LincRNA_XR209691.3 could promote Bombyx mori nucleopolyhedrovirus replication by interacting with BmHSP70

Long non-coding RNAs (lncRNAs), a class of transcripts exceeding 200 nucleotides and lacking protein coding potential, have been proven to play important roles in viral infection and host immunity. Bombyx mori nucleopolyhedrovirus (BmNPV) is an important pathogen, which causes the silkworm disease and leads to a huge challenge to the sericultural industry. At present, research on the roles of insect lncRNAs in host-virus interaction are relatively few. In this study, we explored the function of lincRNA_XR209691.3 that was significantly up-regulated in the silkworm fat body upon BmNPV infection. Firstly, the subcellular localization experiment confirmed that lincRNA_XR209691.3 was present in both the nucleus and cytoplasm. Enhancing the expression of lincRNA_XR209691.3 in BmN cells could promote the proliferation of BmNPV, while inhibition of lincRNA_XR209691.3 by RNA interference suppresses the proliferation of BmNPV. Combining RNA pull-down and mass spectrometry, we identified the host and BmNPV proteins that could interact with lincRNA_XR209691.3. Next, by using truncation experiment and RNA immunoprecipitation (RIP) assay, it was found that lincRNA_XR209691.3 could bind to the Actin domain of BmHSP70. Subsequently, overexpression of lncRNA_XR209691.3 in BmN cells promoted the expression of BmHSP70, while knockdown of BmHsp70 suppressed the replication of BmNPV. Based on the above results, it is speculated that lincRNA_XR209691.3 could promote the proliferation of BmNPV through interaction with BmHSP70, possibly by improving the stability of BmHSP70 and thereby enhancing the expression of BmHSP70. Our results shed light on the lncRNA function in insect-pathogen interactions and provide a new clue to elucidate the molecular mechanism of BmNPV infection.