The localization of a resource is a critical step in an animal’s life. The survival of an individual and its reproductive success rely on the successful localization of proper food sources, mates, or favourable sites for rearing the progeny. Sensory systems must optimize the processing of input to permit timely and efficient extraction of information. Thus, the olfactory system meets the challenges to identify those components that belong to a target odour as distinct from those that are present in the background. The interactions between pheromones and plant volatiles in moths constitute a unique model system to investigate the very general question of the extraction of the specific signal in a noisy environment. Sex pheromones mediate specific mate location and are the crucial cues for reproduction in moths. Plants are a tremendous source of volatile compounds that constitute, quantitatively and qualitatively, a major set of sensory cues for insects. Pheromonal and non-pheromonal odorant compounds are detected by specific olfactory receptor neurons (ORNs) and are differentially processed in the antennal lobes (ALs) of males. However, the addition of plant odour modulates the orientation behaviour to sex pheromone and interactions between both stimuli take place at peripheral as well as central levels of the olfactory system. Our project aims to understand how pest insects, such as the black cutworm moth Agrotis ipsilon, meet the challenge to extract information through their olfactory system on mate identity and localisation, not only from the specific pheromone signal, but possibly also from plant odour cues, in a highly changing odorant background. Our program will be structured so as to investigate the interactions between the specific signal and the odorant background at the three levels of integration of the odour information: its detection (ORNs), its processing in the brain (olfactory sensory areas of the ALs) and the integrated motor response (male behaviour). Orientation to pheromone according to the odorant context will be investigated trough trajectometry to determine i) to which extent the male response to female pheromone depends on the plant context; ii) how the spatiotemporal pattern of plant-pheromone information impacts the insect's movement toward the pheromone source and iii) whether the insect is acquiring cues from its immediate olfactory environment for locating a sex partner. The effects of plant compounds on the intensity and quality coding of the pheromone by ORNs will be analysed by electrophysiological and biochemical approaches. A combination of a powerful technique to measure global activity in the ALs (Ca-imaging) with the high resolution of electrophysiology (single neuron recording) will be used to investigate neural representations of pheromone-plant mixtures in the moth ALs. Through this integrated vision, we expect to gain a better understanding of the neural and behavioural processes that allow an animal to maintain a high level of specificity and sensitivity of its communication in a chemical noise and to understand how it can use the context in addition to a specific signal in its search for a localized resource. Both achievements have practical issues in the case of pheromones by offering the basic knowledge for a better predictability of the response to synthetic attractants used for the monitoring of insect populations and by contributing to the design of improved attractants for their control. Finally, we believe that a better understanding of the effects of volatile organic compounds (VOCs) on reproduction of arthropod species is also relevant to environmental science because of the expected modifications in biogenic VOCs emission due to global climatic change and human activities.

Project aims: Oil from seeds constitutes a key component of both human and livestock diets, which consumption is steeply increasing worldwide. Then, fatty acids composing triacylglycerols (TAGs) accumulated in plant seeds are structurally similar to long chain hydrocarbons and consequently represent logical and competitive alternatives to hydrocarbon-based products for the production of detergents, paints, plastics and lubricants (green chemistry). The increasing demand of plant oils for such industrial and nutritional applications highlights the urgent need to develop new methodologies to increase seed oil content when only little progress has been made by conventional breeding over the last decade. The successful engineering of domesticated high yielding oil crop species now requires a full elucidation of the mechanisms controlling the production of fatty acids and their assembly into TAGs. The TAG biosynthetic network comprises two blocks of reactions: block A is composed of plastidial enzymes involved in fatty acid synthesis, while block B of reactions is composed of acylating enzymes involved in TAG assembly in the ER. So far, most biotechnological approaches aimed at increasing seed oil content have put the focus on block B, thought to contain the few metabolic bottlenecks limiting seed oil production. However, metabolic control analysis experiments have recently shown that control of flux is exerted both by block A and block B. Within each of these blocks, metabolic control is then further shared between several enzymatic steps. Thus, it is essential to elucidate the regulation of block A to find out new biotechnological tools able to efficiently stimulate fatty acid synthesis. Recent data indicate that block A is highly regulated at the transcriptional level and that a coordinated activation of most genes encoding enzymes of block A is necessary to stimulate the rate of fatty acid production. This is the reason why this project is focused on the transcriptional regulation of block A. Work plan: This project aims to elucidate the transcriptional regulation of fatty acid biosynthesis in the model plant Arabidopsis and to provide us with new ways to modify seed filling in the support of sustainable agriculture. Our project has three major objectives: - The first is to isolate an original set of transcription factors involved in the control of fatty acid synthesis in Arabidopsis. - The second is to provide a deep understanding of the regulatory complex controlling the transcription of lipogenic genes. - The third is to exploit this knowledge to boost fatty acid production in seeds in the frame of a biotechnological approach. Expected results: - The main outcome of the project will consist in original knowledge about the regulation of fatty acid biosynthesis in plants. - The expected results of the project are mainly fundamental, even though biotechnological tools will be developed in the model species Arabidopsis as a proof of concept. Tools and strategies tested in this project may then be applied to the improvement of oil yields on oilcrops such as Brassica napus and the generation of new varieties of bioeconomic interest.

