形根孢囊霉(Rhizophagus irregularis)菌根化巨桉(Eucalyptus grandis)分别受茄科雷尔氏菌侵染0、24、48和96 h接种后(hour post-inoculated, hpi)的根系组织为研究对象,基于转录组测序筛选和鉴定菌根化巨桉根系中异形根孢囊霉响应茄科雷尔氏菌侵染的基因信息。【结果】与对应非菌根化桉树受茄科雷尔氏菌侵染的时间点相比,菌根化桉树中异形根孢囊霉响应青枯菌侵染显著差异表达基因为3 382–5 989个,随青枯侵染时间进程的增加,异形根孢囊霉特异性响应茄科雷尔氏菌侵染差异表达基因数量逐渐增多。茄科雷尔氏菌侵染24 hpi时,异形根孢囊霉显著富集共生体生长、孢子形成和凋亡信号通路、铁载体等相关基因;茄科雷尔氏菌侵...     

Disentangling the role of hybridization in the evolution of the endangered Arizona cliffrose (<Emphasis Type="Italic">Purshia subintegra</Emphasis>; Rosaceae): a molecular and morphological analysis

Hybridization may threaten the conservation status of rare species through genetic assimilation and may confound the ability to distinguish among taxa. We studied these issues in an endangered shrub, Purshia subintegra (Rosaceae), known from four populations growing on limestone outcrops in central Arizona (USA). Using amplified fragment length polymorphisms (AFLP) and the Bayesian clustering algorithm implemented in STRUCTURE, we identified three distinct genetic lineages among Arizona Purshia subintegra and P. stansburiana. An initial split divided San Carlos Basin P. subintegra (considered P. pinkavae by Schaack) from northern P. stansburiana populations (F_ST = 0.394). A subsequent split separated northern P. stansburiana from two P. subintegra populations at Horseshoe Lake and Burro Creek (F_ST = 0.207), which comprised a nearly perfect admixture of the two lineages identified in the initial analysis. In the Verde River Valley P. subintegra is sympatric with P. stansburiana and exhibited an average 27% P. stansburiana genes for 5 of 6 stands analyzed, indicating ongoing hybridization and backcrossing with P. subintegra. Individuals carrying >90% P. subintegra markers are identifiable 68% of the time based on morphology, with leaf lobing, leaf size, and leaf length acting as the most reliable indicators of taxonomic status. However, the genetic and morphological distance correlation among individuals was low (r = 0.17, P = 0.0002), indicating that morphology cannot always accurately predict genetic admixture or taxonomy. Overall, our study confirmed the genetic distinctiveness of the San Carlos Basin population, an ancient natural hybrid origin of P. subintegra, and the presence of a hybrid swarm in the Verde Valley, whose conservation value may lie in its heightened genetic diversity.     

Functional compatibility in cucumber mycorrhizas in terms of plant growth performance and foliar nutrient composition

Functional compatibility in cucumber mycorrhizas in terms of plant and fungal growth, and foliar nutrient composition from all possible combinations of six cucumber varieties and three species of arbuscular mycorrhizal (AM) fungi was evaluated. Measurements of foliar nutrient composition included N, P, K, Mg, Ca, Na, Fe, Zn, Mn and Cu. Growth of AM fungi was measured in terms of root colonisation, as examined with microscopy and the AM fungus biomarker fatty acid 16:1ω5 from both phospholipids and neutral lipids. Different responses of plant growth and foliar nutrient profiles were observed for the different AM symbioses examined. The AM fungus Claroideoglomus claroideum caused growth depression in association with four out of six cucumber varieties; Rhizophagus irregularis caused growth promotion in one of six cucumber varieties; whereas Funneliformis mosseae had no effect on the growth performance of any of the cucumber varieties examined. All three AM fungi markedly altered host plant shoot nutrient composition, with the strongest contrast observed between cucumber–R. irregularis symbioses and non‐mycorrhizal cucumber plants, independent of cucumber variety. On the other hand, AM fungal growth in roots differed between the three AM fungi, but was unaffected by host genotype. Strong build‐up of storage lipids was observed for R. irregularis, which was more moderate in the two other AM fungi. In conclusion, strong differential responses of cucumber varieties to inoculation with different AM fungi in terms of growth and shoot nutrient composition revealed high functional diversity in AM symbioses in cucumber plants.     

