Herbivore associated elicitor-induced defences are highly specific among closely related Nicotiana species

BACKGROUND: Herbivore-induced defence responses are often specific - different herbivores induce different defence responses in plants - and their specificity is largely mediated by chemical cues (herbivore-associated elicitors: HAEs) in insect oral or oviposition secretions. However, the specificity and the mechanisms of HAE-induced defence have not been investigated in the context of the evolutionary relationships among plant species. Here we compare the responses of six closely related Nicotiana species to a synthetic elicitor, N-linolenoyl-glutamic acid (C18:3-Glu) and HAE of two insect herbivores (the Solanaceae specialist Manduca sexta and generalist Spodoptera littoralis). RESULTS: HAE-induced defences are highly specific among closely related Nicotiana species at three perspectives. 1) A single Nicotiana species can elicit distinct responses to different HAEs. N. pauciflora elicited increased levels of JA and trypsin proteinase inhibitors (TPI) in response to C18:3-Glu and the oral secretions of M. sexta (OS(Ms)) but not to oral secretions of S. littoralis (OS(Sl)). In contrast, N. miersii only responded to OS(Sl) but not to the other two HAEs. The specific responses to different HAEs in Nicotiana species are likely due to the perception by the plant of each specific component of the HAE. 2) One HAE can induce different defence responses among closely related Nicotiana species. OS(Ms) and C18:3-Glu induced JA and TPI accumulations in N. linearis, N. attenuata, N. acuminata and N. pauciflora, but not in N. miersii and N. obtusifolia. 3) The effect of HAE-induced defences differ for the Solanaceae specialist M. sexta and the generalist S. littoralis. Among the four tested Nicotiana species, while the growth rate of M. sexta was only reduced by the induced defences elicited by C18:3-Glu; the growth rate of S. littoralis can be reduced by the induced defences elicited by all three HAEs. This is likely due to differences in the susceptibility of the specialist M. sexta and generalist S. littoralis to induced defences of their host. CONCLUSIONS: Closely related Nicotiana species elicit highly specific defence responses to herbivore associated elicitors and provide an ideal framework for investigating the molecular mechanisms and evolutionary divergence of induced resistance in plants. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12870-014-0406-0) contains supplementary material, which is available to authorized users

Contrasting baseline expression of stress axis genes in rainbow trout selected for divergent stress responsiveness

The expression of eight candidate genes, with roles implicated in the stress response and associated behaviour, was quantified in the brains of lines of rainbow trout, Oncorhynchus mykiss Walbaum, that were selectively bred for divergent cortisol responses to stress. These lines represent a low responding (LR) and high responding (HR) line that are known to differ in their stress physiology and behavioural phenotype with LR always dominating HR. To understand whether there is differential gene expression in the brains of these lines fish were held individually and then sampled for brain gene expression of eight candidate genes (AANAT, calcineurin, CRF, urotensin I, glucocorticoid receptor II, mineralocorticoid receptor, melatonin receptor 1a, and melanocortin 2 receptor) to obtain a better understanding of the gene expression profile between HR and LR. Seven genes were expressed at a significantly higher level in the low-responding line compared to the high-responding line, and four genes, AANAT, CRF, UI and CaN, were positively correlated with baseline plasma cortisol concentrations. Only AANAT was not significantly differentially expressed between the two stress lines (due to high variation among individuals). Hence there is clear evidence of a tangible relationship between gene expression and stress physiology in these animals prior to stress

Anti-androgens act jointly in suppressing spiggin concentrations in androgen-primed female three-spined sticklebacks - Prediction of combined effects by concentration addition

