Endosymbiosis drives transcriptomic adjustements and genomic adapatations in cnidarians

To decipher inter-partner signaling within the cnidarian-dinoflagellate endosymbiosis, we developed genomic resources (cDNA library and microarrays) for the symbiotic sea anemone Anemonia viridis. Differential gene expression was quantified during thermal stress, with and without UV radiation, between symbiotic vs aposymbiotic specimens and gastroderm vs epidermis tissues. During stress time-course experiments, each stress showed a specific gene expression profile with very little overlap. We show that the major response to thermal stress is rapid (24 hours) but returns to the baseline levels after 2 days. UVR alone has little effect but potentiates thermal stress, as expression of a second set of genes becomes differentially expressed at day 5. Analysis of genes differentially expressed between symbiotic vs bleached and symbiotic vs stressed specimens defined a restricted subset of genes (Kern). Tissue specific expression mapping of Kern genes showed that many were specifically enhanced in the symbiotic cells (gastroderm). Altogether, these data define the Kern genes as major molecular components of the symbiotic interaction. Functional annotations highlighted several pathways including collagen fibrillogenesis, vesicular trafficking, lipid metabolism, calcium signaling, inorganic carbon transfer and cell death, that were modified by stress. Phylogenomic investigations of several Kern genes (calumenin, NPC2, SYM32, dermatopontin, and Rhbg) demonstrate that these issued from cnidarian specific duplication events, with the Kern member being preferentially expressed in the gastroderm and specifically responding to stress. Such host specific genes subfunctionalizations suggest both genomic and transcriptomic adaptations driven by the physiological constraints of endosymbiosis

SPODOBASE : an EST database for the lepidopteran crop pest Spodoptera

BACKGROUND: The Lepidoptera Spodoptera frugiperda is a pest which causes widespread economic damage on a variety of crop plants. It is also well known through its famous Sf9 cell line which is used for numerous heterologous protein productions. Species of the Spodoptera genus are used as model for pesticide resistance and to study virus host interactions. A genomic approach is now a critical step for further new developments in biology and pathology of these insects, and the results of ESTs sequencing efforts need to be structured into databases providing an integrated set of tools and informations. DESCRIPTION: The ESTs from five independent cDNA libraries, prepared from three different S. frugiperda tissues (hemocytes, midgut and fat body) and from the Sf9 cell line, are deposited in the database. These tissues were chosen because of their importance in biological processes such as immune response, development and plant/insect interaction. So far, the SPODOBASE contains 29,325 ESTs, which are cleaned and clustered into non-redundant sets (2294 clusters and 6103 singletons). The SPODOBASE is constructed in such a way that other ESTs from S. frugiperda or other species may be added. User can retrieve information using text searches, pre-formatted queries, query assistant or blast searches. Annotation is provided against NCBI, UNIPROT or Bombyx mori ESTs databases, and with GO-Slim vocabulary. CONCLUSION: The SPODOBASE database provides integrated access to expressed sequence tags (EST) from the lepidopteran insect Spodoptera frugiperda. It is a publicly available structured database with insect pest sequences which will allow identification of a number of genes and comprehensive cloning of gene families of interest for scientific community. SPODOBASE is available from URL

Symbiont Chloroplasts Remain Active During Bleaching-Like Response Induced by Thermal Stress in Collozoum pelagicum (Collodaria, Retaria)

Collodaria (Retaria) are important contributors to planktonic communities and biogeochemical processes (e.g., the biologic pump) in oligotrophic oceans. Similarly to corals, Collodaria live in symbiosis with dinoflagellate algae, a relationship that is thought to explain partly their ecological success. In the context of global change, the robustness of the symbiotic interaction, and potential subsequent bleaching events are of primary interest for oceanic ecosystems functioning. In the present study, we compared the ultrastructure, morphology, symbiont density, photosynthetic capacities and respiration rates of colonial Collodaria exposed to a range of temperatures corresponding to natural conditions (21°C), moderate (25°C), and high (28°C) thermal stress. We showed that symbiont density immediately decreased when temperature rose to 25°C, while the overall Collodaria holobiont metabolic activity increased. When temperature reached 28°C, the holobiont respiration nearly stopped and the host morphological structure was largely damaged, as if the host tolerance threshold has been crossed. Over the course of the experiment, the photosynthetic capacities of remaining algal symbionts were stable, chloroplasts being the last degraded organelles in the microalgae. These results contribute to a better characterization and understanding of temperature-induced bleaching processes in planktonic photosymbioses

Adaptations to Endosymbiosis in a Cnidarian-Dinoflagellate Association: Differential Gene Expression and Specific Gene Duplications

