Identification and functional study of Fib‐L, a major silk fibroin gene component in rice leaf folders

Abstract The rice leaf folder, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae), is a major migratory pest in rice agriculture. This pest is characterised by its larvae's ability to fold rice leaves using silk, a behaviour that culminates in the formation of a silken cocoon during the pupal stage. The fibroin light chain ( CmFib‐L ) gene is crucial for silk production, yet its specific function in C . medinalis has reminded elusive. This study presents a comprehensive analysis of the CmFib‐L gene, revealing its complete open reading frame (ORF) and expression patterns. Notably, the gene is highly expressed in the fifth‐instar larvae and the silk gland, which are critical stages for silk production. Our experiments demonstrate that silencing the CmFib‐L gene leads to a reduction in pupal weight, an extension of the pupal stage and a disorganised silk cocoon. Furthermore, the larval behaviour of leaf folding and spinning is significantly impaired when the expression of CmFib‐L is downregulated. These findings not only show the importance of fibroin light chain in silk production but also reveal a new target gene to regulate and control the behaviour and development of C. medinalis .