Opening the black box: outcomes of interactions between arbuscular mycorrhizal (AM) and non‐host genotypes of Medicago depend on fungal identity,interplay between P uptake pathways and external P supply

We investigated the physiology that underlies the influence of arbuscular mycorrhizal (AM) colonization on outcomes of interactions between plants. We grew Medicago truncatula A17 and its AM‐defective mutant dmi1 in intragenotypic (two plants per pot of the same genotype, x2) or intergenotypic (one plant of each genotype, 1 + 1) combinations, inoculated or not with Rhizophagus irregularis (formerly Glomus intraradices) or Gigaspora margarita. We measured plant growth, colonization, contributions of AM and direct P uptake pathways using ³²P, and expression of plant P_i transporter genes at two levels of P supply. A17 (x2) responded positively to inoculation only at low P. The response was enhanced with 1 + 1 even at high P where colonization in A17 was reduced. With R. irregularis P uptake by the AM pathway was unaffected by P supply, whereas with G. margarita, the AM pathway was lower at high P, and direct uptake higher. Gene expression varied and was unrelated to P uptake through the two pathways. There was no evidence of plant control of P uptake via R. irregularis at high P but there was via G. margarita. Importantly, growth responses of plant genotypes grown alone did not predict outcomes of intergenotypic interactions.     

Genetic relatedness among worker nestmates of three formicine slave-making ants

Summary We estimated genetic relatedness among worker nestmates of the facultative slave-making antFormica subnuda (28 colonies), and the obligate slavemakers F. subintegra (19 colonies) andPolyergus breviceps (14 colonies) using horizontal starch gel electrophoresis. Relatedness among nestmates was 0.42 inF. subnuda, 0.70 inF. subintegra, and 0.49 inP. breviceps on average. Relatedness ofF. subintegra workers did not differ significantly from 0.75 indicating that this species is monogynous, though some females may mate multiply. The estimates ofF. subnuda andP. breviceps were significantly lower than 0.75 and, consequently, colonies were polygynous and/or poly-androus. The inbreeding coefficients were close to zero in all species suggesting random mating. We suggest that owing to practical monogyny and obligate nature of its slavemaking,F. subintegra is a good species for tests of sex allocation theory.     

Flower morphology and relationships of Schefflera subintegra (Araliaceae,Apiales): an evolutionary step towards extreme floral polymery

Gross morphology and the development of flowers in Schefflera subintegra (Araliaceae) are examined. The floral groundplan of this species is found to be very similar to that of Tupidanthus calyptratus representing a case of most extreme floral polymery within Araliaceae. Schefflera subintegra differs from T. calyptratus with respect to a lower floral merism (19–43 versus 60–172 stamens and 15–33 versus 60–138 carpels respectively) and by transformation from polysymmetry to disymmetry of flower in the course of its development. Close relationships between S. subintegra, T. calyptratus, and Schefflera hemiepiphytica have been confirmed by phylogenetic analysis based on nuclear ribosomal internal transcribed spacer sequences. These species form a subclade within the Asian Schefflera clade, with T. calyptratus as a sister taxon to two other species. Apart from more or less pronounced floral polymery, the species of this subclade share calyx and corolla without any traits of individual sepals and petals, and also a massive calyptra. As these data suggest, the extremely polymerous flowers of Tupidanthus apparently evolved in two steps: (1) the saltational multiplication of floral elements together with a loss of individuality of sepals in the calyx and petals in the corolla and (2) further polymerization of androecium and gynoecium. Mutation(s) in CLAVATA‐like gene(s) are suggested as a possible mechanism of the saltation event. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 553–597.     

Micropropagation of Cowania subintegra and Cowania stansburiana

Both Cowania subintegra Kearney and C. stansburiana Torr. were successfully propagated in vitro. Shoot proliferation occurred from shoot tips of green-house grown C. subintegra using a modified Murashige and Skoog medium supplemented with 4.4 M 6-benzyladenine and 0.5 M indole butyric acid. Excised microshoots (1.5–3.0 cm long) of both species were rooted using a two-step process in which they were cultured for 3 days in a root initiation medium with 2.7 M naphthaleneacetic acid and then transferred to a low nitrogen root elongation medium without auxin. Plantlets were successfully transferred to soilless potting mix.     

The formation and development of cellulose-synthesizing linear terminal complexes (TCs) in the plasma membrane of the marine red algaErythrocladia subintegra Rosenv.