Trophic endosymbiosis between anthozoans and photosynthetic dinoflagellates forms the key foundation of reef ecosystems. Dysfunction and collapse of symbiosis lead to bleaching (symbiont expulsion), which is responsible for the severe worldwide decline of coral reefs. Molecular signals are central to the stability of this partnership and are therefore closely related to coral health. To decipher inter-partner signaling, we developed genomic resources (cDNA library and microarrays) from the symbiotic sea anemone Anemonia viridis. Here we describe differential expression between symbiotic (also called zooxanthellate anemones) or aposymbiotic (also called bleached) A. viridis specimens, using microarray hybridizations and qPCR experiments. We mapped, for the first time, transcript abundance separately in the epidermal cell layer and the gastrodermal cells that host photosynthetic symbionts. Transcriptomic profiles showed large inter-individual variability, indicating that aposymbiosis could be induced by different pathways. We defined a restricted subset of 39 common genes that are characteristic of the symbiotic or aposymbiotic states. We demonstrated that transcription of many genes belonging to this set is specifically enhanced in the symbiotic cells (gastroderm). A model is proposed where the aposymbiotic and therefore heterotrophic state triggers vesicular trafficking, whereas the symbiotic and therefore autotrophic state favors metabolic exchanges between host and symbiont. Several genetic pathways were investigated in more detail: i) a key vitamin K–dependant process involved in the dinoflagellate-cnidarian recognition; ii) two cnidarian tissue-specific carbonic anhydrases involved in the carbon transfer from the environment to the intracellular symbionts; iii) host collagen synthesis, mostly supported by the symbiotic tissue. Further, we identified specific gene duplications and showed that the cnidarian-specific isoform was also up-regulated both in the symbiotic state and in the gastroderm. Our results thus offer new insight into the inter-partner signaling required for the physiological mechanisms of the symbiosis that is crucial for coral health

Etude moléculaire des cytochromes P450 de la famille 4 chez le bar, Dicentrarchus labrax. Effets des xénobiotiques sur l'expression de ces gènes

*INRA UMR ROSE BP 2078 06606 Antibes cedex Diffusion du document : INRA UMR ROSE BP 2078 06606 Antibes cedex Diplôme : Dr. d'Universit

Endosymbiosis drives transcriptomic adjustements and genomic adapatations in cnidarians

To decipher inter-partner signaling within the cnidarian-dinoflagellate endosymbiosis, we developed genomic resources (cDNA library and microarrays) for the symbiotic sea anemone Anemonia viridis. Differential gene expression was quantified during thermal stress, with and without UV radiation, between symbiotic vs aposymbiotic specimens and gastroderm vs epidermis tissues. During stress time-course experiments, each stress showed a specific gene expression profile with very little overlap. We show that the major response to thermal stress is rapid (24 hours) but returns to the baseline levels after 2 days. UVR alone has little effect but potentiates thermal stress, as expression of a second set of genes becomes differentially expressed at day 5. Analysis of genes differentially expressed between symbiotic vs bleached and symbiotic vs stressed specimens defined a restricted subset of genes (Kern). Tissue specific expression mapping of Kern genes showed that many were specifically enhanced in the symbiotic cells (gastroderm). Altogether, these data define the Kern genes as major molecular components of the symbiotic interaction. Functional annotations highlighted several pathways including collagen fibrillogenesis, vesicular trafficking, lipid metabolism, calcium signaling, inorganic carbon transfer and cell death, that were modified by stress. Phylogenomic investigations of several Kern genes (calumenin, NPC2, SYM32, dermatopontin, and Rhbg) demonstrate that these issued from cnidarian specific duplication events, with the Kern member being preferentially expressed in the gastroderm and specifically responding to stress. Such host specific genes subfunctionalizations suggest both genomic and transcriptomic adaptations driven by the physiological constraints of endosymbiosis

Molecular cloning of a phthalate-inducible CYP4 gene (CYP4T2) in kidney from the sea bass Dicentrarchus labrax

International audienc

Catalase characterization and implication in bleaching of a symbiotic sea anemone

Symbiotic cnidarians are marine invertebrates harboring photosynthesizing microalgae (named zooxanthellae), which produce great amounts of oxygen and free radicals upon illumination. Studying antioxidative balance is then crucial to understanding how symbiotic cnidarians cope with ROS production. In particular, it is suspected that oxidative stress triggers cnidarian bleaching, i.e., the expulsion of zooxanthellae from the animal host, responsible for symbiotic cnidarian mass mortality worldwide. This study therefore investigates catalase antioxidant enzymes and their role in bleaching of the temperate symbiotic sea anemone Anemonia viridis. Using specific separation of animal tissues (ectoderm and endoderm) from the symbionts (zooxanthellae), spectrophotometric assays and native PAGE revealed both tissue-specific and activity pattern distribution of two catalase electrophoretypes, E1 and E2. E1, expressed in all three tissues, presents high sensitivity to the catalase inhibitor aminotriazole (ATZ) and elevated temperatures. The ectodermal E1 form is responsible for 67% of total catalase activity. The E2 form, expressed only within zooxanthellae and their host endodermal cells, displays low sensitivity to ATZ and relative thermostability. We further cloned an ectodermal catalase, which shares 68% identity with mammalian monofunctional catalases. Last, 6 days of exposure of whole sea anemones to ATZ (0.5 mM) led to effective catalase inhibition and initiated symbiont expulsion. This demonstrates the crucial role of this enzyme in cnidarian bleaching, a phenomenon responsible for worldwide climate-change-induced mass mortalities, with catastrophic consequences for marine biodiversity