Although the mollusc immune system has been studied at the cellular level, the response
to pathogens at gene expression level has not been thoroughly investigated. This study
aimed to investigate the early molecular response of hemocytes of soft-shell clams,
Mya arenaria, to Vibrio splendidus strain LGP32 by identification of transcripts involved
in immune defense. The Suppression Subtractive Hybridization (SSH) was used to selectively
identify differentially expressed genes in hemocytes exposed to V. splendidus at a
ratio 1:1 for 2 h. Both forward and reverse subtracted cDNA were constructed and a
total of 16,000 reads were obtained and analyzed. Identity searches in genome databases
were performed using BlastX program and transcripts were clustered to cellular functions
including structural proteins, immunity, stress proteins, apoptosis, cell process,
metabolism and signal transduction. Among the differentially expressed immune associated
genes were ficolin, killer cell lectin-like receptor, natural resistance-associated
macrophage protein 1 (Nramp-1), mitogen-activated protein kinases (MAPK), ferritin,
heat shock proteins 90 (HSP90) and cathepsin and their expressions were quantified
using Reverse Transcription quantitative Polymerase Chain Reaction (RT-qPCR) at 1,
2 and 3 h post-Vibrio challenge. These genes showed similar expression patterns, up-regulation
at 1 h, followed by a down-regulation at 2 and 3 h. These data corroborates our previous
observations of cell rounding, reduced phagocytosis and respiratory burst activity.
To our knowledge, this is the first study to demonstrate an effect of V. splendidus
on expression of genes related to immune system in soft-shell clams M. arenaria. However,
further investigations are needed to unravel the molecular mechanisms of hemocytes
subjected to V. splendidus.
Copyright 2010. Published by Elsevier Ltd.