Search results for "INTERACTION"

Immunity and the emergence of virulent pathogens.

2013

6 pages; International audience; The emergence/re-emergence of infectious diseases has been one of the major concerns for human and wildlife health. In spite of the medical and veterinary progresses as to prevent and cure infectious diseases, during the last decades we have witnessed the emergence/re-emergence of virulent pathogens that pose a threat to humans and wildlife. Many factors that might drive the emergence of these novel pathogens have been identified and several reviews have been published on this topic in the last years. Among the most cited and recognized drivers of pathogen emergence are climate change, habitat destruction, increased contact with reservoirs, etc. These factor…

Grazing decreases N partitioning among coexisting plant species

2017

Herbivores play a key role in shaping ecosystem structure and functions by influencing plant and microbial community composition and nutrient cycling. This study investigated the long‐term effects of herbivores on plant resource acquisition. We explored differences in the natural δ15N signatures in plant, microbial and soil N pools, and examined mycorrhizal colonization in two tundra sites that have been either lightly or heavily grazed by reindeer for more than 50 years. The study examined changes in nutrient acquisition in five common tundra plants with contrasting traits and mycorrhiza status; the mycorrhizal dwarf shrubs, Betula nana, Vaccinium myrtillus and Empetrum hermaphroditum; a m…

Abundance–variance and abundance–occupancy relationships in a marine host–parasite system: The importance of taxonomy and ecology of transmission

2011

Abundance-occupancy and abundance-variance relationships are two of the most general macroecological patterns capturing essential fundamentals of the structuring of species distributions and are widely documented for free-living animal and plant species populations at different spatial scales. However, empirical data for parasites have been gathered using appropriate sampling designs only recently. We performed analyses across species of the variation in infection parameters and patterns of aggregation of the most widespread parasites in the marine sparid fish Boops boops across seven localities of two marine biogeographical regions, the North East Atlantic and the Mediterranean. We used a …

Spatiotemporal Structure of Host‐Pathogen Interactions in a Metapopulation

2009

International audience; The ecological and evolutionary dynamics of species are influenced by spatiotemporal variation in population size. Unfortunately, we are usually limited in our ability to investigate the numerical dynamics of natural populations across large spatial scales and over long periods of time. Here we combine mechanistic and statistical approaches to reconstruct continuous-time infection dynamics of an obligate fungal pathogen on the basis of discrete-time occurrence data. The pathogen, Podosphaera plantaginis, infects its host plant, Plantago lanceolata, in a metapopulation setting where the presence of the pathogen has been recorded annually for 6 years in similar to 4,00…

2019

Trade-offs have been shown to play an important role in the divergence of mating strategies and sexual ornamentation, but their importance in explaining warning signal diversity has received less attention. In aposematic organisms, allocation costs of producing the conspicuous warning signal pigmentation under nutritional stress could potentially trade-off with life-history traits and maintain variation in warning coloration. We studied this with an aposematic herbivore Arctia plantaginis (Arctiidae), whose larvae and adults show extensive variation in aposematic coloration. In larvae, less melanic coloration (i.e. larger orange patterns) produces a more efficient warning signal against pre…

Mixotrophic phytoplankton dynamics in a shallow Mediterranean water body: how to make a virtue out of necessity

2018

Mixotrophy is a combination of photosynthesis and direct access to organic carbon sources, mainly through osmotrophy or phagotrophy. This strategy is adopted by several, phylogenetically distinct, phytoplankton groups and is commonly occurring in marine, brackish and freshwater ecosystems. Traditionally, it has been put in relation to both scarcity of inorganic nutrients and poor light conditions. However, we observed blooms of the mixotrophic, toxic haptophyte Prymnesium parvum in different periods of the year and under variable resources availability. The analysis of a 6.5-year data set of phytoplankton weekly records from a Sicilian shallow lake (Biviere di Gela, south-eastern Sicily) al…

Glutathione deficiency of the Arabidopsis mutant pad2-1 affects oxidative stress-related events, defense gene expression and hypersensitive response

2011

L'article original est publié par The American Society of Plant Biologists; International audience; The Arabidopsis (Arabidopsis thaliana) phytoalexin-deficient mutant pad2-1 displays enhanced susceptibility to a broad range of pathogens and herbivorous insects that correlates with deficiencies in the production of camalexin, indole glucosinolates, and salicylic acid (SA). The pad2-1 mutation is localized in the GLUTAMATE-CYSTEINE LIGASE (GCL) gene encoding the first enzyme of glutathione biosynthesis. While pad2-1 glutathione deficiency is not caused by a decrease in GCL transcripts, analysis of GCL protein level revealed that pad2-1 plants contained only 48% of the wild-type protein amoun…

Immune response affects ant trophallactic behaviour.

2008

5 pages; International audience; Sociality is associated with many benefits that have favoured its evolution in social insects. However, sociability also presents disadvantages like crowding of large numbers of individuals, which may favour the spread of infections within colonies. Adaptations allowing social insects to prevent and/or control pathogen infections range from behavioural responses to physiological ones including their immune systems. In a state of infection, social interactions with nestmates should be altered in a way which might prevent its spreading. We simulated a microbial infection in workers of the ant Camponotus fellah by the administration of peptidoglycan (PGN) and t…

Risk of predation makes foragers less choosy about their food.

2017

18 pages; International audience; Animals foraging in the wild have to balance speed of decision making and accuracy of assessment of a food item's quality. If resource quality is important for maximizing fitness, then the duration of decision making may be in conflict with other crucial and time consuming tasks, such as anti-predator behaviours or competition monitoring. Individuals facing the risk of predation and/or competition should adjust the duration of decision making and, as a consequence, their level of choosiness for resources. When exposed to predation, the forager could either maintain its level of choosiness for food items but accept a reduction in the amount of food items con…

Elicitins trap and transfer sterols from micelles, liposomes and plant plasma membranes

1999

Using elicitins, proteins secreted by some phytopathogenic Oomycetes (Phytophthora) known to be able to transfer sterols between phospholipid vesicles, the transfer of sterols between micelles, liposomes and biological membranes was studied. Firstly, a simple fluorometric method to screen the sterol-carrier capacity of proteins, avoiding the preparation of sterolcontaining phospholipidic vesicles, is proposed. The transfer of sterols between DHE micelles (donor) and stigmasterol or cholesterol micelles (acceptor) was directly measured, as the increase in DHE fluorescence signal. The results obtained with this rapid and easy method lead to the same conclusions as those previously reported, u…