Pan-Transcriptome Analyses of Multiple Tissues and Growth Stages Create Expression Atlases for the Silkworm Bombyx mori

Transcriptome atlases can be used to examine the spatiotemporal dynamics of gene expression, thereby enabling the generation of genome-wide resources for understanding complex biological processes. In the silkworm Bombyx mori, transcriptomes serve as crucial datasets for elucidating the mechanisms underlying economically important traits. In this study, we integrated 832 transcriptome datasets across all developmental stages and tissues and performed whole-genome-scale transcriptome sequencing (RNAseq) on five critical tissues from silkworm strains Xian8 and 9211. We identified 5773 and 3323 housekeeping genes expressed across all developmental stages and tissues, respectively, and these genes were primarily enriched in cellular signaling, transport, structural organization, DNA repair, and RNA processing pathways. We also identified 27 stage-specific genes and 58 tissue-specific genes, providing candidate markers for future single-cell and spatial transcriptomics. A large number of alternative splicing events were detected from 832 NGS samples, indicating the critical roles of alternative splicing in silkworm development. Interestingly, only 10 long-read full-length transcriptome samples from Xian8 and 9211 yielded results comparable to the NGS in terms of novel genes and alternative splicing events, and these multi-tissue comparative analyses also revealed significant differences in alternative splicing patterns, underlining the necessity of long-read sequencing for such research. These datasets not only advance functional genomics research in Lepidoptera but also provide molecular signatures for silkworm strain-specific comparisons and association analyses with differential phenotypes. Silkworm pan-transcriptomics, by analyzing multidimensional transcriptional regulatory networks and gene-expression dynamics, can facilitate multidisciplinary integration and accelerate the breeding of high-yield and high-quality silkworm varieties.