Spider silks from plants – a challenge to create native‐sized spidroins

Abstract

Silk threads from spiders exhibit extraordinary mechanical properties, such as superior toughness and elasticity. Spider silks consist of several different large repetitive proteins that act as the basic materials responsible for these outstanding features. The production of spider silk protein variants in plants opens up new horizons in the production and functional investigation that enable the use of spider silks in innovative material development, nanotechnology and biomedicine in the future. This review summarizes and discusses production of spider silk protein variants in plants, especially with regards to plant expression systems, purification strategies, and characteristics of spider silk variants. Furthermore, the challenge of producing native-sized recombinant spidroins in planta is outlined, presenting three different strategies for achieving these high repetitive proteins with the help of non-repetitive C-terminal domains, crosslinking transglutaminase, and self-linking inteins. The potential of these fascinating proteins in medicine is also highlighted.

Plant Molecular Farming: Much More than Medicines

“…This allows them to fold and assemble complex proteins efficiently due to the presence of chaperones and protein disulfide isomerases that catalyze the formation of disulfide bonds, a capability not shared by bacterial production systems. This has proved invaluable for the production of pharmaceuticals, particularly multimeric proteins such as antibodies but also complex technical proteins such as collagen and spider silk (14)(15)(16)(17). The secretory pathway is also where posttranslational modifications (PTMs) are carried out, including glycosylation, γ-carboxylation, β-hydroxylation, amidation, proline hydroxylation, and sulfation (18,19).…”

“…The orb web spider Nephila clavipes produces different kinds of silk for webs, cocoons, and draglines. The dragline silk is five times stronger by weight than steel and three times tougher than p-aramid (Kevlar R ), one of the strongest man-made fibers (16). Silk proteins are challenging to express in microbes and mammalian cells because they are several hundred kilodaltons in size and cannot be secreted.…”

“…Scheller et al (82) were the first to produce spider silk proteins in plants, achieving yields of up to 2% TSP in tobacco leaves and potato tubers. Various strategies have been developed to ensure that recombinant silk proteins are produced at the correct native size, including dimerization by nonrepetitive C-termini, cross-linking by transglutaminase, and inteinmediated multimerization (16,83,84).…”

With great structure comes great functionality: Understanding and emulating spider silk

“…Other hosts such as plants 90 and mammalian cells 83,91 have also been demonstrated with silk constructs, yet these methods are also plagued with low expression levels and limitations in molecular weight. 52 Recent work using transgenic expression of ELPylated spider silk proteins in tobacco, however, appears to have overcome the problem of low molecular weight expression.…”

A Leishmania secretion system for the expression of major ampullate spidroin mimics

“…This approach, however, is dependent upon successful cloning of the highly-repetitive central block repeat coding regions and many researchers have addressed this complication by assembling multiple copies of synthetic block repeat domains [9,11]. These block repeat domains, alone and in various combinations with NTD and/or CTD, have been expressed in heterologous prokaryotic and eukaryotic expression systems including, but not limited to, bacteria [12,13], yeast [14], insect cell lines [15,16], and plants [9,17,18,19], albeit with varying levels of success. Most heterologous expression systems, however, have been plagued by low expression levels for a variety of reasons.…”