Epigenetic is defined as the study of heritable modifications in gene expression without changes in DNA sequence. Behind this very straightforward definition, the complex mechanisms underlying epigenetic modifications and chromatin dynamic are now very widely studied, in particular in plant models such as Arabidopsis. Recent high-throughput analyses revealed the epigenetic landscapes of Arabidopsis like variations in DNA methylation, histone modifications and small RNAs abundance, as well as epigenetic polymorphisms in transcribed regions of different accessions. Studies of plant natural variation have been focused mainly on sequence variation, and little is known about the role of epigenetic machinery in these processes. We now clearly need to isolate and study more epialleles to understand the significance of inherited epigenetic alterations in natural populations. In the Institut Jean Pierre Bourgin, several groups are interested in the analysis of Arabidopsis natural variation as a source of biodiversity. Many different quantitative trait loci (QTL) responsible for these variations were determined and the genes underlying these QTLs revealed. Interestingly, genes for which the polymorphism observed at the nucleotide level in the parental accessions cannot explain the phenotype of certain recombinant inbred lines (RILs), were also identified. The objective of this project is to characterize natural epivariants with phenotypic consequences and investigate the mechanisms underlying them. The first part of the project will focus on a new epiQTL, SG1. We believe that the SG1 protein is involved directly or indirectly in the epigenetic control of certain loci, including itself. Preliminary results have shown that SG1 is more methylated in certain accessions. The analyse of the profiles of DNA methylation and histone modifications will be further determined. We will identify the partners of the SG1 protein, its cellular localisation and targets. Finally, we will characterise the epimutants generated in a sg1 context since sg1 T-DNA mutants isolated in Col present stochastic phenotypes appearing after several generations and being reminiscent of epimutations. The second part of the project will focus on an incompatibility resulting from the Sha x Col cross. Preliminary analysis revealed a polymorphism of methylation between the two accessions at a locus on chromosome 5 (AtFOLT1 gene; transporter of folate). This could be explained by the presence of a second locus at chromosome 4 (AtFOLT2) suspected to be the origin of the methylation at chromosome 5 in Sha. First, we will reveal, the specific molecular structures (like tandem repeats) existing at incompatible loci in different accessions. The epigenetic marks of these regions will be determined. We will test whether incompatible loci are sufficient to trigger de novo DNA methylation and we will determine the molecular pathways that control these epigenetic variations. Since the first submission of this proposal in 2010, we have detected small RNAs targeting AtFOLT1 that will be further characterized in other accessions. Finally, since recent data point toward the fact that natural genetic variations modulate the biogenesis of small RNAs in Arabidopsis. We identified expression QTLs (eQTL) corresponding to genes involved in the biogenesis of small RNAs in two mapping populations. This exciting project will be further developed. We are in a very favorable position to characterize these new natural epivariants with the combination of our expertise on Arabidopsis epigenetics and the unique discovery of natural epivariants. This project is opening the way to a new challenging topic emerging in the natural variation field that will undoubtedly lead to the discovery of more examples of epigenetic mechanisms imparting information that regulates gene expression across generations.