Spatzle, a signaling molecule that interacts with pathogen-associated molecules and Toll-like receptor in Portunus trituberculatus

Spatzle is a crucial ligand for Toll-like receptor (TLR) that triggers the activation of TLR signal pathway in in-sects. In this study, open reading frames (ORFs) of two spa spacing diaeresis tzles were cloned from Portunus trituberculatus (PtSpz1 and PtSpz2). Both of PtSpzs contained the typical cystine-knot domain of spa spacing diaeresis tzle. Tissue distribution analysis showed that both of PtSpzs were predominantly expressed in the gills. Transcriptional levels of the two PtSpzs in hemocytes and gill rapidly increased at 3 h and 6 h post Vibrio alginolyticus challenge, respectively. The two PtSpzs could bind to several pathogen-associated molecules including lipopolysaccharide (LPS), peptidoglycan (PGN) and envelope proteins of white spot syndrome virus (WSSV). Moreover, the two PtSpzs could directly interact with the extracellular leucine-rich repeats (LRR) domain of TLR. This study revealed that spa spacing diaeresis tzle could interact with pathogen-associated molecules and TLR of host, which may be two important steps for spa spacing diaeresis tzle to deliver signals into host cells.