Integrated comparative genomic and transcriptomic analysis reveals a wsv249 mutation drives enhanced pathogenicity in white spot syndrome virus.

Abstract

Despite causing catastrophic losses across shrimp-farming regions worldwide, the molecular determinants that drive virulence differences among WSSV isolates remain poorly understood. Despite the remarkable conservation of WSSV genomes, outbreaks frequently exhibit differences in virulence among virus isolates. However, the molecular determinants underlying these differences remain unclear. This study aims to discover factors that enhance WSSV virulence and to elucidate the molecular mechanisms that regulate WSSV pathogenicity. Comparative genome analysis of four WSSV isolates from Thailand (SK1, SK2, CB1, and CB2) revealed that all isolates shared a highly conserved genome and structural stability. However, phylogenetic analysis revealed distinct evolutionary structuring, notably clustering SK1 and CB2 despite their different geographical origins. Infection experiments demonstrated differences in mortality rates among isolates, with the CB2 isolate exhibiting the highest mortality rate. Selection pressure analysis identified the immediate-early gene WSV249, encoding a RING finger E3 ubiquitin ligase, as positive selection (ω > 1) in high-virulence isolates. Functional validation through RNA interference (RNAi) targeting WSV249 resulted in 100% shrimp survival and a significant suppression of essential viral genes, including VP28 and thymidylate kinase. Furthermore, transcriptomic profiling revealed that WSV249 silencing prevented the host transcriptional disruption typically induced by WSSV, particularly in metabolic and immune-signaling pathways. These findings provide mechanistic insight into WSSV virulence determinants and identify WSV249 as a target for disease control strategies in shrimp aquaculture.