Sericin Composition in the Silk of Antheraea yamamai

Abstract

The silks produced by caterpillars consist of fibroin proteins that form two core filaments, and sericin proteins that seal filaments into a fiber and conglutinate fibers in the cocoon. Sericin genes are well-known in Bombyx mori (Bombycidae) but have received little attention in other insects. This paper shows that Antheraea yamamai (Saturniidae) contains five sericin genes very different from the three sericin genes of B. mori. In spite of differences, all known sericins are characterized by short exons 1 and 2 (out of 3-12 exons), expression in the middle silk gland section, presence of repeats with high contents of Ser and charged amino acid residues, and secretion as a sticky silk component soluble in hot water. The B. mori sericins represent tentative phylogenetic lineages (I) BmSer1 and orthologs in Saturniidae, (II) BmSer2, and (III) BmSer3 and related sericins of Saturniidae and of the pyralid Galleria mellonella. The lineage (IV) seems to be limited to Saturniidae. Concerted evolution of the sericin genes was apparently associated with gene amplifications as well as gene loses. Differences in the silk fiber morphology indicate that the cocktail of sericins linking the filaments and coating the fiber is modified during spinning. Silks are composite biomaterials of conserved function in spite of great diversity of their composition.

The genome sequence of Samia ricini, a new model species of lepidopteran insect

“…Regarding sericin genes in Papilio xuthus , no sequences were previously registered in GenBank, and thus the same procedure as in Plutella xylostella and D. plexippus was taken. Phylogenetic analysis of sericin was conducted with seven S. ricini putative sericin genes, three B. mori sericin genes and five A. yamamai sericin genes (LC08587, LC08588, LC08589, LC08590 and LC08591; Zurovec et al., 2016). muscle was used to generate alignments of protein sequences (Edgar, 2004).…”

Expansion of Imaginal Disc Growth Factor Gene Family in Diptera Reflects the Evolution of Novel Functions

“…Total RNA samples from dissected larval silk glands of Tineola bisselliella , Acanthobrahmaea europaea , Hepialus humuli , Eumeta pryeri , Yponomeuta cagnagella , Thaumatopoea pithyocampa , Plectrocnemia conspersa , Phyllonorycter roboris , Lymantria dispar , Andraca theae (Order Lepidoptera), and Hydropsyche angustipennis (Order Trichoptera) were extracted using Trizol reagent (Life Technologies, Carlsbad, CA, USA) and used to prepare cDNA libraries for the Illumina sequencing platform, as described previously [13]. In addition, cDNA libraries from four other lepidopteran species, Malacosoma neustria , Lasiocampa quercus , Arctia caja , and Bena prasinana , as well as two caddisflies, Oligotricha striata and Rhyacophila obliterate (Order Trichoptera), were sequenced using Roche/454 sequencing technology, as described earlier [14]. A RiboMinus Eukaryote Kit for RNA-Seq (Ambion, Austin, TX, USA) was used to remove rRNA, after which the poly-A mRNA was enriched with the aid of a Dynabeads Oligo (dT) 25 mRNA Purification Kit (Thermo Fisher Scientific, Waltham, Ma, USA), and the cDNA library was created with a NEXTflex Rapid RNA-Seq Kit (Bioo Scientific, Austin, TX, USA), as described earlier [13].…”

Genome sequence of the Japanese oak silk moth, Antheraea yamamai: the first draft genome in the family Saturniidae

“…Merged and spliced gene structured were corrected by comparing the gene structure with known exon structure in the NCBI NR database. In addition, fibroin and sericin genes, which couldn’t be properly predicted because of their high repeat motif, were also manually identified with previously known sequences [ 42 , 52 ] with RNA-seq data. The final gene set of the A. yamamai genome contains 15 481 genes.…”