Effect of Intraspecific Competition and Substrate Type on Terpene Emissions from Some Mediterranean Plant Species

International audienceCompetition is an important factor that has been extensively reported in the Mediterranean area. There is evidence that leaf terpene accumulation may vary between plants growing on calcareous and siliceous soils. In the present study, leaf terpene emissions from potted seedlings of Pinus halepensis, Cistus albidus, and Quercus coccifera, growing under natural environmental conditions on calcareous and siliceous substrates, were studied by using a bag enclosure method. In both substrates, seedlings were potted alone and in intraspecific competition, to examine the effect of substrate type and that of intraspecific competition on terpene emissions. The results showed that competition favored: (i) overall monoterpene and sesquiterpene emissions from Q. coccifera; (ii) overall monoterpene emissions from P. halepensis; (iii) overall sesquiterpene emissions from C. albidus. Substrate type affected terpene emissions to a limited extent and in a species-specific way. Whereas for Q. coccifera, the overall monoterpene emissions and that of Allo-aromadendrene were favored on siliceous substrate, no significant changes were found in emissions from P. halepensis. Only the release of AR-curcumene from C. albidus was higher on siliceous substrate. We also found high variability in terpene emission composition from the study species, particularly for P. halepensis and Q. coccifera. These two species released both monoterpenes and sesquiterpenes, instead of monoterpenes only, as shown in previous studies

Environmental control of terpene emissions from Cistus monspeliensis L. in natural Mediterranean shrublands

The large amount of volatile organic compound (VOC) emitted by vegetation modifies air quality contributing to both tropospheric ozone and secondary organic aerosol production. A better understanding of the factors controlling VOC emissions by vegetation is mandatory in order to improve emission estimates derived from tropospheric chemistry models. Although the Mediterranean shrublands are particularly abundant and rich in emitting species, their emission potential is poorly known. Focusing on a VOC-emitting shrub species widespread in the Mediterranean area (Cistus monspeliensis L.), we measured and analysed its emissions of terpenes taking into account the age of individuals, the season of sampling and the soil type. Sampling was done under natural environmental conditions. Species of the genus Cistus are frequently reported to be storing species, although we found only one stored monoterpene and three sesquiterpenes in very low amount. Major emitted compounds were a-pinene and b-myrcene. Total terpene emissions were not influenced by plant age but emission of some individual terpenes was positively correlated with age. A strong seasonal effect was evidenced. A larger amount of terpenes was emitted during spring and summer than during fall and winter. Summer emission rates were nearly 70 times higher than winter emission rates. Total and individual terpene emissions were influenced by soil type; emissions on siliceous substrate were ca. seven times higher than those on calcareous substrate. In conclusion, it appears clearly that environmental factors such as soil nature and season should be taken into account in order to achieve improved modelling of terpene emissions by shrub species

Production métabolique d’une algue rouge, une arme chimique pour la proliferation

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Impact of in Situ Simulated Climate Change on Communities and Non-Indigenous Species: Two Climates, Two Responses

International audienc

Diving into the chemistry of sponge exo-metabolomes: contribution of brominated specialized metabolites

International audienceSponges produce structurally diverse specialized metabolites known for their biological/pharmacological potentials. In particular, the Mediterranean sponges Aplysina cavernicola and Agelas oroides produce brominated alkaloids with antimicrobial/anti-biofilm properties. A few targeted studies, performed on Caribbean species from the same genus, reported that the most abundant brominated alkaloid (e.g. aerothionin, oroidin) were detected in the seawater surrounding the sponges. Hence, such exo-metabolites (EM) could be collected from the seawater without destroying the sponge biomass