Summary The formation and development of linear terminal complexes (TCs), the putative cellulose synthesizing units of the red algaErythrocladia subintegra Rosenv., were investigated by a freeze etching technique using both rotary and unidirectional shadowing. The ribbon-like cellulose fibrils ofE. subintegra are 27.6 ± 0.8 nm wide and only 1–1.5 nm thick. They are synthesized by TCs which are composed of repeating transverse rows formed of four particles, the TC subunits. About 50.4 ± 1.7 subunits constitute a TC. They are apparently more strongly interconnected in transverse than in longitudinal directions. Some TC subunits can be resolved as doublets by Fourier analysis. Large globular particles (globules) seem to function as precursor units in the assembly and maturation of the TCs. They are composed of a central hole (the core) with small subunits forming a peripheral ridge and seem to represent zymogenic precursors. TC assembly is initiated after two or three gobules come into close contact with each other, swell and unfold to a nucleation unit resembling the first 2–3 transverse rows of a TC. Longitudinal elongation of the TC occurs by the unfolding of globules attached to both ends of the TC nucleation unit until the TC is completed. The typical intramembranous particles observed inErythrocladia (unidirectional shadowing) are 9.15 ± 0.13 nm in diameter, whereas those of a TC have an average diameter of 8.77 ± 0.11 nm. During cell wall synthesis membranes of vesicles originating from the Golgi apparatus and which seem to fuse with the plasma membrane contain large globules, 15–22 nm in diameter, as well as tetrads with a particle diameter of about 8 nm. The latter are assumed to be involved in the synthesis of the amorphous extracellular matrix cell wall polysaccharides. The following working model for cellulose fibril assembly inE. subintegra is suggested: (1) the ribbon-like cellulose fibril is synthesized by a single linear TC; (2) the number of glucan chains per microfibril correlates with the number of TC subunits; (3) a single subunit synthesizes 3 glucan chains which appear to stack along the 0.6 nm lattice plane; (4) lateral aggregation of the 3-mer stacks leads to the crystalline microfibril.Dedicated to Prof. Dr. Dr. h.c. Eberhard Schnepf on the occasion of his retirement     

Arbuscular mycorrhizal fungi reduce growth and infect roots of the non‐host plant Arabidopsis thaliana

The arbuscular mycorrhizal (AM) symbiosis is widespread throughout the plant kingdom and important for plant nutrition and ecosystem functioning. Nonetheless, most terrestrial ecosystems also contain a considerable number of non‐mycorrhizal plants. The interaction of such non‐host plants with AM fungi (AMF) is still poorly understood. Here, in three complementary experiments, we investigated whether the non‐mycorrhizal plant Arabidopsis thaliana, the model organism for plant molecular biology and genetics, interacts with AMF. We grew A. thaliana alone or together with a mycorrhizal host species (either Trifolium pratense or Lolium multiflorum) in the presence or absence of the AMF Rhizophagus irregularis. Plants were grown in a dual‐compartment system with a hyphal mesh separating roots of A. thaliana from roots of the host species, avoiding direct root competition. The host plants in the system ensured the presence of an active AM fungal network. AM fungal networks caused growth depressions in A. thaliana of more than 50% which were not observed in the absence of host plants. Microscopy analyses revealed that R. irregularis supported by a host plant was capable of infecting A. thaliana root tissues (up to 43% of root length colonized), but no arbuscules were observed. The results reveal high susceptibility of A. thaliana to R. irregularis, suggesting that A. thaliana is a suitable model plant to study non‐host/AMF interactions and the biological basis of AM incompatibility.     

Effects of dual inoculation of mycorrhiza and endophytic,rhizospheric or parasitic bacteria on the root-knot nematode disease of tomato

The effects of mycorrhisation and inoculation with soil bacteria on the disease caused by Meloidogyne incognita on tomato were studied in pots under greenhouse conditions. Efficacy in promoting plant growth and reducing disease severity and final nematode densities were evaluated for two arbuscular mycorrhizal fungi (AMF; Funneliformis mosseae and Rhizophagus irregularis), three soil bacteria with different living strategies (the endophyte Bacillus megaterium, a rhizospheric Pseudomonas putida and the hyperparasite of nematodes Pasteuria penetrans) and combinations of the fungi and bacteria. In M. incognita-infested plants, F. mosseae increased tomato growth more than R. irregularis, and plants inoculated with B. megaterium presented higher shoot fresh weight than with P. putida or P. penetrans, but dual inoculation did not improve tomato growth more than single inoculations. Disease severity and final nematode densities were reduced by F. mosseae compared to non-mycorrhizal plants. B. megaterium and P. penetrans reduced both the root galling and the final nematode densities compared to treatments without bacteria. P. penetrans reduced final nematode densities more than B. megaterium or P. putida. Dual inoculation of AMF and P. penetrans showed the highest efficacy in reducing the final nematode densities in tomato.     

