Darwin’s bark spider shares a spidroin repertoire with Caerostris extrusa but achieves extraordinary silk toughness through gene expression

Abstract

Spider silk is a protein-based material whose toughness suggests possible novel applications. A particularly fascinating example of silk toughness is provided by Darwin's bark spider (Caerostris darwini) found in Madagascar. This spider produces extraordinarily tough silk, with an average toughness of 350 MJ/m and over 50% extensibility, and can build river-bridging webs with a size of 2.8 m2. Recent studies have suggested that specific spidroins expressed in C. darwini are responsible for the mechanical properties of its silk. Therefore, a more comprehensive investigation of spidroin sequences, silk thread protein contents, and phylogenetic conservation among closely related species is required. Here, we conducted genomic, transcriptomic, and proteomic analyses of C. darwini and its close relative Caerostris extrusa. A variety of spidroins and low-molecular-weight proteins were found in the dragline silk of these species; all of the genes encoding these proteins were conserved in both genomes, but their genes were more expressed in C. darwini. The potential to produce very tough silk is common in the genus Caerostris, and our results may suggest the existence of plasticity allowing silk mechanical properties to be changed by optimizing related gene expression in response to the environment.

Composition of minor ampullate silk makes its properties different from those of major ampullate silk

“…Sample preparation for proteome analysis of MA-silk and MI-silk was performed as previously described. 41 Briefly, reeled silk samples were immersed in 6 M guanidine-HCl buffer (pH 8.5) for MA-silk and 9 M LiBr for MI-silk, followed by freezing and freezing in liquid nitrogen. The samples were thawed and subjected to sonication using a Bioruptor II (BM Equipment Co., Ltd.) for protein extraction.…”

Chromosome-level genome and the identification of sex chromosomes in Uloborus diversus

“…Spider genomes are enormous with high repeat content, making them challenging to assemble(Sanggaard et al 2014; Stellwagen and Renberg 2019; Ayoub et al 2013). While 22 spider genomes have been assembled and made publicly available(Sanggaard et al 2014; Babb et al 2017; Kono et al 2019; Sheffer et al 2021; Sánchez-Herrero et al 2019; Schwager et al 2017; Fan et al 2021; Yu et al 2019; Liu et al 2019; Escuer et al 2022; Cerca et al 2021; Zhu et al 2022; Hendrickx et al 2022; Kono et al 2021a; Purcell and Pruitt 2019; Li et al 2022; Kono et al 2021b) ( Table S1 ), most are highly fragmented, with 6 assembled to chromosome-scale(Sheffer et al 2021; Fan et al 2021; Escuer et al 2022; Zhu et al 2022; Hendrickx et al 2022; Kono et al 2021b). Of the 22 genomes, only 7 represent the Araneoidea(Kono et al 2019; Sheffer et al 2021; Fan et al 2021; Kono et al 2021a) or ecribellate orb-weavers, 2 of which have been assembled to chromosome-scale(Sheffer et al 2021; Fan et al 2021).…”