Blattella germanica displays a large arsenal of antimicrobial peptide genes

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.

Antimicrobial peptide expression in the cockroach gut during enterobacterial infection is specific and influenced by type III secretion

“…By extending recent in silico characterization of the innate immune repertoire of B. germanica ( Silva et al, 2020 ) in a functional direction, the work reported here provides new insight into the immunological adaptation of cockroaches to life in septic environments as well as the factors that regulate bacterial pathogen transmission by these insects.…”

“…Recent in silico analyses of the genomes of two synanthropic cockroach species, the American cockroach, Periplaneta americana , and the German cockroach, B. germanica, revealed an intriguing aspect of their immune systems ( Li et al, 2018 ; Silva et al, 2020 ). That is, when compared to distantly related holometabolous insects such as fruit flies and mosquitoes, both species encode an expanded arsenal of genes involved in the recognition and elimination of microbes.…”

“…The expansion of AMP genes is particularly striking in B. germanica . In this species, 39 putative AMP genes have been identified, among which are 16 Defensin-like genes, 13 Drosomycin-like genes, three Termicin like-genes, and seven Attacin-like genes ( Silva et al, 2020 ). Four of the Attacin-like genes identified in B. germanica encode proteins that are ∼200 amino acids in length and contain a glutamine/glutamic acid rich central region.…”

Of Cockroaches and Symbionts: Recent Advances in the Characterization of the Relationship between Blattella germanica and Its Dual Symbiotic System

“…A screening of AMP gene expression in B. germanica transcriptomic projects available in the NCBI database, corresponding to 28 whole-body samples from different developmental stages, tissues and body parts, confirmed that some AMPs are expressed specifically in some developmental stage [119]. In fact, the expression of the novel blattellicins is restricted to adult females, although the tissue in which they are expressed is unknown.…”

“…Although they are not complete yet, the genome projects of B. germanica [117] and P. americana [118] revealed that their repertoire of coding genes is larger than that of other related insects due to gene families' expansion, including some related to microbial defence and immune response. By integrating genomic and transcriptomic data, our group described 39 AMP-coding genes in B. germanica [119]. They belong to five families: defensins, termicins, drosomycins, attacins and blattellicins.…”