LIGHT BOUNDARIES AND THE COUPLED EFFECTS OF SURFACE HYDROPHOBICITY AND LIGHT ON SPORE SETTLEMENT IN THE BROWN ALGA HINCKSIA IRREGULARIS (PHAEOPHYCEAE) 1

We examined the effects of light and surface hydrophobicity individually and in tandem on Hincksia irregularis (Kützing) Amsler spore settlement. Hincksia irregularis spores were determined to be negatively phototactic by the use of computer‐assisted motion analysis. Spore settlement was significantly influenced by surface hydrophobicity and by light, individually and in tandem. Experiments conducted using culture plates modified to reduce well edge artifacts revealed significantly higher settlement on hydrophobic surfaces and in dark environments when compared with negatively charged surfaces and lighted environments. Experimental light/dark boundaries elicited distinct spore settlement responses, with spores displaying dissimilar settlement patterns on plates with different surface hydrophobicities. The results of this study indicate H. irregularis spores possess the capacity for complex responses to their environment. These complex responses may influence dispersal and aid spores in the detection of suitable settlement locations in marine microenvironments.     

New records and a bibliography of the mosses of Pakistan

Abstract

Forty mosses are recorded for Pakistan, of which six appear to be new records for that country. Timmiella subintegra Dix. is reduced to synonymy under T. barbuloides (Brid.) Moenk., and there are notes on the typification of Pilotrichum pluvinii Brid. (Cryptoleptodon pluvinii (Brid.) Broth.).     

Are Ichthyosporea animals or fungi? Bayesian phylogenetic analysis of elongation factor 1α of Ichthyophonus irregularis

Ichthyosporea is a recently recognized group of morphologically simple eukaryotes, many of which cause disease in aquatic organisms. Ribosomal RNA sequence analyses place Ichthyosporea near the divergence of the animal and fungal lineages, but do not allow resolution of its exact phylogenetic position. Some of the best evidence for a specific grouping of animals and fungi (Opisthokonta) has come from elongation factor 1α, not only phylogenetic analysis of sequences but also the presence or absence of short insertions and deletions. We sequenced the EF-1α gene from the ichthyosporean parasite Ichthyophonus irregularis and determined its phylogenetic position using neighbor-joining, parsimony and Bayesian methods. We also sequenced EF-1α genes from four chytrids to provide broader representation within fungi. Sequence analyses and the presence of a characteristic 12 amino acid insertion strongly indicate that I. irregularis is a member of Opisthokonta, but do not resolve whether I. irregularis is a specific relative of animals or of fungi. However, the EF-1α of I. irregularis exhibits a two amino acid deletion heretofore reported only among fungi.     

Morphological and genetic differentiation of Eremina desertorum (Gastropoda,Pulmonata, Helicidae) in Egypt

To understand the processes that result in morphological and genetic diversity, we studied the differentiation of the land snails Eremina d. desertorum and Eremina desertorum irregularis in the deserts of northern Egypt. These two taxa are differentiated with regard to shell size and shape and are separated by a narrow hybrid zone west of Alexandria. The lack of differences in the genitalia and the lack of reciprocal monophyly of the mitochondrial haplotypes of E. d. desertorum and E. desertorum irregularis support their classification as subspecies rather than distinct species. Low genetic distances indicate that the differentiation is probably less than half a million years old. The genetic data indicate a population expansion in agreement with other evidence that the Nile region in northern Egypt was more humid well into historical times than today. Shell size and shape are correlated with a climatic gradient from cooler and more humid conditions along the Mediterranean coast to arid and hot conditions in the interior. The decrease of body size with decreasing precipitation and increasing temperature might be explained by limited time for food intake in the more arid regions. The shape differences between the taxa are partly an indirect consequence of selection for body size, but are also directly affected by selection for reduction of aperture size.     

