Zinc finger protein RP-8, the Bombyx mori ortholog of programmed cell death 2, regulates cell proliferation

Programmed cell death 2 (PDCD2) is a highly conserved eukaryotic protein indispensable for various physiological processes such as cell proliferation, development, and apoptosis. In the present study, we identified a Zinc finger protein RP-8 from the silkworm, Bombyx mori (BmZfrp8), the ortholog of PDCD2 protein. The quantitative real-time PCR analysis revealed the ubiquitous distribution of BmZfrp8 in the different tissues; however, the gene's transcription level was highest in those of the silk gland, testis, and ovary. Additionally, the expression levels of BmZfrp8 were unequal on different days of embryonic development, and it reached the highest level on the 5th day of early development. The challenge with pathogens influenced the expression level of BmZfrp8 in both hemocyte and fat body when compared with the control. Administration of 20-hydroxyecdysone significantly enhanced the BmZfrp8 expression in hemocyte. The knock-down of BmZfrp8 by double-stranded RNA suppressed the expression of developmental pathway associated genes as well as cell cycle-associated genes. Furthermore, the RNAi treated cells also showed cell cycle arrest compared to the control group. Taken together, BmZfrp8 may have a critical biological role in of B. mori, since it regulates the expression of the developmental pathway and cell cycle-associated genes.