Altering of host larval (Spodoptera exigua) calcineurin activity in response to ascovirus infection

• Published in: Pest management science 2020-03, Vol.76 (3), p.1048-1059
• Main Authors: Yu, Huan, He, Lei, Li, Zi‐Qi, Li, Ni, Ou‐Yang, Yi‐Yi, Huang, Guo‐Hua
• Format: Article
• Language: English
• Subjects: Acid phosphatase; Animals; Ascoviridae; ascovirus; Calcineurin; Calcium ions; Calcium signalling; CaN subunit; Gene expression; Heliothis virescens ascovirus 3h; HvAV‐3h; Immunoblotting; Immunoprecipitation; Infections; Inhibitors; insect calcineurin; Larva; Larvae; Organic chemistry; Phosphatase; PP2B; Replication; Signal processing; Signal transduction; Spodoptera; Spodoptera exigua; Transcription
• ISSN: 1526-498X; 1526-4998
• DOI: 10.1002/ps.5615

BACKGROUND Calcineurin (CaN) is involved in numerous cellular processes and Ca2+‐dependent signal transduction pathways. According to our previous transcriptome studies, thousands of host larval (Spodoptera exigua) transcripts were downregulated after the infection of Heliothis virescent ascovirus 3h (HvAV‐3h), while the Spodoptera exigua calcineurin genes (SeCaNs) were significantly upregulated. To understand the regulation of SeCaNs in S. exigua larvae during the infection of HvAV‐3h, the functions of CaN subunit A (SeCaN‐SubA) and CaN binding protein (SeCaN‐BP) were analysed. RESULTS The in vitro assays indicated that the bacterial expressed SeCaN‐SubA is an acid phosphatase, but no phosphatase activity was detected with the purified SeCaN‐BP. The transcription level of SeCaN‐SubA was upregulated after HvAV‐3h infection and the CaN activity was significantly increased after HvAV‐3h infection in S. exigua larvae. Interestingly, the SeCaN‐BP transcripts were only detectable in the HvAV‐3h infected larvae. Further immunoblotting results consistently agree with those obtained by qPCR, indicating that the infection of HvAV‐3h causes the upregulated expression of SeCaN‐SubA and the appearance of SeCaN‐BP. An interaction between the cleaved SeCaN‐SubA and SeCaN‐BP was detected by co‐immunoprecipitation assays, and the expression of SeCaN‐BP in Spodoptera frugiperda‐9 (Sf9) cells can help to increase the CaN activity of SeCaN‐SubA. Further investigations with CaN inhibitors suggested that HvAV‐3h. Further investigations with CaN inhibitors suggested that the inhibition on host larval CaN activity can also inhibit the viral replication of HvAV‐3h. CONCLUSION The increase in CaN activity caused by HvAV‐3h infection might be due to the upregulation of SeCaN‐SubA and the induced expression of SeCaN‐BP, and increased CaN activity is essential for ascoviral replication. © 2019 Society of Chemical Industry The function of calcineurin subunits was characterized in this study, providing a detailed insight into the regulation strategy of Spodoptera exigua during the Heliothis virescens ascovirus 3h infection.