Dynamic immune and metabolism response of clam Meretrix petechialis to Vibrio challenge revealed by a time series of transcriptome analysis.

Meretrix petechialis is an important commercial aquaculture species in China. During the clam culture period, mass mortality events often occurred due to the Vibrio infection. In this paper, M. petechialis were challenged with Vibrio parahaemolyticus immersion to simulate a natural infection, and the infection process were divided into four phases including latency, prodrome, onset and recovery phases based on the clam mortality data. Then, the dynamic response of clams to Vibrio infection at different infection phases were investigated by transcriptome analysis. A total of 38,067 differentially expressed genes (DEGs) were identified at different infection phases. DEG annotations showed that immune-related and metabolism-related signaling pathways were enriched, indicating that immune defense and metabolism process play key roles during bacterial infection. Three kinds of expression pattern were classified by cluster analysis, including U-shape, L-shape and inverted V-shape. Anabolism and cellular growth proliferation related signaling pathways were repressed (long-lasting or transient) during bacterial infection. However, the immune related signaling pathways with different immune functions showed induction expression or repression expression against bacterial infection, which indicated that immune system take different strategies against bacterial infection. Furthermore, some signaling pathways such as PI3K-Akt signaling pathway both involved in immune defense and cell metabolism. This study provides a sight that the dynamic immunity and metabolic responses may be integrated to improve the host survival and shift more energy for immune defense.