Blattella germanica displays a large arsenal of antimicrobial peptide genes

Francisco J Silva,Amparo Latorre,Maria Muñoz-Benavent,Carlos García-Ferris

doi:10.1038/s41598-020-77982-3

Abstract

Defence systems against microbial pathogens are present in most living beings. The German cockroach Blattella germanica requires these systems to adapt to unhealthy environments with abundance of pathogenic microbes, in addition to potentially control its symbiotic systems. To handle this situation, four antimicrobial gene families (defensins, termicins, drosomycins and attacins) were expanded in its genome. Remarkably, a new gene family (blattellicins) emerged recently after duplication and fast evolution of an attacin gene, which is now encoding larger proteins with the presence of a long stretch of glutamines and glutamic acids. Phylogenetic reconstruction, within Blattellinae, suggests that this duplication took place before the divergence of Blattella and Episymploce genera. The latter harbours a long attacin gene (pre-blattellicin), but the absence of the encoded Glx-region suggests that this element evolved recently in the Blattella lineage. A screening of AMP gene expression in available transcriptomic SR projects of B. germanica showed that, while some AMPs are expressed during almost the whole development, others are restricted to shorter periods. Blattellicins are highly expressed only in adult females. None of the available SR tissue projects could be associated with blattellicins’ expression, suggesting that it takes place in other tissues, maybe the gut.

Highlights

A complex pattern with some antimicrobial peptides (AMPs) gene products acting on reduced number of species, while others having a taxonomically broader e ffect[10]
The expression of each AMP gene may occur during the whole development or may be restricted to some stages, as it is the case of blattellicins
The first was the search for product names including the terms defense, drosomycin, tenecin, phormicin, attacin and coleoptericin

Summary

Introduction

A complex pattern with some AMP gene products acting on reduced number of species, while others having a taxonomically broader e ffect[10]. Permeabilization of symbiont membranes to solve the problem of the transport of metabolites between host cells and endosymbionts through sublethal AMP doses was suggested[15]. B. germanica harbours specialized cells in the fat body, named bacteriocytes, which contain thousands of cells of the bacterial endosymbiont Blattabacterium cuenoti (hereafter, Blattabacterium). This symbiotic relationship is at least 150 My old and, with the exception of some endosymbiont losses, Blattabacterium and Blattodea hosts have been co-evolving since [16,17,18,19]. We have carried out a thorough characterization of B. germanica AMPs describing 39 genes including an unusual Glx-rich new attacin-derived type that we have called blattellicin. The expression of each AMP gene may occur during the whole development or may be restricted to some stages, as it is the case of blattellicins

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Conclusion