A Polymorphic (CT)-SSR Influences the Activity of the Gene Implicated in Viral Resistance.

Simple sequence repeats (SSRs) of short nucleotide motifs occur very frequently in the 5' untranslated coding region (5'-UTR) of genes and have been implicated in the regulation of gene expression. In this study, we identified an SSR with a variable number of CT repeats in the 5'-UTR of the () gene that has been shown to mediate antiviral responses by inducing the expression of Vago, a functional homolog of mammalian IFN. We then explored the effects of varying the number of (CT) repeats on the expression of using both dual-luciferase reporter assays and Western blots. Our results demonstrate that the length of the (CT)-SSR in this gene can influence the expressional level of , in that a shorter (CT) repeat had a stronger ability to induce the expression of . Moreover, we found that the (CT) repeat in was associated with viral resistance in shrimp. Individual shrimps with shorter (CT) repeats in the 5'-UTR of exhibited high tolerance to white spot syndrome virus (WSSV), and this trait was inherited in offspring. Taken together, these results indicated that this (CT)-SSR could be used as a molecular marker for shrimp breeding for WSSV resistance.