Defense suppression benefits herbivores that have a monopoly on their feeding site but can backfire within natural communities

Background: Plants have inducible defenses to combat attacking organisms. Hence, some herbivores have adapted to suppress these defenses. Suppression of plant defenses has been shown to benefit herbivores by boosting their growth and reproductive performance. Results: We observed in field-grown tomatoes that spider mites (Tetranychus urticae) establish larger colonies on plants already infested with the tomato russet mite (Aculops lycopersici). Using laboratory assays, we observed that spider mites have a much higher reproductive performance on russet mite-infested plants, similar to their performance on the jasmonic acid (JA)-biosynthesis mutant def-1. Hence, we tested if russet mites suppress JA-responses thereby facilitating spider mites. We found that russet mites manipulate defenses: they induce those mediated by salicylic acid (SA) but suppress those mediated by JA which would otherwise hinder growth. This suppression of JA-defenses occurs downstream of JA-accumulation and is independent from its natural antagonist SA. In contrast, spider mites induced both JA- and SA-responses while plants infested with the two mite species together display strongly reduced JA-responses, yet a doubled SA-response. The spider mite-induced JA-response in the presence of russet mites was restored on transgenic tomatoes unable to accumulate SA (nahG), but russet mites alone still did not induce JA-responses on nahG plants. Thus, indirect facilitation of spider mites by russet mites depends on the antagonistic action of SA on JA while suppression of JA-defenses by russet mites does not. Furthermore, russet mite-induced SA-responses inhibited secondary infection by Pseudomonas syringae (Pst) while not affecting the mite itself. Finally, while facilitating spider mites, russet mites experience reduced population growth. Conclusion: Our results show that the benefits of suppressing plant defenses may diminish within communities with natural competitors. We show that suppression of defenses via the JA-SA antagonism can be a consequence, rather than the cause, of a primary suppression event and that its overall effect is determined by the presence of competing herbivores and the distinct palette of defenses these induce. Thus, whether or not host-defense manipulation improves a herbivore inverted question marks fitness depends on interactions with other herbivores via induced-host defenses, implicating bidirectional causation of community structure of herbivores sharing a plant

Computer-supported inquiry learning: effects of training and practice

Inquiry learning requires the ability to understand that theory and evidence have to be distinguished and co-ordinated. Moreover, learners have to be able to control two or more independent variables when formulating hypotheses, designing experiments and interpreting outcomes. Can sixth-grade (9–10 years) children be trained to acquire these inquiry learning skills? Or is the opportunity to practice in a computer-supported simulation environment a sufficient condition to foster inquiry learning skills? In this study, two groups of sixth grade children were compared: a training group, and a practice group. The training group received an off-line inquiry learning training in which we focused on fostering strategies for proper inferencing and designing experiments. The practice group conducted four inquiry learning tasks during two practice sessions. Learning outcomes and inquiry learning process measures were collected to study whether training and practice resulted in desired changes in learning behaviour. Both training and practice resulted in better performance during the test problems. Compared to the practice group, the training group showed some advantage in discovering an interaction effect. Practice and training effects appeared to be dependent on type of domain

Avoidance and suppression of plant defenses by herbivores and pathogens

Plants are nutritious and hence herbivores and phytopathogens have specialized to attack and consume them. In turn, plants have evolved adaptations to detect and withstand these attacks. Such adaptations we call ‘defenses’ and they can operate either directly between the plant and the plant consumer or indirectly i.e. when taking effect via other organisms such as predators and parasitoids of herbivores. Plant defenses put selection pressure on plant-consumers and, as a result, herbivores and pathogens have evolved counter-adaptations to avoid, resist, or manipulate plant defenses. Here we review how plant consumers have adapted to cope with plant defenses and we will put special emphasis on the phenomenon of suppression of plant defense

Pharmacogenetics of taste: turning bitter pills sweet?

Personalised Therapeutic

Ephedrine as add-on therapy for patients with myasthenia gravis: protocol for a series of randomised, placebo-controlled n-of-1 trials

Contains fulltext : 155188.pdf (publisher's version ) (Open Access)INTRODUCTION: Myasthenia gravis (MG), a rare neuromuscular disease, is often initially treated using acetylcholinesterase inhibitors. Patients who do not respond adequately depend on the use of corticosteroids or other immunosuppressive medication, but these may have serious side effects. Clinical observations suggest that ephedrine can diminish, postpone or even prevent the need for immunosuppressive therapy when added to acetylcholinesterase inhibitors or low-dose prednisone. In the Netherlands, ephedrine is not licensed for MG nor is reimbursement guaranteed. MG is a rare condition, and ephedrine might be indicated only in a subset of patients. Thus, randomised controlled trials comparing large groups are difficult to conduct. We, therefore, aim to aggregate data from a small series of n-of-1 trials (also known as single patient trials) to assess the effect of ephedrine as add-on treatment for MG. METHODS AND ANALYSIS: Single-centre, placebo-controlled, double-blind, randomised, multiple crossover n-of-1 studies in 4 adult patients with generalised MG who show inadequate improvement on pyridostigmine and/or immunosuppressive drugs. Each n-of-1 trial has 3 cycles of two 5-day intervention periods. TREATMENT: 25 mg ephedrine or placebo, twice daily. MAIN OUTCOME MEASURE: Quantitative Myasthenia Gravis (QMG) test. STATISTICAL ANALYSIS: fixed effects linear model for QMG for all patients combined. SECONDARY OUTCOME MEASURES: Clinical: effects on MG-Composite and MG-Activities of Daily Living (MG-ADL) scales; QMG at individual level; adverse events. Acceptability of trial design: number of patients eligible and enrolled; number of treatment cycles completed; patients' and caregivers' experiences. ETHICS AND DISSEMINATION: This study was approved by the Medical Ethics Committee of Leiden University Medical Center, No. P14.108. Results of the trial will be reported in a peer-reviewed publication. Regulatory stakeholders will comment on the suitability of the trial for market authorisation and reimbursement purposes. TRIAL REGISTRATION NUMBER: This study is registered under EudraCT number 2014-001355-23, protocol no. 40960, V.1.0, registration date 27 March 2014

Asymmetrical trunk movement during walking improved to normal range at 3 months after corrective posterior spinal fusion in adolescent idiopathic scoliosis

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