Targeting the circadian negative regulator period in Bombyx mori: a strategy for improving silk fibroin yield and mechanical properties

Abstract

Bombyx mori silk is a natural ultra-long protein fiber with a unique structure and extensive applications. Boosting production efficiency and innovating fiber performance represent critical industry needs as well as major technical bottlenecks. In this study, the mutant of the circadian negative regulator period (per) showed increased cocoon silk yield and fibroin content by 19.51% and 9.19%, respectively, and reduced silk fineness by 17.53%. Along with increased crystallinity and molecular orientation of fibroin fibers, the tensile strength and toughness of mutant cocoon silk were improved by 50.59% and 46.75%, respectively. Mechanistic analysis revealed that the per mutant displayed enhanced posterior silk gland development and fibroin synthesis, thereby increasing cocoon silk yield, particularly fibroin production efficiency. In parallel, the per mutant showed enhanced γ-aminobutyric acid (GABA)ergic signaling in the brain of its mature larvae, which was associated with suppressed downstream corazonin secretion and accelerated silk spinning. These findings in the per mutant suggest a promising strategy for targeting the circadian system to enhance fibroin production efficiency and mechanical properties of cocoon silk in B. mori.