Pyrosequencing analysis of the protist communities in a High Arctic meromictic lake: DNA preservation and change

High Arctic meromictic lakes are extreme environments characterized by cold temperatures, low nutrient inputs from their polar desert catchments and prolonged periods of low irradiance and darkness. These lakes are permanently stratified with an oxygenated freshwater layer (mixolimnion) overlying a saline, anoxic water column (monimolimnion). The physical and chemical properties of the deepest known lake of this type in the circumpolar Arctic, Lake A, on the far northern coast of Ellesmere Island, Canada, have been studied over the last 15 years, but little is known about the lake’s biological communities. We applied high-throughput sequencing of the V4 region of the 18S ribosomal RNA gene to investigate the protist communities down the water column at three sampling times: under the ice at the end of winter in 2008, during an unusual period of warming and ice-out the same year, and again under the ice in mid-summer 2009. Sequences of many protist taxa occurred throughout the water column at all sampling times, including in the deep anoxic layer where growth is highly unlikely. Furthermore, there were sequences for taxonomic groups including diatoms and marine taxa, which have never been observed in Lake A by microscopic analysis. However, the sequences of other taxa such as ciliates, chrysophytes, Cercozoa, and Telonema varied with depth, between years and during the transition to ice-free conditions. These seasonally active taxa in the surface waters of the lake are thus sensitive to depth and change with time. DNA from these taxa is superimposed upon background DNA from multiple internal and external sources that is preserved in the deep, cold, largely anoxic water column.

Identification of novel QTL for resistance to Fusarium head blight in a tetraploid wheat population

Most tetraploid durum wheat (Triticum turgidum L var. durum) cultivars are susceptible to Fusarium head blight (FHB). This study reports novel quantitative trait loci (QTL) associated with FHB resistance. A backcross recombinant inbred line (BCRIL) population was developed from the cross BGRC3487/2*DT735, and 160 lines were evaluated for resistance to Fusarium graminearum Schwabe (teleomorph Gibberella zeae (Schwein. Petch) in field trials over 3 years (2008-2010) and to a F. graminearum 3-acetyl-deoxynivalenol (3-ADON) chemotype in greenhouse trials. The population was genotyped with 948 polymorphic loci using DArT and microsatellite markers. Eleven QTL were associated with FHB resistance under field conditions on chromosomes 2A, 3B, 5A, 5B, 7A, and 7B. Two of these, QFhb.usw-3B from BGRC3487 and QFhb.usw-7A2, were consistently detected over environments. The QFhb.usw-3B QTL was in a similar position to a resistance QTL in hexaploid wheat. The combination of the two QTL reduced field index by 53.5%-86.2%. Two QTL for resistance to the 3-ADON chemotype were detected on chromosomes 1B and 4B. Both BGRC3487 and DT735 could provide new sources of FHB resistance and the combination of QTL reported here could be valuable tools in breeding FHB-resistant durum wheat.

Sex pheromone specificity: taxonomic and evolutionary aspects in lepidoptera

Sex pheromone specificity is the only obvious reproduction isolating mechanism for two tortricid species and two gelechiid species. Pheromones of the gelechiid species are cis-9-tetradecenyl acetate and trans-9-tetradecenyl acetate. Male response of one gelechiid species is inhibited by the pheromone of the other species. This could be important for sympatric evolutionary saltation.

La santé des racines : le monde de la complexité

L’étude des racines a été entreprise dans le laboratoire du Centre de recherche et de développement sur les sols et les grandes cultures pour tenter d’élucider l’effet inattendu d’un virus qui, exploité dans le contexte de la sélection végétale, aidait à augmenter le potentiel de biomasse de l’espèce. La complexité de la vie des racines amène bien des embûches dans de telles études. Le monde des interactions au niveau des racines est si complexe que la méthode cartésienne n’offre pas les outils adéquats pour comprendre le système. Malgré tout, on peut développer des méthodes utiles et efficaces pour comprendre et gérer cette complexité. Après avoir approfondi les acquis des méthodes cartésiennes, il faut aller vers des approches synthétiques offrant une possibilité de continuité des progrès académiques et pratiques. Les racines les mieux adaptées et les plus plastiques par rapport à leur écosystème possèdent de nombreuses propriétés probablement interreliées. Un progrès global vers la santé des racines est donc un but envisageable, et dont le succès serait important au niveau environnemental. La génétique et la régie peuvent y contribuer. Pour progresser dans ce domaine, il faut donc oser sortir des voies conventionnelles. Ce n’est pas seulement la difficulté d’une question complexe qui est en cause, mais également le fait que notre éducation nous a enseigné à éviter de côtoyer la complexité. L’approche réductrice ne permet de comprendre ni la santé des racines, ni celle de la plante, ni le lien entre la plante, ses ennemis, la rhizosphère, et l’environnement. C’est donc à juste titre que des philosophes nous mettent en garde contre les impacts du morcellement des connaissances. Ce texte s’inscrit dans le désir d’aborder le monde des racines dans sa complexité et d’éviter les pièges associés à la logique cartésienne à l’état pur.

