Shrimp Dscam and its cytoplasmic tail splicing activator serine/arginine (SR)-rich protein B52 were both induced after white spot syndrome virus challenge

The serine/arginine (SR)-rich protein family is phylogenetically conserved and plays significant roles in mRNA maturation, including alternative splicing (AS). In Drosophila, SR protein B52 functions as a splicing activator to regulate AS events in several genes, including the Down syndrome cell adhesion molecule (Dscam). In this study, the B52 gene from Litopenaeus vannamei (LvB52) was isolated and characterized. The open reading frame of LvB52 contains 1149 bp encoding 382 amino acids. The deduced LvB52 protein includes two RNA recognition motifs (RRM) at the N terminus and an arginine/serine rich domain (RS rich domain) at the C terminus, and thus shows the expected RRM1-RRM2-RS domain architecture. Tissue tropism analysis revealed that LvB52 is expressed in most tissues and at high levels in stomach and muscle. After white spot syndrome virus (WSSV) infection, a parallel increase in the expression of total LvDscam, tail-less LvDscam, membrane-bound LvDscam and LvB52 was observed after 24 hpi. Conversely, there was no obvious change in the expression of the AS repressor Lvhrp36. In vivo dsRNA silencing of LvB52 induced element 3 exclusion in the LvDscam cytoplasmic tail, but no abnormal exclusions in the Ig2-Ig3 region or the transmembrane region. We also found that the exon of the Ig7 region was quite often excluded, even in normal shrimp, and that LvB52 silencing was associated with a decrease in the variability of this region. Taken together, our data suggest that LvB52 acts as a splicing activator that regulates AS events in LvDscam.