High mechanical property silk produced by transgenic silkworms expressing the spidroins PySp1 and ASG1

Xiaoli Tang,Xiaogang Ye,Boxiong Zhong,Shuo Zhao,Xiaoxiao Wang,Meiyu Wu,Jinghua Ruan

doi:10.1038/s41598-021-00029-8

Abstract

Spider silk is one of the best natural fibers with excellent mechanical properties; however, due to the visual awareness, biting behavior and territory consciousness of spiders, we cannot obtain spider silk by large-scale breeding. Silkworms have a spinning system similar to that of spiders, and the use of transgenic technology in Bombyx mori, which is an ideal reactor for producing spider silk, is routine. In this study, the piggyBac transposon technique was used to achieve specific expression of two putative spider silk genes in the posterior silk glands of silkworms: aggregate spider glue 1 (ASG1) of Trichonephila clavipes (approximately 1.2 kb) and two repetitive units of pyriform spidroin 1 (PySp1) of Argiope argentata (approximately 1.4 kb). Then, two reconstituted spider silk-producing strains, the AG and PA strains, were obtained. Finally, the toughness of the silk fiber was increased by up to 91.5% and the maximum stress was enhanced by 36.9% in PA, and the respective properties in AG were increased by 21.0% and 34.2%. In summary, these two spider genes significantly enhanced the mechanical properties of silk fiber, which can provide a basis for spidroin silk production.

Highlights

Spider silk is one of the best natural fibers with excellent mechanical properties; due to the visual awareness, biting behavior and territory consciousness of spiders, we cannot obtain spider silk by large-scale breeding
The key expression boxes included the polyA sequence of the Fibroin-heavy chain (Fib-H) gene, which was under the control of a Fib-H promoter sequence; two repeats of pyriform spidroin 1 (PySp1) (1.4 kb, Supplementary Fig. S1) or one repeat of aggregate spider glue 1 (ASG1) (1.2 kb, Supplementary Fig. S2), whose protein MWs were predicted to be 50 kDa and 45 kDa, respectively; and enhanced green fluorescence protein (EGFP) as the marker gene for screening positive individuals, which was induced by the IE1 promoter for nonspecific expression in the whole body
To obtain more stable transgenic strains, the G1 PA and AG moths were mated with wild-type moths to produce the G2 generation (PA; AG)

Summary

Introduction

Spider silk is one of the best natural fibers with excellent mechanical properties; due to the visual awareness, biting behavior and territory consciousness of spiders, we cannot obtain spider silk by large-scale breeding. Spidroins are composed of many specific repetitive units or motifs with large molecular weights, and these motifs are considered the basis for the unique mechanical properties of spider silk. Previous studies have identified the sequence of aggregate silk glue genes (ASG1 and ASG2) of the golden orb-weaving spider T. clavipes[14] and reported that there are no repetitive fragments and that the motifs are NVNVN and Q PGSG15, which differ from those of MiSp, MaSp and Flag. These different motifs contribute to the specific properties of pyriform and aggregate silk. The strength or toughness of silk fibers obtained by these methods was improved; for large-scale production, these methods are time-consuming and expensive

Methods

Results

Conclusion