Native-sized spider silk proteins synthesized in planta via intein-based multimerization

The synthesis of native-sized proteins is a pre-requisite for exploiting the potential of spider silkas a bio-based material. The unique properties of spider silk, such as extraordinary tensile strength and elasticity, result from the highly repetitive nature of spider silkprotein motifs. The present report describes the combination of spider silkflagelliform protein ( FLAG) production in the endoplasmic reticulum of tobacco plant leaf cells with an intein-based posttranslational protein fusion technology. The repeated ligation of FLAGmonomers resulted in the formation of large multimers. This method avoids the need for highly repetitive transgenes, which may result in a higher genetic and transcriptional stability. Here we show, for the first time, the production of synthetic, high molecular weight spider silkproteins larger than 250 kDa based on the assembly of protein monomers via intein-mediated trans-splicingin planta. The resulting multimeric structures form microfibers, thereby demonstrating their great potential as a biomaterial.