Use of hen lysozyme for protection against bacterial contamination ofin vitro embryo cultures

Curative treatments with antibiotics and hen egg white lysozyme (HEWL) were used to salvage embryo cultures contaminated withBaccillus subtilis. The use of HEWL gave good control ofBaccillus subtilis, but no control ofErwinia. HEWL was better than antibiotics, being much less phytotoxic. The antibiotics piperacillin, ampicillin and imipenem were also found to be ineffective againstErwinia. HEWL, at a final concentration of 1 mg per mL, was used as a preventive and curative agent for routine use in embryo culture ofTriticum aestivum and other Triticeae, as it cured from 30% to 50% of bacterial contamination problems over a one year period. Standardin vitro culture precautions remained essential, as certain bacteria were not controlled by HEWL.

Production, morphology, and cytogenetics of Triticum aestivum (L.) Thell × Elymus scabrus (R. Br.) Love intergeneric hybrids obtained by in ovulo embryo culture

Intergeneric hybrids were produced between common wheat, Triticum aestivum (2n=6x=42, AABBDD), and an apomictic Triticeae species, Elymus scabrus (syn. Agropyron scabrum) (2n=6x=42, HHSSSS), the first successful report of this cross. Nine tiny, underdeveloped, and structureless embryos were obtained in vitro only by in ovulo embryo culture at 4 days after pollination, which gave rise to five mature hybrid plants. All the hybrid plants were vigorous and possessed a phenotype intermediate to the two parents. There were 2n=6x=42 (ABDHSS) somatic chromosomes in the hybrids. There was little or no homology between the parental genomes, as shown by an overall meiotic chromosome association of 32.83 I + 4.08 rod II + 0.21 ring II + 0.18 III + 0.02 IV. The hybrids were completely sterile and so far backcrosses to wheat parent have not been successful. Alternate approaches to induce gene transfer(s) from E. scabrus to wheat are being attempted.

Somatic embryogenesis and plant regeneration in Triticum aestivum x Leymus angustus F1 hybrids and the parental lines

Somatic embryos and plants were produced from cultured inflorescence and leaf segments of Triticum aestivum X Leymus anaustus F1 hybrids and the parental lines. Inflorescences showed a better capacity for somatic embryogenesis and plant regeneration than leaves. Leymus anaustus produced the highest number of embryogenic calli, while the hybrids were intermediate between this species and Triticum aestivum. Presence of 2,4-D was shown to be essential for induction and maintenance of somatic embryogenesis. Addition of five amino acids (glutamine, proline, asparagine, aspartic acid and glutamic acid) did not have any marked effect when they were used in the callus induction medium. The regenerated plants had the same morphology as the original plants. No cytological modification was observed in the examined plants.

A novel intergeneric hybrid in the Triticeae: Triticum aestivum x Psathyrost achys juncea

Two hybrid embryos of intergeneric origin between Triticum aestivum cv Fukuho (2n=6x=42, AABBDD) and Psathyrostachys juncea (2n=2x=14, NN) were successfully rescued. One hybrid plant had the expected chromosome number of 28 (ABDN), whereas the second plant had 35 chromosomes. The average meiotic chromosome pairing in the 35-chromosome hybrid was 21.87 univalents + 6.38 bivalents + 0.11 trivalents + 0.009 quadrivalents, which indicates that two copies of the N genome were present. Chromosome pairing in the 28-chromosome hybrid was low (1.35 bivalents), and pointed out the lack of homology between the wheat genomes and the P. juncea genome. These new hybrids showed some necrosis and chlorosis, which caused severe floral abortion in the plant that had 35 chromosomes. These problems became gradually less severe after 18 months.

Production and cytogenetics of hybrids of Triticum aestivum x Leymus innovatus

Hybrid plants were obtained between Triticum aestivum (2n=6x=42, AABBDD) and Leymus innovatus (2n=4x=28, JJNN) at a frequency varying from 0.4% to 1.2% of the pollinated florets. Improvement of the embryo culture medium resulted in a higher frequency of embryo rescue. Eight of ten hybrids had the expected chromosome number of 35 (ABDJN). Meiotic analysis indicated that there was no homology between the genomes of the two species. Two hybrids had only 28 chromosomes. Comparison of chromosome pairing between the two types of hybrids suggested that Leymus innovatus carries genes that affect chromosome pairing and behavior. The relatively high occurrence of spontaneous doubling in the meiocytes of these hybrids may indicate that backcrossing of the hybrids to wheat should be possible, although frequent chromosome irregularities observed in the meiocytes of the hybrids may decrease the probability of success of this step, which is essential to the process of gene transfer from L. innovatus to wheat.

