Silkworm PriS was specifically knocked out in the posterior silk gland, which reduced the internal replication of silk gland cells and promoted the process of apoptosis.

The silkworm is an important economic insect, and the silk gland is a crucial organ for synthesizing silk proteins. The development of the silk gland is vital for the synthesis and secretion of silk proteins, and the replication within the nucleus of silk gland cells is a significant characteristic of its development. Although it has been reported that Pris plays a role in the initiation of DNA replication, it remains unclear whether it functions in the nuclear replication of silk gland cells. In our study, we found that the expression of BmPris gradually increased in the late fifth instar silk glands, with relatively higher expression in the posterior silk glands. By utilizing gene editing technology to specifically knock out BmPris in the posterior silk glands, we observed a decrease in cocoon layer quantity and a thinning of the cocoon silk. Further dissection revealed that the posterior silk glands were absent in the BmPrisKO-PSG mutant compared to the wild type. Immunofluorescence staining indicated a significant reduction in the size of the posterior silk gland cells. Detection of intracellular protein content showed a significant decrease in silk fibroin proteins Ser1, 2, and 3. Edu staining revealed a significant reduction in replication within the posterior silk gland cells. Genes related to nuclear replication, MCM3, 5, 6, and 7, were all significantly downregulated. Cell cycle and proliferation-related genes CDK2, CyclinE, and Yki were significantly downregulated, while apoptosis-related genes Daxx and Dredd were significantly upregulated.