Sequence Characterization and Exploratory Expression Analysis of Five Candidate Immune-Related Genes in Tachypleus tridentatus Following WSSV Challenge

As a benthic inhabitant of coastal sediment habitats, Tachypleus tridentatus encounters fluctuating environmental conditions and diverse microorganisms and viruses, including WSSV. However, its molecular responses to white spot syndrome virus (WSSV) challenge remain poorly characterized. The three-spine horseshoe crab, Tachypleus tridentatus, is a marine chelicerate of interest for studies of invertebrate innate immunity. Herein, we characterize five immune-related genes identified as DEGs in Tachypleus tridentatus under WSSV stress by transcriptome analysis. The coding sequences of ARHGEF11, PAK1, MyD88, SOCS2 and SOCS5 were 1434, 897, 1005, 516 and 1347 bp long, respectively. These sequences encoded proteins of 477, 299, 334, 171 and 448 amino acids, respectively. Sequence analyses identified conserved features consistent with the corresponding protein families. ARHGEF11 expression increased from 9 h onward, and MyD88 reached its highest expression level at 48 h. PAK1 expression increased at early sampling times and subsequently declined. SOCS2 expression decreased from 9 h onward, whereas SOCS5 expression was higher than that in the control at early sampling times and lower from 12 h onward. However, SOCS5 expression already differed between groups at 0 h, limiting the attribution of this expression profile to WSSV challenge. These findings provide molecular resources and preliminary expression profiles for further studies of immunity in T. tridentatus.