Molecular Cloning and Expression Analysis of Extra Sex Combs Gene during Development in Macrobrachium nipponense

The extra sex combs (Esc) gene first identified in Drosophia encodes a transcriptional repressor of homeotic genes belonging to the polycomb group (PcG) gene and is primarily expressed in the early embryos. In this study, we have isolated the full-length cDNA of an Esc gene from the testis of oriental river prawn (Macmbrachium nipponense) according to the established expressed sequence tags (ESTs) information using Rapid Amplification of the cDNA Ends (RACE) technique, designated as MnEsc. The full-length cDNA of MnEsc is 1,461bp in size and has an open reading frame (ORF) of 1,068bp, encoding a 355-amino acid protein. Real-time quantitative PCR analyses revealed that the expression level of MnEsc varied significantly in the developing embryo, postembryonic larval and adult tissues. Real-time quantitative PCR showed the MnEsc gene was expressed in testis, liver, ovary, brain, abdominal ganglion, heart, intestine and muscle with the highest level of expression in ovary and brain. In vivo silencing of the gene, the dsRNA of MnEsc caused a significantly decrease in target gene expression level in brain and ovary tissues, but no exterior appearance change of experimental shrimp was observed.