Expression Of Different Mechanisms Research Articles

Expression of different mechanisms of resistance to insects in groundnut under field conditions

Host plant resistance is an important component of pest management, and information on contribution of different mechanisms of resistance is important for developing cultivars with resistance to the target pests. Therfore, we studied the contribution of different components of resistance in five groundnut genotypes to three insect species occurring in India under field conditions. Plant damage by the larvae of Helicoverpa armigera, Spodoptera litura, and leafhoppers (Empoasca kerri) was evaluated visually on a 1 – 9 damage rating (DR) scale (1 being 80 % leaf damage). Further, the activities of various plant defensive enzymes [peroxidase (POD), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), superoxide dismutase (SOD), ascorbate peroxidase (APX), lipoxygenase (LOX) and catalase (CAT)], and the amounts of total phenols, condensed tannins, hydrogen peroxide (H2O2), malondialdehyde (MDA) and proteins were also recorded. The genotypes ICGV 86699, ICGV 86031, ICG 2271 and ICG 1697 suffered lower leaf damage by H. armigera and S. litura (DR 2.6 – 3.2) and E. kerri (DR 2.0 - 3.2) as compared to JL 24 (DR 7.2 and 6.0, respectively). ICGV 86699, ICGV 86031, ICG 2271 and ICG 1697 exhibited greater enzymatic activity, and had more amounts of phenols, condensed tannins, hydrogen peroxide and proteins than the susceptible check, JL 24. There was a positive association between leaf damage and the activity of the defensive enzymes, and the amounts of phenols, condensed tannins and H2O2. These results suggested that the plant defensive enzymes such as POD, PPO, LOX, PAL, SOD, APX and CAT were involved in genotypic resistance to insects, and the resistant genotypes accumulated phenols, condensed tannins, and H2O2 to impart resistance to insects. This information will be useful for developing groundnut genotypes with resistance to insects for sustainable crop production.

Efflux pump inhibitors (EPIs) as new antimicrobial agents against Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic human pathogen and one of the leading causes of nosocomial infections worldwide. The difficulty in treatment of pseudomonas infections arises from being multidrug resistant (MDR) and exhibits resistance to most antimicrobial agents due to the expression of different mechanisms overcoming their effects. Of these resistance mechanisms, the active efflux pumps in Pseudomonas aeruginosa that belong to the resistance nodulation division (RND) plays a very important role in extruding the antibiotics outside the bacterial cells providing a protective means against their antibacterial activity. Beside its role against the antimicrobial agents, these pumps can extrude biocides, detergents, and other metabolic inhibitors. It is clear that efflux pumps can be targets for new antimicrobial agents. Peptidomimetic compounds such as phenylalanine arginyl β-naphthylamide (PAβN) have been introduced as efflux pump inhibitors (EPIs); their mechanism of action is through competitive inhibition with antibiotics on the efflux pump resulting in increased intracellular concentration of antibiotic, hence, restoring its antibacterial activity. The advantage of EPIs is the difficulty to develop bacterial resistance against them, but the disadvantage is their toxic property hindering their clinical application. The structure activity relationship of these compounds showed other derivatives from PAβN that are higher in their activity with higher solubility in biological fluids and decreased toxicity level. This raises further questions on how can we compact Pseudomonas infections. Of particular importance, the recent resurgence in the use of older antibiotics such as polymyxins and probably applying stricter control measures in order to prevent their spread in clinical sittings.

Influence of Cytoplasmic Male Sterility on Expression of Different Mechanisms of Resistance in Sorghum to <I>Atherigona soccata</I> (Diptera: Muscidae)

Atherigona soccata (Rondani) (Diptera: Muscidae) is one of the most important pests of sorghum, Sorghum bicolor (L.) Moench, in Asia, Africa, and the Mediterranean Europe. Exploitation of cytoplasmic male sterility (CMS) for hybrid production has resulted in considerable narrowing of the genetic base and may increase the vulnerability of this crop to insect pests. Therefore, we studied the expression of different mechanisms of resistance in sorghum to A. soccata in CMS (A) and maintainer (B) lines of 12 genotypes under field and greenhouse conditions. The CMS lines of A. soccata-resistant genotypes were preferred for oviposition (78.5 versus 71.5% plants with eggs) and suffered greater deadheart incidence (47.6 versus 41.6%) than the corresponding maintainer lines, whereas such differences were not apparent in CMS lines belonging to the susceptible genotypes (92.7 versus 92.3% plants with eggs and 75.6 versus 74.6% deadhearts) under multichoice field conditions. Similar differences also were observed under controlled conditions in the greenhouse. The larval period (9.0 versus 8.8 d) and pupal mortality (18.4 versus 13.4%) were greater on maintainer lines than that on the CMS lines in the resistant group. The male and female pupal weights, fecundity, and antibiosis index were greater on the CMS than on the maintainer lines. The maintainer lines showed better recovery resistance than the CMS lines, but no such differences were observed in tiller deadhearts. The differences in susceptibility to A. soccata were greater in the A. soccata resistant CMS and maintainer lines than in the CMS and maintainer lines belonging to susceptible genotypes. Conversion of A. soccata-resistant genotypes into alternate less susceptible cytoplasmic backgrounds may be undertaken for developing sorghum hybrids with stable resistance to A. soccata.

Influence of Cytoplasmic Male Sterility on Expression of Different Mechanisms of Resistance in Sorghum to Atherigona soccata (Diptera: Muscidae)

Influence of Cytoplasmic Male Sterility on Expression of Different Mechanisms of Resistance in Sorghum to Atherigona soccata (Diptera: Muscidae)

Psychiatric symptoms in neurologically asymptomatic Huntington's disease gene carriers: a comparison with gene negative at risk subjects

Psychiatric profiles of two at-risk groups [Huntington's disease (HD) gene carriers and non-carriers] were compared by means of a computerized battery and a structured interview. To avoid confounding, only subjects who were free from neurological and cognitive deficits (neurologically asymptomatic) were included in the study. To avoid evaluation biases, all subjects were seen before the genetic testing was undertaken. Gene carriers had significantly worse recognition memory and scored higher in measures of irritability than controls. The groups also differed in terms of the factor structure of their psychiatric symptoms. None of the subjects qualified for a psychiatric diagnosis at the time of assessment. The groups differed with respect to their profile of psychiatric symptoms. It is hypothesized that these differences are the expression of different mechanisms, i.e. that cognitive deficits relate more to genetic factors and neurotic complaints more to being brought up in a disturbed family background. Issues concerning instrument sensitivity, selection bias and the advantage of seriatim assessments are discussed.