Characterization of silk genes in Ephestia kuehniella and Galleria mellonella revealed duplication of sericin genes and highly divergent sequences encoding fibroin heavy chains

Abstract

Silk is a secretory product of numerous arthropods with remarkable mechanical properties. In this work, we present the complete sequences of the putative major silk proteins of E. kuehniella and compare them with those of G. mellonella, which belongs to the same moth family Pyralidae. To identify the silk genes of both species, we combined proteomic analysis of cocoon silk with a homology search in transcriptomes and genomic sequences to complement the information on both species. We analyzed structure of the candidate genes obtained, their expression specificity and their evolutionary relationships. We demonstrate that the silks of E. kuehniella and G. mellonella differ in their hydrophobicity and that the silk of E. kuehniella is highly hygroscopic. In our experiments, we show that the number of genes encoding sericins is higher in G. mellonella than in E. kuehniella. By analyzing the synteny of the chromosomal segment encoding sericin genes in both moth species, we found that the region encoding sericins is duplicated in G. mellonella. Finally, we present the complete primary structures of nine fibH genes and proteins from both families of the suborder Pyraloidea and discuss their specific and conserved features. This study provides a foundation for future research on the evolution of silk proteins and lays the groundwork for future detailed functional studies.

Unravelling the complexity of silk sericins:P150/sericin 6is a new silk gene inBombyx mori

“…A previous study on the pyralid moths G. mellonella and E. kuehniella showed that the known sericin genes, with the exception of P150/ser6, lie within the cluster of orthologous genes in the corresponding chromosomal regions [14]. Such microsynteny can be also observed between B. mori and G. mellonella or E. kuehniella (Fig 5).…”

“…Such microsynteny can be also observed between B. mori and G. mellonella or E. kuehniella (Fig 5). The results also show a number of local rearrangements and duplications in this region including the expansion of several sericin genes in G. mellonella compared to related moths [14].…”

“…The best results are obtained by comparing genomic and cDNA sequences or by using proteomic data [30]. Previous identification of P150/ser6 sequences in G. mellonella and E. kuehniella was successfully performed using this approach [13, 14]. In contrast, finding the B. mori P150/ser6 homolog has been more difficult due to its relatively low expression.…”

“…The genome assemblies and annotated information of B. mori (GCF_014905235.1), E. kuehniella [14,21], and G. mellonella (GCF_026898425.1) were processed and submitted to the GENESPACE software [22] for syntenic analysis. Plots showing the microsyntenic relationships were then generated based on the best mutual hits between the three species and visualized using the R package ggplot2 [23].…”

“…The presence of Ser2, Ser4, and Ser5 in non-cocoon silks suggests that they may have a specific function during these developmental stages. In this study, we describe another adhesive protein from B. mori silk that is homologous to a previously identified sericin-like protein, P150, found in the larval cocoons of G. mellonella and Ephestia kuehniella (superfamily Pyraloidea) [13, 14].…”