This is the post-print version of the final paper published in Aquatic Toxicology. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2013 Elsevier B.V.Increasing attention is being directed at the role played by anti-androgenic chemicals in endocrine disruption of wildlife within the aquatic environment. The co-occurrence of multiple contaminants with anti-androgenic activity highlights a need for the predictive assessment of combined effects, but information about anti-androgen mixture effects on wildlife is lacking. This study evaluated the suitability of the androgenised female stickleback screen (AFSS), in which inhibition of androgen-induced spiggin production provides a quantitative assessment of anti-androgenic activity, for predicting the effect of a four component mixture of anti-androgens. The anti-androgenic activity of four known anti-androgens (vinclozolin, fenitrothion, flutamide, linuron) was evaluated from individual concentration-response data and used to design a mixture containing each chemical at equipotent concentrations. Across a 100-fold concentration range, a concentration addition approach was used to predict the response of fish to the mixture. Two studies were conducted independently at each of two laboratories. By using a novel method to adjust for differences between nominal and measured concentrations, good agreement was obtained between the actual outcome of the mixture exposure and the predicted outcome. This demonstrated for the first time that androgen receptor antagonists act in concert in an additive fashion in fish and that existing mixture methodology is effective in predicting the outcome, based on concentration-response data for individual chemicals. The sensitivity range of the AFSS assay lies within the range of anti-androgenicity reported in rivers across many locations internationally. The approach taken in our study lays the foundations for understanding how androgen receptor antagonists work together in fish and is essential in informing risk assessment methods for complex anti-androgenic mixtures in the aquatic environment.European Commission and Natural Environment Research Council

Plasticity of boldness in rainbow trout, Oncorhynchus mykiss: do hunger and predation influence risk-taking behaviour?

Boldness, a measure of an individual's propensity for taking risks, is an important determinant of fitness but is not necessarily a fixed trait. Dependent upon an individual's state, and given certain contexts or challenges, individuals may be able to alter their inclination to be bold or shy in response. Furthermore, the degree to which individuals can modulate their behaviour has been linked with physiological responses to stress. Here we attempted to determine whether bold and shy rainbow trout, Oncorhynchus mykiss, can exhibit behavioural plasticity in response to changes in state (nutritional availability) and context (predation threat). Individual trout were initially assessed for boldness using a standard novel object paradigm; subsequently, each day for one week fish experienced either predictable, unpredictable, or no simulated predator threat in combination with a high (2% body weight) or low (0.15%) food ration, before being reassessed for boldness. Bold trout were generally more plastic, altering levels of neophobia and activity relevant to the challenge, whereas shy trout were more fixed and remained shy. Increased predation risk generally resulted in an increase in the expression of three candidate genes linked to boldness, appetite regulation and physiological stress responses – ependymin, corticotrophin releasing factor and GABAA – but did not produce a significant increase in plasma cortisol. The results suggest a divergence in the ability of bold and shy trout to alter their behavioural profiles in response to internal and exogenous factors, and have important implications for our understanding of the maintenance of different behavioural phenotypes in natural populations

"...they should be offering it": a qualitative study to investigate young peoples' attitudes towards chlamydia screening in GP surgeries

<p>Abstract</p> <p>Background</p> <p>Despite the known health and healthcare costs of untreated chlamydia infection and the efforts of the National Chlamydia Screening Programme (NCSP) to control chlamydia through early detection and treatment of asymptomatic infection, the rates of screening are well below the 2010-2011 target rate of 35%. General Practitioner (GP) surgeries are a key venue within the NCSP however; previous studies indicate that GP surgery staff are concerned that they may offend their patients by offering a screen. This study aimed to identify the attitudes to, and preferences for, chlamydia screening in 15-24 year old men and women attending GP surgeries (the target group).</p> <p>Methods</p> <p>We undertook 36 interviews in six surgeries of differing screening rates. Our participants were 15-24 year olds attending a consultation with a staff member. Data were analysed thematically.</p> <p>Results</p> <p>GP surgeries are acceptable to young people as a venue for opportunistic chlamydia screening and furthermore they think it is the duty of GP surgery staff to offer it. They felt strongly that it is important for surgery staff to have a non-judgemental attitude and they did not want to be singled out as 'needing' a chlamydia screen. Furthermore, our sample reported a strong preference for being offered a screen by staff and providing the sample immediately at the surgery rather than taking home a testing kit. The positive attitude and subjective norms demonstrated by interviewees suggest that young peoples' behaviour would be to accept a screen if it was offered to them.</p> <p>Conclusion</p> <p>Young people attending GP surgeries have a positive attitude towards chlamydia screening and given the right environment are likely to take up the offer in this setting. The right environment involves normalising screening by offering a chlamydia screen to all 15-24 year olds at every interaction with staff, offering screening with a non-judgemental attitude and minimising barriers to screening such as embarrassment. The GP surgery is the ideal place to screen young people for chlamydia as it is not a threatening place for them and our study has shown that they think it is the normal place to go to discuss health matters.</p