Transcriptomic Characterization of the Early Development Stages in Pacific White Shrimp (Litopenaeus vannamei) with Emphasis on Physiological Changes During Metamorphosis

The penaeid shrimp, with high commercial value, has a distinctive metamorphosis stage during early development. Although morphology study about this ontogeny has been developed for decades, genomic and transcriptomic information are still scarce. In this study, we have investigated the transcriptomic characteristics of the Pacific white shrimp (Litopenaeus vannamei) during five continuous developmental stages with high throughput Illumina/Solexa sequencing technology. We obtained 51,568,556, 52,824,674, 53,430,302, 53,902,786, 51,574,056 clean reads for embryo, nauplius, zoea, mysis, post-larva stages, respectively. The reads were assembled and clustered into 66,815unigenes, of which, 32,398have putative homologues in the non-redundant (nr) protein database from NCBI, 14,981 have been classified into diverse functional categories by Gene Ontology (GO) annotation and 26,257 have been associated with 255 pathways by KEGG pathway mapping.  Meanwhile,the differentially expressed genes(DEGs) between adjacent stages were identified and gene expression patterns were clustered. The results revealed that the maximum DEGs were identified between embryo and nauplius, indicating that most dramatic changes occurred in this period. We also made the GO enrichment and pathway enrichment analysis. DEGs between embryo and nauplius stages were significantly enriched in hormone induced programmed cell death process which related to histolysis and reconstruction; DEGs between nauplius and zoea stages were significantly enriched in digestive enzymes secretion and metabolic pathways, indicating that source of nutrition was transforming greatly in this period; DEGs between mysis and post-larva stages were significantly enriched in chitin metabolism and calcification process, which implied that calcified cuticle was generating abundantly in this transitional period. We believe these results will provide much support to better understand the physiological changes during metamorphosis especially histolysis, feeding transition, sex differentiation and cuticle formation. In conclusion, this is the first study that characterizes the integrated transcriptome patterns during early development of white shrimp, and these initial findings will serve assignificant reference for shrimp biology and functional gene research.

Jianhai XIANG^*  Correspondence and presenting author