Abstract
Anisakis pegreffii is known as one of the causes of a fish-borne zoonosis, anisakidosis. Despite its significant public health and food hygiene impacts, little is known of the pathogenesis, genetic background of this parasite, at least partly due to the lack of genome and transcriptome information. In this study, RNA-seq and de novo assembly were conducted to obtain transcriptome profiles of the A. pegreffii third and fourth larvae. The third stage larvae (APL3) were collected from chub mackerel and the fourth stage larvae (APL4) were obtained by in vitro culture. In total, 47,243 and 43,660 unigenes were expressed in APL3 and APL4 transcriptomes. Of them, 18,753 were known and 28,490 were novel for APL3, while 18,996 were known and 24,664 were novel for APL4. The most abundantly expressed genes in APL3 were mitochondrial enzymes (COI, COII, COIII) and polyubiquitins (UBB, UBIQP_XENLA). Collagen-related genes (col-145, col-34, col-138, Bm1_54705, col-40) were the most abundantly expressed in APL4. Mitochondrial enzyme genes (COIII, COI) were also highly expressed in APL4. Among the transcripts, 614 were up-regulated in APL3, while 1,309 were up-regulated in APL4. Several protease and protein biosynthesis-related genes were highly expressed in APL3, all of which are thought to be crucial for invading host tissues. Collagen synthesis-related genes were highly expressed in APL4, reflecting active biosynthesis of collagens occurs during moulting process of APL4. Of these differentially expressed genes, several genes (SI, nas-13, EF-TSMT, SFXN2, dhs-27) were validated to highly transcribed in APL3, while other genes (col-40, F09E10.7, pept-1, col-34, VIT) in APL4. The biological roles of these genes in vivo will be deciphered when the reference genome sequences are available, together with in vitro experiments.
Highlights
The family Anisakidae comprises the nematode species whose adult stages can be found in aquatic animals, while the third stage larvae (L3) generally exist in the body cavity, visceral organs and muscles of various fish and squid species
Since molecular approaches have been introduced for identification of anisakid nematodes, it was proved that there are three species in A. simplex complex and of them, the two sibling species A. simplex sensu stricto (s.s.) and A. pegreffii were shown to be the causative agent of human infection (Mattiucci and D’Amelio, 2014 and the references therein)
47, 243 and 43,660 genes were expressed in A. pegreffii L3 (APL3) and APL4, respectively (> fpkm 1.0)
Summary
The family Anisakidae comprises the nematode species whose adult stages can be found in aquatic animals, while the third stage larvae (L3) generally exist in the body cavity, visceral organs and muscles of various fish and squid species. Humans are not the final hosts of these nematodes, the larval forms of anisakid nematodes, those of the genera Anisakis and Pseudoterranova are known to be associated with human infection by the ingestion of raw or undercooked fish or cephalopods harboring these larvae (Mattiucci and D’Amelio, 2014). Infection with these nematodes is considered to be a Commons CC BY 4.0 license, https://creativecommons.org/licenses/by/4.0/. We compared transcriptomes of these two different stages of A. pegreffii to provide detailed information on differences regarding their biology and pathogenicity against their hosts
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