Herbivory by a Phloem-Feeding Insect Inhibits Floral Volatile Production

There is extensive knowledge on the effects of insect herbivory on volatile emission from vegetative tissue, but little is known about its impact on floral volatiles. We show that herbivory by phloem-feeding aphids inhibits floral volatile emission in white mustard Sinapis alba measured by gas chromatographic analysis of headspace volatiles. The effect of the Brassica specialist aphid Lipaphis erysimi was stronger than the generalist aphid Myzus persicae and feeding by chewing larvae of the moth Plutella xylostella caused no reduction in floral volatile emission. Field observations showed no effect of L. erysimi-mediated floral volatile emission on the total number of flower visits by pollinators. Olfactory bioassays suggested that although two aphid natural enemies could detect aphid inhibition of floral volatiles, their olfactory orientation to infested plants was not disrupted. This is the first demonstration that phloem-feeding herbivory can affect floral volatile emission, and that the outcome of interaction between herbivory and floral chemistry may differ depending on the herbivore's feeding mode and degree of specialisation. The findings provide new insights into interactions between insect herbivores and plant chemistry

A Stereocontrolled Synthesis of the Hydrophobic Moiety of Rhamnolipids

International audienceA new approach toward the synthesis of the hydrophobic moiety of rhamnolipid derivatives has been developed, involving two key cross-metatheses and an unusual Mitsunobu reaction. Small structural variations of the side chains should enable a better understanding of the role of the lipid moiety in immunostimulatory and plant defense eliciting properties

Recycling Mitsunobu coupling: a shortcut for troublesome esterifications

International audienceAn unusual recycling Mitsunobu reaction proved to be successful to couple two fragments in the courseof the synthesis of the hydrophobic moiety of rhamnolipid derivatives. Based on the obtained pivotalintermediate, a one pot ‘cross-metathesis/reduction’ approach gave access to structural variations of theside chains. Further study of these molecules will contribute to a better understanding of the role of thelipid moiety in immunostimulatory and plant defense eliciting properties

Response of ladybird <i>C. septempunctata</i> to different odour combinations in a two-way olfactometer.

<p>Figures represent mean number of observations in each olfactometer arm (± s.e.). UD: undamaged <i>S. alba</i>. Le: <i>L. erysimi</i> Mp: <i>M. persicae</i>. The different sections represent different comparisons carried out: A.) comparisons to test attraction to undamaged <i>S. alba</i>; B.) comparisons to test for attraction to <i>L. erysimi</i>-damaged plants; C.) comparisons between <i>L. erysimi</i> damage and <i>M. persicae</i> damage. * 0.05</p

Floral volatiles from <i>Sinapis alba</i> infested with different numbers of aphids.

<p>Total amount of volatiles (micrograms, mean ± 95% confidence interval) emitted from <i>Sinapis alba</i> flower heads of undamaged plants and plants subjected to damage by either 50 (AD50), 100 (AD100) or 200 (AD200) <i>Lipaphis erysimi</i> over a 72 h period. Left: total for each aphid density treatment averaged over all time periods. Right: total for each time period averaged over different aphid density treatments. Aphid density had a negative effect on volatile production by <i>S. alba</i> (ANOVA, F_1,17 = 7.88, P = 0.012) and there was no interaction between aphid density and time (ANOVA, F_2,44<0.01, P = 0.997).</p

Volatile compounds in the headspace of vegetative parts of <i>Sinapis alba</i>.

<p>Plants subjected to herbivory by the aphids <i>Lipaphis erysimi</i> or <i>Myzus persicae</i>. Volatiles collected 48–72 hours after the start of damage. Means (± standard error). Compounds are in order of elution on an HP-1 GC column.</p>1<p>Mean (± s.e.) from six replicates (see Methods). (-) indicates that the compound was not detected.</p>2<p>4,8,12-Trimethyl-1,3,7,11-tridecatetraene.</p

Floral volatiles from <i>Sinapis alba</i> infested with different herbivores.

<p>Figures represent total volatiles (micrograms, mean ± 95% confidence interval). Volatiles were collected in two periods: 24–72 h after the start of herbivory by aphids <i>Lipaphis erysimi</i>, <i>Myzus persicae</i> or larvae of the moth <i>Plutella xylostella</i> and 72–96 h after the start of herbivory. Aphids caused a significant reduction in floral volatile emission at 24–72 h (ANOVA, F_3,12 = 5.50, P = 0.013) and 72–96 h after infestation (ANOVA, F_3,12 = 5.07, P = 0.017).</p

Response of aphid parasitoid <i>D. rapae</i> to odours from <i>S. alba</i> in a two-way olfactometer.

<p>Figures represent mean time spent in each arm in seconds (± s.e.). UD: undamaged flowering <i>S. alba</i>. Le: <i>L. erysimi</i>. Mp: <i>M. persicae</i>. ** 0.01</p

Community-acquired pneumonia mortality: a potential link to antibiotic prescribing trends in general practice

Background: community prescribing of antibiotics has decreased substantially in the UK in recent years. We examine the association between pneumonia mortality and recent changes in community-based antibiotic prescribing for lower respiratory tract infections (LRTI).Methods: retrospective analysis of aggregated data for pneumonia mortality, influenza incidence, and antibiotic prescribing for LRTI in England and Wales during 12-week winter periods between 1993/94 and 1999/2000.Results: winter antibiotic prescribing for LRTI showed a 30.0% decline since 1995/96. Over the same period, there was a 50.6% increase in winter excess pneumonia mortality adjusted for influenza incidence. Negative binomial regression analysis showed that the incidence of influenza alone had a significant association with winter pneumonia mortality (P&lt;0.001). The analysis also showed the reduction in antibiotic prescribing had a small but significant association with mortality (P&lt;0.001), when simultaneously modelling for influenza incidence.Conclusions: our findings suggest an association between recent reductions in antibiotic prescribing for LRTI in general practice and an increase in pneumonia mortality in England and Wales. This retrospective study of aggregate data represents the first attempt to assess the effect of limiting antibiotic prescribing on patient outcomes, and highlights the need to identify which patients benefit from antibiotic treatment for LRTI.</p

Community-acquired pneumonia mortality: a potential link to antibiotic prescribing trends in general practice

Background: community prescribing of antibiotics has decreased substantially in the UK in recent years. We examine the association between pneumonia mortality and recent changes in community-based antibiotic prescribing for lower respiratory tract infections (LRTI).Methods: retrospective analysis of aggregated data for pneumonia mortality, influenza incidence, and antibiotic prescribing for LRTI in England and Wales during 12-week winter periods between 1993/94 and 1999/2000.Results: winter antibiotic prescribing for LRTI showed a 30.0% decline since 1995/96. Over the same period, there was a 50.6% increase in winter excess pneumonia mortality adjusted for influenza incidence. Negative binomial regression analysis showed that the incidence of influenza alone had a significant association with winter pneumonia mortality (P&lt;0.001). The analysis also showed the reduction in antibiotic prescribing had a small but significant association with mortality (P&lt;0.001), when simultaneously modelling for influenza incidence.Conclusions: our findings suggest an association between recent reductions in antibiotic prescribing for LRTI in general practice and an increase in pneumonia mortality in England and Wales. This retrospective study of aggregate data represents the first attempt to assess the effect of limiting antibiotic prescribing on patient outcomes, and highlights the need to identify which patients benefit from antibiotic treatment for LRTI.</p