Host plant resistance in Brachiaria grasses to the spittlebug Zulia colombiana

Twelve forage grass accessions including 11 accessions of Brachiaria Griseb, were evaluated in a glasshouse for host plant resistance to nymphs and tolerance to feeding damage caused by adults of Zulia colombiana (Lallemand) (Homoptera: Cercopidae). Resistance to nymphs was evaluated with a technique that provided uniform environmental conditions and abundant feeding sites. B. brizantha Stapf (cv. Marandú) was the most resistant of the accessions tested based on nymphal mortality, duration of nymphal stadia, and weight of adult females. Andropogon gayanus Kunth, resistant to spittlebug attack in the field, was susceptible under the conditions of this study. While growth habit and rooting characteristics may contribute to field resistance, other resistance factors are present within the genus Brachiaria, particularly in the case of B. brizantha cv. Marandú. The number of insect-days causing severe damage in the most tolerant species (B. dictyoneura Stapf and B. humidicola Schweick) was approximately six times greater than that necessary to cause the same level of damage to the most susceptible species (B. ruziziensis Germain & Evrard and B. decumbens Stapf). No difference was found in regrowth capacity between infested and noninfested plants within accessions. There was a significant positive correlation between number of insect-days causing severe damage (tolerance) and regrowth of infested plants.

---

Résumé Brachiaria est une graminée fourragère prometteuse pour les sols tropicaux acides, saturés d'aluminium. Z. colombiana est un Cercopidae très répandu, limitant l'utilisation de Brachiaria en Amérique Latine. La résistance (antibiose et tolérance) à Z. colombiana, de Brachiaria d'origines diverses a été examinée. B. brizantha cv. Marandù s'est révélé le plus résistant d'après la forte mortalité larvaire, la prolongation du développement larvaire, et le poids réduit des femelles adultes de Z. colombiana. Andropogon gayanus, résistant dans la nature, s'est révélé sensible. Ces résultats suggèrent que cette résistance de A. gayanus dans la nature pourrait être due à la structure du végétal et à son mode de croissance. Dans le cas de B. brizantha cv. Marandù, des facteurs supplémentaires de résistance, mis en évidence à partir de différents modes de croissance, ont été éliminés, de façon à identifier les mécanismes de l'antibiose présents chez Brachiaria. Une grande gamme de résistance aux attaques alimentaires a été observée chez Brachiaria. Les plus résistants ont besoin de 6 fois plus de jours d'attaque par Z. colombiana pour provoquer les dégâts observés sur individus sensibles.

     

Increase in hepatic microsomal lipid peroxidation mediated by α-adrenergic system under cold stress and noradrenaline treatment

A membrane protein recognized by monoclonal antibody SQM1 was identified in human squamous carcinomas, including those originating in the head and neck (SqCHN), lung and cervix. Cell lines derived from SqCHN of previously untreated patients expressed high amounts of this protein. In contrast, many cell lines established from SqCHN of patients previously treated with chemotherapy and/or radiation showed diminished amounts of this SQM1 protein. The expression of SQM1 antigen was determined in several SgCHN cell lines made resistant by exposure to methotrexate (MTX) in vitro. The parent cell lines all exhibited strong binding to SQM1 antibody. The MTX-resistant sublines showed much lower membrane binding of SQM1. The lowest SQM1 reactivity was found in cell lines with high resistance to MTX and with diminished rate of MTX transport. Some highly MTX-resistant cell lines which had high levels of dihydrofolate reductase, but which retained a high rate of MTX transport, also retained high levels of SQM1 binding. Reduced SQM1 protein was also found in SgCHN cells which developed resistance to the alkylating drug cis-platinum (CDDP) and which showed reduced membrane transport of CDDP. Cell growth kinetics and non-specific antigenic shifts were not responsible for the differences in SQM1 binding between the parent cell lines and their drug-resistant sublines. The finding of a novel protein which is reduced in cells resistant to MTX and CDDP could contribute to our understanding of the basic mechanisms of drug resistance. By detecting SQM1 protein in clinical specimens, it may be possible to monitor the development of drug resistance in tumors.Abbreviations SqCHN Squamous Carcinoma of the Head and Neck - MTX Methotrexate - CDDP Cis-Platinum - DHFR Dihydrofolate Reductase     

Degradation of 2-chloroethanol by wild type and mutants of Pseudomonas putida US2

