title: Systemic infection generates a local-like immune response of the bacteriome organ in insect symbiosis.
abstract: Endosymbiosis is common in insects thriving in nutritionally unbalanced habitats. The cereal weevil, Sitophilus oryzae, houses Sodalis pierantonius, a Gram-negative intracellular symbiotic bacterium (endosymbiont), within a dedicated organ called a bacteriome. Recent data have shown that the bacteriome expresses certain immune genes that result in local symbiont tolerance and control. Here, we address the question of whether and how the bacteriome responds to insect infections involving exogenous bacteria. We have established an infection model by challenging weevil larvae with the Gram-negative bacterium Dickeya dadantii. We showed that D. dadantii infects host tissues and triggers a systemic immune response. Gene transcript analysis indicated that the bacteriome is also immune responsive, but it expresses immune effector genes to a lesser extent than the systemic and intestinal responses. Most genes putatively involved in immune pathways remain weakly expressed in the bacteriome following D. dadantii infection. Moreover, quantitative PCR experiments showed that the endosymbiont load is not affected by insect infection or the resulting bacteriome immune activation. Thus, the contained immune effector gene expression in the bacteriome may prevent potentially harmful effects of the immune response on endosymbionts, whilst efficiently protecting them from bacterial intruders.
authors: Biologie Fonctionnelle Insectes et Interactions, UMR203 BF2I, INRA, INSA-Lyon, Université de Lyon, Villeurbanne, France.
authors: Florent
authors: F
authors: Masson
authors: Agnès
authors: A
authors: Vallier
authors: Aurélien
authors: A
authors: Vigneron
authors: Séverine
authors: S
authors: Balmand
authors: Carole
authors: C
authors: Vincent-Monégat
authors: Anna
authors: A
authors: Zaidman-Rémy
authors: Abdelaziz
authors: A
authors: Heddi
mesh_terms: D000818:Animals; D015964:Gene Expression Regulation, Bacterial / Q000276:immunology*; D006090:Gram-Negative Bacteria / Q000276:immunology*; D013559:Symbiosis / Q000276:immunology*; D048889:Weevils / Q000276:immunology* / Q000382:microbiology*
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