The architecture of silk-secreting organs during the final larval stage of silkworms revealed by single-nucleus and spatial transcriptomics.

Natural silks are renewable proteins with impressive mechanical properties and biocompatibility that are useful in various fields. However, the cellular and spatial organization of silk-secreting organs remains unclear. Here, we combined single-nucleus and spatially resolved transcriptomics to systematically map the cellular and spatial composition of the silk glands (SGs) of mulberry silkworms late in larval development. This approach allowed us to profile SG cell types and cell state dynamics and identify regulatory networks and cell-cell communication related to efficient silk protein synthesis; key markers were validated via transgenic approaches. Notably, we demonstrated the indispensable role of the ecdysone receptor (ultraspiracle) in regulating endoreplication in SG cells. Our atlas presents the results of spatiotemporal analysis of silk-secreting organ architecture late in larval development; this atlas provides a valuable reference for elucidating the mechanism of efficient silk protein synthesis and developing sustainable products made from natural silk. [Display omitted] • Cell-type distribution and spatial organization in silkworm silk glands were mapped • Spatiotemporal gene expression patterns in the silk glands of late larvae were profiled • The characteristics and roles of types of cells in silk protein synthesis were analyzed • Resources were applied to explore the cell biology of silk-secreting organs Ma et al. present a spatiotemporal transcriptomic map of silkworm silk-secreting organs. This atlas provides insights into cellular heterogeneity, dynamic changes in the cell state, regulatory networks, and endoreplication regulation in silk glands, as well as a framework for high-resolution exploration of the mechanism of efficient silk protein synthesis. [ABSTRACT FROM AUTHOR]