A strain of Pseudomonas putida was isolated that was able to degrade 2-chloroethanol. The degradation proceeded via 2-chloroacetaldehyde and chloroacetate to glycolate. In crude extracts the enzymes for this degradation pathway could be detected. All enzymes proved to be inducible. The dehalogenase that catalyzed the dehalogenation of chloroacetate to glycolate was further characterized. It consisted of a single polypeptide chain with a molecular mass of 28 kDa. After induction the dehalogenase was expressed at a high level. In a mutant resistant to high concentrations of 2-chloroethanol the dehalogenase was no longer expressed. The mechanism of resistance seemed to be due to the inability to convert chloroacetate and export of this compound out of the cell.Non-standard abbreviations CEO 2-chloroethanol - DCPIP 2,6-dichlorophenolindophenol - FPLC fast protein liquid chromatography - PAGE polyacrylamide gelelectrophoresis - PES phenazine ethosulfate - PMS phenazine methosulfate - PQQ pyrroloquinoline quinone     

Induction of vancomycin resistance in Enterococcus faecium by inhibition of transglycosylation

Vancomycin resistance has recently been recognized among clinical isolates of enterococci. Resistance is inducible, and associated with production of a novel 39 kDa membrane protein. The mechanism by which exposure to vancomycin, which does not penetrate the cell membrane, induces resistance is unknown. In the vancomycin resistant strain Enterococcus faecium 228, resistance was also inducible by moenomycin, suggesting that inhibition of the transglycosylation step in peptidoglycan synthesis may be required for induction of resistance. Cytoplasmic pools of peptidoglycan precursors were increased after exposure to vancomycin or moenomycin, representing a potential means for regulation of induction.     

心房钠尿因子对麻醉家兔局部血流的影响

在42只麻醉家兔,观察了静脉注射心房肽Ⅱ(AtriopeptinⅡ,APⅡ)对局部血流量以及动脉内注射 AP Ⅱ 对局部血管阻力的影响。结果如下:(1)静脉注射 APⅡ(30μg/kg)5min后,平均动脉压(MAP)降低11.0±1.5mmHg(n=8,M±SE,下同),与溶剂对照组相比有明显差异(P相似文献   

抗马拉硫磷淡色库蚊不同基因型的自然内禀增长率及其对抗性演化的影响

本文涉及淡色库蚊(Culex pipiens pallens)抗马拉硫磷纯合子(RR)、杂合子(RS)和敏感纯合子(SS)的自然内禀增长率及其对马拉硫磷抗性演化的影响。RR、RS和SS的内禀增长率分别为0.1118、0.1171和0.1339。RR和RS基因型在无杀虫剂时呈现出繁殖不利性,RR和RS的相对适合度分别是SS的0.65和0.68。 影响淡色库蚊对马拉硫磷进化的某些因子在计算机上进行了模拟。模拟的因子包括R等位基因的起始频率(P_o)、所用马拉硫磷的剂量和迁入率(m)。模拟结果表明(I)不用药时R等位基因衰减是由于RR和RS基因型的繁殖不利性;(2)在起始种群N_o=200,P_o=0.1,使用杀死全部SS和RS的剂量(8ppm)处理,使R等位基因为有效隐性,并且m≥0.15时可阻止马拉硫磷抗性的发生。     

Promoters active in mammalian cells (pSV40) and in plants (pNOS) permit expression in yeast of the Tn5 APH(3') II gene

Abstract Four plasmids were constructed by associating Escherichia coli and yeast selection markers and replication origins to a structural gene coding for aminoglycoside phosphotransferase (APH(3')) controlled by different flanking sequences. We used the two bacterial genes of Tn5 (APH(3')II) and Tn903 (APH(3')I) as such and the chimeric pSVneo (APH(3')II) and pNOSneo (APH(3')II) constructs, functional in mammalian and plant cells, respectively. Yeast clones resistant to G418 were obtained with all plasmids except with that bearing the bacterial APH(3')II gene. The three plasmids harbouring the functional APH genes, however, conferred different levels of G418 resistance to yeast.     

