Regionalization of gene expression and cell types in the silk glands of <i>Plodia</i> pantry moths.

Abstract

Lepidopteran silk glands purportedly include a posterior silk gland (PSG) that secretes core fibers and a middle silk gland (MSG) that secretes adhesive sericins. While well-studied in the silkworm, little is known about other silk glands. Here, we used quantitative and spatial assays to profile gene expression in the silk glands of the pantry moth <i>Plodia interpunctella</i>. RNA-seq revealed the transcriptomic divergence between MSG and PSG. High expression of fibroin genes <i>FibL</i> and <i>FibH</i> was specific to the PSG, whereas the MSG was dominated by the expression of major sericins-bioadhesive proteins that coat the silk fiber. Hybridization chain reaction (HCR) mRNA profiling resolved sharp cellular boundaries within the silk gland: PSG cells expressed fibroins, while MSG cells comprised two compartments, each expressing different sericins. Our findings underscore the organization of lepidopteran silk glands into specialized secretory subdivisions and establish <i>Plodia</i> as a promising comparative model for studying silk diversity.