Reference gene and tropomyosin expression in mud crab Scylla olivacea, Scylla paramamosain and Scylla tranquebarica

Variation in Shrimp Allergens: Place of Origin Effects on Food Safety Assessment

Due to the widespread use of shellfish ingredients in food products, accurate food labelling is urgently needed for consumers with shellfish allergies. Most crustacean allergen detection systems target the immunorecognition of the allergenic protein tropomyosin. However, this mode of detection may be affected by an origin-dependent protein composition. This study determined if the geographic location of capture, or aquaculture, influenced the allergenic protein profiles of Black Tiger Shrimp (Penaeus monodon), one of the most farmed and consumed shrimp species worldwide. Protein composition was analysed in shrimp from nine different locations in the Asia-Pacific by SDS-PAGE, immunoblotting, and mass spectrometry. Ten of the twelve known shrimp allergens were detected, but with considerable differences between locations. Sarcoplasmic calcium-binding protein, myosin light chain, and tropomyosin were the most abundant allergens in all locations. Hemocyanin-specific antibodies could identify up to six different isoforms, depending on the location of origin. Similarly, tropomyosin abundance varied by up to 13 times between locations. These findings suggest that allergen abundance may be related to shrimp origin and, thus, shrimp origin might directly impact the readout of commercial crustacean allergen detection kits, most of which target tropomyosin, and this should be considered in food safety assessments.

A novel Dmrt gene of crustacean: functional analysis of idmrt-2 gene in the male reproductive system from Scylla paramamosain

The Dmrt (double-sex and mab-3 related transcription factor) gene family is considered to be a highly conserved gene family related to sex determination and sexual differentiation across species. In order to better understand the role of the idmrt-2 gene in gonad development in Scylla paramamosain, the idmrt-2 gene was cloned and analyzed. The cDNA contains a 1659 bp ORF region encoding 552 amino acids. The qRT-PCR results showed that idmrt-2 was significantly more expressed in the testis than in other tissues (p<0.05). The expression of idmrt-2 was highest in the spermatids stage (T2 stage), followed by the mature sperms stage (T3 stage) and significantly higher than in the spermatocytes stage (T1 stage) (p<0.05) during testicular development and the expression difference was not significant in different stages of ovarian development. RNAi studies revealed that after idmrt-2 was knocked down, the expression of Dmrt-like and foxl-2 genes in the testis decreased, as well as IAG expression in the androgenic gland. The findings suggest that idmrt-2 may be an IAG regulator and involved in testicular development.

Molecular and allergenic characterization of recombinant tropomyosin from mud crab Scylla olivacea

BACKGROUND

Tropomyosin is a major allergen in crustaceans, including mud crab species, but its molecular and allergenic properties in Scylla olivacea are not well known. Thus, this study aimed to produce the recombinant tropomyosin protein from S. olivacea and subsequently investigate its IgE reactivity.

METHODS AND RESULTS

The tropomyosin gene was cloned and expressed in the Escherichia coli system, followed by SDS-PAGE and immunoblotting test to identify the allergenic potential of the recombinant protein. The 855-base pair of tropomyosin gene produced was found to be 99.18% homologous to Scylla serrata. Its 284 amino acids matched the tropomyosin of crustaceans, arachnids, insects, and Klebsiella pneumoniae, ranging from 79.03 to 95.77%. The tropomyosin contained 89.44% alpha-helix folding with a tertiary structure of two-chain alpha-helical coiled-coil structures comprising a homodimer heptad chain. IPTG-induced histidine tagged-recombinant tropomyosin was purified at the size of 42 kDa and confirmed as tropomyosin using anti-tropomyosin monoclonal antibodies. The IgE binding of recombinant tropomyosin protein was reactive in 90.9% (20/22) of the sera from crab-allergic patients.

CONCLUSIONS

This study has successfully produced an allergenic recombinant tropomyosin from S. olivacea. This recombinant tropomyosin may be used as a specific allergen for the diagnosis of allergy.