The Hippo-Yki pathway governs growth and cell fate in the posterior silk gland of the silkworm.

The posterior silk gland (PSG) of the silkworm (Bombyx mori) is a specialized organ that synthesizes vast quantities of silk fibroin; however, the cell-type-specific mechanisms regulating its development remain largely unclear. Leveraging our previously constructed single-cell atlas, we performed high-dimensional weighted gene coexpression network analysis (hdWGCNA). The analysis revealed a gene module strongly correlated with fibroin-synthesizing cells (FBSs) in the PSG. Pathway analysis revealed significant enrichment of the Hippo signaling pathway within this module, with its downstream transcriptional coactivator, Yorkie (Yki), being identified as a top-ranked hub gene. Strikingly, PSG-specific Yki overexpression or knockdown induced severe developmental defects from early larval stages. Transcriptomic profiling combined with cellular deconvolution demonstrated that Yki is essential for maintaining the transcriptional identity and proportional homeostasis of the FBS population. Our study establishes the Hippo-Yki pathway as a central developmental regulator that coordinates organ growth and FBS fate specification in the silk gland, offering new genetic insights into potential targets for improving silk production.