title: Antimicrobial peptides and cell processes tracking endosymbiont dynamics.
abstract: Many insects sustain long-term relationships with intracellular symbiotic bacteria that provide them with essential nutrients. Such endosymbiotic relationships likely emerged from ancestral infections of the host by free-living bacteria, the genomes of which experience drastic gene losses and rearrangements during the host-symbiont coevolution. While it is well documented that endosymbiont genome shrinkage results in the loss of bacterial virulence genes, whether and how the host immune system evolves towards the tolerance and control of bacterial partners remains elusive. Remarkably, many insects rely on a 'compartmentalization strategy' that consists in secluding endosymbionts within specialized host cells, the bacteriocytes, thus preventing direct symbiont contact with the host systemic immune system. In this review, we compile recent advances in the understanding of the bacteriocyte immune and cellular regulators involved in endosymbiont maintenance and control. We focus on the cereal weevils Sitophilus spp., in which bacteriocytes form bacteriome organs that strikingly evolve in structure and number according to insect development and physiological needs. We discuss how weevils track endosymbiont dynamics through at least two mechanisms: (i) a bacteriome local antimicrobial peptide synthesis that regulates endosymbiont cell cytokinesis and helps to maintain a homeostatic state within bacteriocytes and (ii) some cellular processes such as apoptosis and autophagy which adjust endosymbiont load to the host developmental requirements, hence ensuring a fine-tuned integration of symbiosis costs and benefits.This article is part of the themed issue 'Evolutionary ecology of arthropod antimicrobial peptides'.
authors.affiliation: Université de Lyon, INSA-Lyon, INRA, BF2I, UMR0203, 69621 Villeurbanne, France.
authors.forename: Florent
authors.identifier: 0000-0002-5828-2616
authors.initials: F
authors.lastname: Masson
authors.affiliation: Université de Lyon, INSA-Lyon, INRA, BF2I, UMR0203, 69621 Villeurbanne, France.
authors.forename: Anna
authors.identifier: 0000-0003-2550-1752
authors.initials: A
authors.lastname: Zaidman-Rémy
authors.affiliation: Université de Lyon, INSA-Lyon, INRA, BF2I, UMR0203, 69621 Villeurbanne, France abdelaziz.heddi@insa-lyon.fr.
authors.forename: Abdelaziz
authors.identifier: 0000-0001-6708-9298
authors.initials: A
authors.lastname: Heddi
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis; D001343:Autophagy; D018407:Bacterial Physiological Phenomena; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D013559:Symbiosis; D048889:Weevils / Q000235:genetics / Q000276:immunology / Q000382:microbiology* / Q000502:physiology*
chemical_list: D023181:Antimicrobial Cationic Peptides; D019476:Insect Proteins
keywords: Coleoptericin; Sitophilus; antimicrobial peptide; bacteriocyte; endosymbiosis