Yorkie antagonizes innate antiviral immunity through regulating the IRF and Dorsal mediated antiviral pathways in Litopenaeus vannamei.

YORKIE: (Yki), a key effector of the Hippo signaling pathway, plays important roles in the regulation of cell proliferation and immune responses. In this study, two splice variants of the Yorkie gene (designated as LvYki-long and LvYki-short, respectively) were identified from Litopenaeus vannamei. The open reading frame (ORF) of LvYki-long is 1650 bp that encodes a putative protein of 549 amino acids. Compared with the amino acid sequence of LvYki-long, the amino acid sequence of LvYki-short is reduced by 78 amino acids (positions 416-493). Both LvYki-long and LvYki-short were universally expressed in all tested tissues. Following WSSV and DIV1 infection, their expression was significantly up-regulated in hemocytes and hepatopancreas but down-regulated in gills. The dsRNA-mediated knockdown of LvYki substantially enhanced the shrimp survival rate and reduced viral loads after WSSV and DIV1 infection. Besides, silencing of LvYki led to the down-regulation of Cactus, the up-regulation of Dorsal, as well as several AMPs (ALF1, ALF2, ALF4, and SWD3). Furthermore, silencing of LvYki also resulted in increased expression levels of Vago-JAK/STAT pathway components (Vago4, Vago5, and STAT), and the Co-IP results showed that LvYki could interact with LvIRF. The dual luciferase assay verified that LvYki significantly inhibited the activation of the Vago4 promoter by LvIRF. These results indicated that LvYki might antagonize the innate antiviral immunity through regulating the IRF and Dorsal-mediated antiviral pathways.