Interspecific hybrids between Brassica napus L. and B. oleracea L. developed by embryo culture

Summary Interspecific hybrids between Brassica napus and B. oleracea are difficult to produce, and previous attempts to transfer economic characters from one species to the other have largely been unsuccessful. In these studies, oilseed rape cv. Tower (2n38) (B. napus) was crossed with broccoli and kale (2n18) (B. oleracea), and hybrid plants were developed from embryos in culture by either organogenesis or somatic embryogenesis. In rape × broccoli, F₁ plants were regenerated from hybrid embryos and the plants produced viable selfed seeds. F₅ plants (2n38) homozygous for white flower colour were selected for high oil content (47%) and Line 15; a selection from these plants produced fertile hybrids with rape, broccoli and kale without embryo culture. In reciprocal crosses between oilseed rape cv. Tower and an aphid resistant diploid kale, 28 and 56 chromosome F₁ hybrid plants were regenerated from somatic embryos. The 56 chromosome plants were self-fertile and it was concluded from F₂ segregation ratios that a single dominant gene controls resistance to cabbage aphid in kale. The 28 chromosome F₁'s were self-sterile, but these and the 56 chromosome F₁'s could be backcrossed to rape and kale. A cross between the F₁ (2n56) and a forage rape resulted in the selection of a cabbage aphid (Brevicoryne brassicae L.) resistant line (Line 3). Both Line 15 and Line 3 can serve as bridges for gene interchange between B. campestris, B. napus and B. oleracea, which has not been possible hitherto. Hybridisations between rape and tetraploid kale produced F₁ plants with 37 chromosomes. One F₂ plant possessed coronal scales and the inheritance was shown to be controlled by a single recessive gene unlinked to petal colour.This paper is dedicated to Mr. T. P. Palmer, a colleague and close friend who retired from the DSIR as Assistant Director of the Crop Research Division in September 1984     

Reaction centers from three herbicide-resistant mutants of Rhodobacter sphaeroides 2.4.1: sequence analysis and preliminary characterization

Many herbicides that inhibit photosynthesis in plants also inhibit photosynthesis in bacteria. We have isolated three mutants of the photosynthetic bacterium Rhodobacter sphaeroides that were selected for increased resistance to the herbicide terbutryne. All three mutants also showed increased resistance to the known electron transfer inhibitor o-phenanthroline. The primary structures of the mutants were determined by recombinant DNA techniques. All mutations were located on the gene coding for the L-subunit resulting in these changes Ile²²⁹ Met, Ser²²³ Pro and Tyr²²² Gly. The mutations of Ser²²³ is analogous to the mutation of Ser²⁶⁴ in the D1 subunit of photosystem II in green plants, strengthening the functional analogy between D1 and the bacterial L-subunit. The changed amino acids of the mutant strains form part of the binding pocket for the secondary quinone, Q _b . This is consistent with the idea that the herbicides are competitive inhibitors for the Q _b binding site. The reaction centers of the mutants were characterized with respect to electron transfer rates, inhibition constants of terbutryne and o-phenanthroline, and binding constants of the quinone UQ₀ and the inhibitors. By correlating these results with the three-dimensional structure obtained from x-ray analysis by Allen et al. (1987a, 1987b), the likely positions of o-phenanthroline and terbutryne were deduced. These correspond to the positions deduced by Michel et al. (1986a) for Rhodopseudomonas viridis.Abbreviations ATP adenosine 5-triphosphate - Bchl bacteriochlorophyll - Bphe bacteriopheophytin - bp basepair - cyt c²⁺ reduced form of cytochrome c - DEAE diethylami-noethyl - EDTA ethylenediamine tetraacetic acid - Fe²⁺ non-heme iron atom - LDAO lauryl dimethylamine oxide - Pipes piperazine-N,N-bis-2-ethane-sulfonic acid - PSII photosystem II - RC reaction center - SDS sodium dodecylsulfate - Tris tris(hydroxy-methyl)aminomethane - UQ₀ 2,3-dimethoxy-5-methyl benzoquinone - UQ₁₀ ubiquinone 50     

In vitro expression of partial resistance toPhytophthora palmivora by shoot cultures of papaya

Shoot apices ofCarica papaya were multiplied in vitro on solidified nutrient media supplemented with -naphthyl-acetic acid and 6-benzylaminopurine. The micropropagated shoots were inoculated in vitro, through a stem wound, with a sporangial suspension (1.2×10⁴ sporangia ml^-1) ofPhytophthora palmivora. The symptoms exhibited by the shoots in vitro were similar to those described previously for infection of the whole plant in the field. The time taken for the host tissue to become brown and to wilt and the time to sporulation of the pathogen were all recorded for each shoot of four varieties of papaya challenged with each of ten isolates ofP. palmivora. Significant differences were observed between host-pathogen combinations for these variables and host-specificity was detected amongst the isolates ofP. palmivora. The time taken for the shoot to wilt was positively correlated with the time to sporulation of the isolated but both these variables were negatively correlated with the time to browning of the shoot. In vitro selection for disease resistance will be useful during breeding programmes involving papaya genotypes which are maintained through clonal propagation.