Abstract
Exoskeleton construction is an important issue in shrimp. To better understand the molecular mechanism of exoskeleton formation, development and reconstruction, the transcriptome of the entire developmental process in Litopenaeus vannamei, including nine early developmental stages and eight adult-moulting stages, was sequenced and analysed using Illumina RNA-seq technology. A total of 117,539 unigenes were obtained, with 41.2% unigenes predicting the full-length coding sequence. Gene Ontology, Clusters of Orthologous Group (COG), the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and functional annotation of all unigenes gave a better understanding of the exoskeleton developmental process in L. vannamei. As a result, more than six hundred unigenes related to exoskeleton development were identified both in the early developmental stages and adult-moulting. A cascade of sequential expression events of exoskeleton-related genes were summarized, including exoskeleton formation, regulation, synthesis, degradation, mineral absorption/reabsorption, calcification and hardening. This new insight on major transcriptional events provide a deep understanding for exoskeleton formation and reconstruction in L. vannamei. In conclusion, this is the first study that characterized the integrated transcriptomic profiles cover the entire exoskeleton development from zygote to adult-moulting in a crustacean, and these findings will serve as significant references for exoskeleton developmental biology and aquaculture research.
Highlights
As the largest phylum of animals with over a million described species, arthropods make up more than 80% of all known living animal species all over the world[1]
The products extracted from the exoskeleton, such as chitin, chitosan and chitosan oligosaccharides have been widely used in the fields of chemical industry and medicine[15, 16]
Based on the functional gene profiling analysis, we summarized the genes related to exoskeleton formation, development and reconstruction from the following perspectives, including: (i) Cuticle protein, (ii) Moulting-hormone, (iii) Exoskeleton degradation, (iv) Mineral absorption, (v) Mineral reabsorption, (vi) Exoskeleton synthesis, (vii) Ion channel, (viii) Moulting signaling pathway and (ix) Late gene of moulting
Summary
As the largest phylum of animals with over a million described species, arthropods make up more than 80% of all known living animal species all over the world[1]. The exoskeleton provides an arthropods shape, water-proofing, locomotion, and can be very important for growth, development and reproduction[3]. This structure confines metamorphosis, body growth and mating. Litopenaeus vannamei, one of the most important economic species of decapoda, is the most commonly cultured shrimp species in the world. It is an ideal model for analysing the exoskeleton development. The exoskeleton of shrimp is composed of the polysaccharide chitin, cuticle proteins and mineral deposits It is a four-layered matrix including an epicuticle, exocuticle, endocuticle and epidermis[20].
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