Intergeneric hybrids of Triticum aestivum × Leymus multicaulis

Hybrids were obtained at a frequency of 0.53% of the pollinated florets by pollination of Triticum aestivum (2n = 6x = 42, AABBDD) cv. Norin 29 with Leymus multicaulis (2n = 4x = 28, JJNN). The hybrid plants were taller than both parents and the floral structure of the hybrid spike resembled a modified wheat spike. The hybrids had the expected somatic chromosome number of 35 (ABDJN). The average bivalent frequency per cell at metaphase I in the meiocytes was very low, 0.59 and 0.45, respectively, for the two hybrids studied, suggesting the absence of homology between the parental genomes. The meiotic abnormalities observed consisted of lagging chromosomes and cytokinesis irregularities, leading to the production of polyads containing micronuclei at the quartet stage. The backcrossing of one hybrid to wheat cv. Fukuho resulted in the production of one plant with 56 chromosomes. Preliminary results on the evaluation of the BC3 and BC2F2 derivatives for barley yellow dwarf virus resistance (BYDV) suggested that the transfer of BYDV resistance genes from L. multicaulis to wheat is possible.Key words: intergeneric hybrids, Leymus, wheat, rye-grass, wild rye, embryo rescue.

[Diagnosis of genital Chlamydia trachomatis infections using antigen detection and cell culture]

The purpose of this study is: 1. comparing the immuno-enzymatic method (E.L.I.S.A. Abbott) and the cellular culture in the screening of the chlamydial genital infections; 2. evaluating these two tests in post-treatment control. During a 3 month period, 825 patients of our S.T.D. Clinic are considered a risk group and 144 have a positive culture. The E.L.I.S.A. method presents a sensitivity of 70.8% and a specificity of 98.5%. On the other hand, the sensitivity rises up to 80.9% if we retain only the primary culture. Interesting fact: if the reading on the spectrophotometer (E.L.I.S.A. Quantum) is greater than 0.7, the culture is always positive. Being a sexual contact of an infected person, having more than one partner or an history of a S.T.D. in the past, all these factors increase the risk of a chlamydial positivity, but in female only. We observe that 76.5% of patients suffering from gonorrhea have also a chlamydial infection proven by culture. Following a post-treatment control of one week, 5 cases remain positive, that is 3 by E.L.I.S.A. and 2 by culture, while three weeks later all cases are negative. The E.L.I.S.A. method has a good correlation with culture, is highly specific and the reading of optic density seems useful in predicting a positive culture. Risk factors are not the same in male and female. The post-treatment controls by both methods are not always similar if they are performed after one or three weeks.

Intergeneric hybrids between Hordeum jubatum (4x) and Triticum aestivum (6x)

Twelve embryos of interspecific hybrids between Hordeum jubatum (4x) and Triticum aestivum (6x) cv. Fukuho were produced out of 280 pollinated florets. Embryos were minute and globular and only one of them was successfully grown in vitro. Plant morphology of the hybrid was intermediate between the two parents and hybrid vigor was observed. Several traits of the hybrid were characteristic of the Hordeum parent such as brittle rachis, long awn, outerglume characteristics, and foliage waxiness being the most prominent. Average meiotic chromosome pairing in the hybrid was 28.6 univalents + 3.2 bivalents + 0.007 trivalents, which is not above what would be expected in a common wheat haploid.Key words: intergeneric hybrids, Critesion, Hordeum, Triticum, meiosis.

Meiosis in Triticum aestivum × Elytrigia repens hybrids

The average meiotic configuration in Triticum aestivum × Elytrigia repens hybrids was 31.951 + 4.97 II + 0.03 IV per cell. Chromosome synapsis was likely due to autosyndesis between chromosomes of the S genomes and not due to intergenomic homology.Key words: hybrids, intergeneric, Elytrigia repens, Triticum aestivum, chromosome synapsis.

Sex Attractant of the Codling Moth: Characterization with Electroantennogram Technique

trans-8, trans-10-Dodecadien-1-ol is a sex attractant of the codling moth, Laspeyresia pomonella. Antennal responses (electroantennograms) to a series of monounsaturated compounds were used in determining the location and configuration of the two double bonds. The synthetic compound is very attractive to male codling moths in the field.