Relationship between genetic variability in Rhizophagus irregularis and tolerance to saline conditions

Reclamation of saline soils produced by extraction of bitumen from oil sands is challenging. The main objective of this study was to select a salt-tolerant arbuscular mycorrhizal (AM) fungal isolate that could, in the future, be used to pre-inoculate plants used in reclamation of saline substrates produced by oil sand industry. To achieve this, the effects of NaCl, Na₂SO₄, and saline release water from composite tailings (CT) on hyphal growth of two AM fungal isolates from non-saline (Rhizophagus irregularis DAOM 181602, Rhizophagus sp. DAOM 227023) and three isolates of R. irregularis isolated from saline or sodic soils (DAOM 234181, DAOM241558, and DAOM241559) were tested in vitro. Pre-symbiotic hyphal growth of the five isolates, in absence of a host plant, decreased with increasing salt stress and no spores germinated in CT. The symbiotic extraradical phase of the four isolates of R. irregularis developed well in saline media compared to the Rhizophagus sp. Nevertheless, fungal development of the four R. irregularis isolates differed in saline media indicating phenotypic variations between isolates.     

Effects of Preconditioning Through Mycorrhizal Inoculation on the Control of Melon Root Rot and Vine Decline Caused by Monosporascus cannonballus

The use of inoculum of arbuscular mycorrhizal fungi (AMF) in nursery represents a promising field in horticulture because of its known benefits in terms of plant growth and bioprotection. The present work was undertaken to determine the effect of mycorrhizal inoculation with Rhizophagus irregularis in a nursery medium on the containment of melon root rot and vine decline (MRRVD) caused by the soil‐borne pathogen Monosporascus cannonballus. The percentage of mycorrhization, biomass and yield following mycorrhizal inoculation were also evaluated. Biocontrol activity was assessed in greenhouse pot experiments upon artificial inoculation of M. cannonballus and in a two‐season field experiment under production conditions in an unheated greenhouse with a history of MRRVD. On the basis of the mycorrhization parameters, the interaction appeared to be established within 30 days after inoculation. The total shoot growth in the mycorrhized plants was significantly higher when compared to the control, while the root growth was unaffected. Upon artificial inoculation of M. cannonballus, mycorrhization provided complete protection against the pathogen. Greenhouse experiments under production conditions during spring cropping season showed that pretransplanting inoculation with R. irregularis significantly decreased the severity of the disease. Also, the average fruit weight of mycorrhized plants was significantly higher than the untreated control. Nevertheless, in summer crop, the bioprotection activity of AMF failed. Present results indicate that the use of AMF in a nursery setting can contribute to the prevention of the onset of this problematic soil‐borne disease within a sustainable and integrated soil‐borne disease management.     

Catecholamine und 5-Hydroxytryptamin im Nervensystem von Seesternen und Enteropneusten

Zusammenfassung In den einfachen epithelialen Nervensystemen des Seesterns Astropecten irregularis und der Enteropneusten Harrimania kupfferi und Ptychodera flava sind Noradrenalin und 5-Hydroxytryptamin fluoreszenzmikroskopisch und mikrospektrofluorimetrisch nachgewiesen worden. Noradrenalin ist bei Astropecten weitgehend auf eine basale Faserschicht des ektoneuralen Systems beschränkt, während 5-HT vor allem apikal verbreitet ist. Fluoreszierende Perikaryen und synapsenartige Verdickungen sind selten und wurden vor allem bei den Enteropneusten gefunden. Vermutlich ist Noradrenalin in erster Linie im sensiblen Anteil der untersuchten Nervensysteme lokalisiert.

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Catecholamines and 5-hydroxytryptamine in the starfish and enteropneust nervous systems

Summary Noradrenaline and 5-hydroxytryptamine have been demonstrated with the fluorescence microscope and a microspectrofluorimeter in the primitive epithelial nervous systems of the starfish Astropecten irregularis and the Enteropneusts Harrimania kupfferi and Ptychodera flava. In Astropecten noradrenaline is largely confined to a basal fibre layer in the ectoneural system, 5-HT occurs predominantly in an apical localization. Pericarya and synaptic thickenings emitting a characteristic fluorescence are rare and have been found mainly in the Enteropneust species. Presumably, noradrenaline is predominantly localized in the sensory part of nervous systems investigated.

Herrn Prof. A. G. E. Pearse, Dept. of Histochemistry, und besonders Herrn Dr. F. W. D. Rost, Unit of Microspectrofluorimetry, Royal Postgraduate Medical School, London, danke ich für die Hilfe bei der Benutzung ihrer mikrospektrofluorimetrischen Anlage und des Computers beim Auswerten der Daten.