The Involvement of LvSRSF2 in Circular RNA Biogenesis and Its Role in Immunity Against White Spot Syndrome Virus...

Serine/arginine splicing factors (SRSFs) are critical regulators of gene expression that influence alternative splicing through RNA binding via the RNA recognition motif (RRM). Circular RNAs (circRNAs) are a subset of non-coding RNAs that exhibit differential expression in WSSV-infected Litopenaeus vannamei. This study investigates the role of LvSRSF2 in regulating circRNA expression in response to WSSV infection. LvSRSF2 was highly expressed in hemocytes and upregulated during WSSV infection. Silencing LvSRSF2 using dsRNA significantly upregulated the expression of circRNAs (circ-Alpha2, circ-Anillin, circ-Hemocytin, circ-Nephrin, and circ-Toll) in both WSSV-infected and uninfected shrimps at 72 h post-injection with dsRNAs. Knockdown of LvSRSF2 also significantly reduced WSSV copy numbers at 24 h post-infection and extended shrimp survival, with knockdown shrimp surviving up to 9 d compared to the control group. In addition, circ-Hemocytin, an SRSF2-related circRNA, was predicted to interact with six miRNAs targeting immune-related genes such as Toll, STAT, NF-κB, and Vago4. Following WSSV infection, circ-Hemocytin expression increased at 24 and 48 hpi, and the immune genes STAT and Vago4 were also upregulated, suggesting a potential circRNA-miRNA-mRNA regulatory axis in shrimp antiviral defense. Furthermore, targeted suppression of circ-Hemocytin expression using siRNAs significantly reduced its expression without affecting the corresponding linear transcript and resulted in a notable decrease in WSSV load in shrimp gills, highlighting its potential role in antiviral defense.