Leaf specialized metabolome of Quercus pubescens exposed to amplified drought

National audienceThe intensification of summer drought expected with climate change in the Mediterranean region can induce metabolism modifications in plants to help them cope with such conditions. In the long term, these modification may impact diversity and global ecosystem functioning.-an in situ experimental site, equipped with a rainfall exclusion device, allowed reduction of natural rainfall by 30% over the tree canopy.-leaves of ND and AD plots were collected in spring, summer and fall during 3 years (2 nd , 3 rd and 4 th years of drought application).-a targeted approach was used to focus on phenolic metabolites.-an untargeted approach permitted to study a broader metabolome variation according to drought. Targeted and untargeted approaches permitted to demonstrate a time lag of the phenylpropanoid pathway over leaf phenology when trees were exposed to drought. Quercetins, catechins and myricetins, specific to summer leaves were down-regulated to favor the biosynthesis of kaempferols, specific to automnal leaves. Further studies would be necessary to understand how this time lag phenology may impact ecosystem functioning. Three of them might be linked to rhododendrin (with apiosyl rhododendrin and galloyl rhododendrin / waiting for co-injection of standard to be confirmed). Untargeted approach: The effect of drought on Quercus metabolome was weak (ns in 2013 ; p < 0.05 for 2014 and 2015) whereas metabolome is mainly driven by seasons (p < 0.001 for all years, two-ways permanova). Targeted approach: a drought effect was observed for both years (p < 0.05), while the metabolomic profiles were mainly influenced by phenology (p < 0.001, two-ways permanova)

Exometabolites from the Mediterranean sponge Agelas oroides: where is oroidin?

International audienceSponges are filter-feeding sessile marine animals that are keystone species of various benthic ecosystems. They are known to produce a plethora of structurally diverse metabolites. Some of them are part of their toolbox for defense and communication strategies. When released, these (exo)metabolites may contribute to distant species interactions (Hay 2009; Santonja et al. 2018). In the course of our studies on the chemicaldiversity of exometabolites from sponges, we wanted to know whether Agelas oroides (Schmidt, 1864), a rather dominant species of Mediterranean marine ecosystems, releases its characteristic bromo-pyrrole alkaloids. A series of captures and enrichment experiments were performed in aquaria and in situ (Mauduit et al. 2023). MS-based metabolomics revealed the paucity of bromo-pyrrole alkaloids as exometabolites. Oroidin was not detected in seawater despite being the most abundant compound in A. oroides extract (Fig. 1), and as opposed to published results with Agelas conifera (Richelle-Maurer et al. 2003).Such findings prompted us to explore the fate of oroidin from the sponge biomass to the seawater. Thepresentation will delve into these experimentations, and illustrate how examining organisms in theirecosystems can lead to new discoveries even for extensively studied species

Exploring the diversity of brominated alkaloids naturally released by the sponge Aplysina cavernicola

International audienceAplysina species are marine sponges known to produce spiro-isoxazoline bromotyrosine alkaloids (e.g. aerothionin). It has been reported that the Caribbean sponge A. fistularis releases aerothionin in seawater with/without intentional stress. Such released compounds, herein called exo-metabolites (EM), could possibly exert their biological effects as marine chemical cues

Does competition stress decrease allelopathic potential?

International audienceIn natural communities, plants compete in different ways, among them chemical interactions in the form of allelopathy. Whereas the effects of abiotic stresses (temperature, light, nutrients, etc.) on the production of allelochemicals are well known, only few studies deal with the impact of the stress induced by competition. When they do so, these studies are done under experimental conditions. The aim of this study is to evaluate the effect of intra-specific competition on the production of allelochemicals and biomass of Pinus halepensis Mill. in a natural forest using three levels of density. Phenolics and aliphatic acids were extracted from pine needles, analysed and quantified by GC-MS. Trunks, branches, needles and necromass were measured. We observed an increase in alle-lochemical content at low or medium level of competition and a decrease at high competition level. Moreover trees in competition allocate proportionally more biomass to the trunk and less to foliage and branches. This study provides evidence of substantial changes in allocation between the primary and the secondary metabolism

Litter leachates have stronger impact than leaf litter on Folsomia candida fitness

International audienceTree litter leachates have stronger influence than litter itself on Folsomia candida fitness Tree litter leachates have stronger effect on F. candida fitness than grass litter due to their content in secondary metabolites Soluble phenolic compounds released by litter leaching can drive F. candida fitness Litter compounds leaching appears to be an important process in abovegroundbelowground interactions *Highlights (for review