Molecular characterization of four differentially expressed genes during planktonic stages in Chinese mitten crab, Eriocheir sinensis

Abstract

The molecular markers to distinguish different larval stage have various applications in ecological study. Using differential display RT-PCR technique, we isolated and characterized four genes, which are expressed predominantly in megalopa in Eriocheir sinensis. Four genes include two cuticular proteins with different domain organization (Ers-CP15 and Ers-CP34) and two muscular tissue-specific genes (Ers-SCP and Ers-ActinSK1). Two culticular protein genes were expressed predominantly in epidermis and their expression level was significantly high in megalopa stage (about 7-folds) compared with those in zoea stage. However, their high transcriptional level in zoea IV suggested that two culticular protein genes may not be a useful target to discriminate megalopa from zoea. Ers-SCP encoded the invertebrate-specific sarcoplasmic calcium binding protein and Ers-ActinSK1 gene encoded crustacean skeletal muscle actin. Expressions of both genes were detected only in muscular tissues including leg muscle, claw muscle, and thoracic muscle suggesting increased transcription level of two muscle-specific genes during megalopa stage is mainly due to the increased muscular tissues. Among its three isoforms, Ers-SCPa showed the highest difference (22.4-folds) between megalopa and zoea suggesting Ers-SCPa is the most reliable marker to distinguish megalopa from zoea. Although Ers-SCPc and Ers-ActinSK1 also showed similar expression profile to Ers-SCPa and Ers-SCPb, difference of their expression level was not as high as Ers-SCPa and Ers-SCPb.