Conotoxin Diversity in the Venom Gland Transcriptome of the Magician’s Cone, Pionoconus magus

Abstract

The transcriptomes of the venom glands of two individuals of the magician’s cone, Pionoconus magus, from Okinawa (Japan) were sequenced, assembled, and annotated. In addition, RNA-seq raw reads available at the SRA database from one additional specimen of P. magus from the Philippines were also assembled and annotated. The total numbers of identified conotoxin precursors and hormones per specimen were 118, 112, and 93. The three individuals shared only five identical sequences whereas the two specimens from Okinawa had 30 sequences in common. The total number of distinct conotoxin precursors and hormones for P. magus was 275, and were assigned to 53 conotoxin precursor and hormone superfamilies, two of which were new based on their divergent signal region. The superfamilies that had the highest number of precursors were M (42), O1 (34), T (27), A (18), O2 (17), and F (13), accounting for 55% of the total diversity. The D superfamily, previously thought to be exclusive of vermivorous cones was found in P. magus and contained a highly divergent mature region. Similarly, the A superfamily alpha 4/3 was found in P. magus despite the fact that it was previously postulated to be almost exclusive of the genus Rhombiconus. Differential expression analyses of P. magus compared to Chelyconus ermineus, the only fish-hunting cone from the Atlantic Ocean revealed that M and A2 superfamilies appeared to be more expressed in the former whereas the O2 superfamily was more expressed in the latter.

Comparative transcriptomics of the venoms of continental and insular radiations of West African cones

“…We considered as differentially expressed all those conotoxin precursor superfamilies with a PPDE greater than 0.95 and with a fold change above 32 (calculated as log 2 RealFC ≥ 5). The same type of analysis was performed to identify those superfamilies differentially expressed in the comparison between vermivory (using the 15 specimens of West Africa as replicates) and piscivory (using the three individuals of C. ermineus [8] and the three individuals of P. magus [29]). The Shapiro-Wilk test rejected the normality of the data, so a Kruskal-Wallis test was run in R [40] over those superfamilies identified as differentially expressed to confirm these results taking variance among replicates into consideration.…”

“…Here, we sequenced the venom gland transcriptomes from 13 species belonging to genera Africonus and Varioconus, as well as one from Kalloconus trochulus, which was used as outgroup. We aimed to (i) describe venom compositions in terms of the presence, member diversity and relative expression levels of the conotoxin precursor superfamilies; (ii) assess the levels of divergence in venom composition at different hierarchical (taxonomic) levels and discern between shared-derived peptides and potential cases of functional convergence; (iii) determine whether there could be instances of differential expression between the two genera as footprint of adaptation; and (iv) compare differential conotoxin expression between these vermivorous species and the piscivorous species Chelyconus ermineus [8] and Pionoconus magus [29] from the Atlantic and the Indo-Pacific oceans, respectively, to further understand the connections between venom evolution to diet specialization and defense.…”

A phylogeny-aware approach reveals unexpected venom components in divergent lineages of cone snails

“…A-, I2-, M-, O1-), and is reflected in diversified functions of the included gene families (see e.g. [37]).…”

“…When screening such clusters, the following conditions were checked: (i) predicted signal sequence lacking long repeats of one or two residues, such as ‘LLLLLLLLL’, ‘LSLSLSLSLSLS’ or ‘VSVSVSVSVSVSV’, (ii) complete precursor not exceeding 200 AA, (iii) mature region comprising over 20 AA, (iv) consistent alignment features within each SSC. Some identified clusters might, however, correspond to transcripts of house-keeping genes, including transcripts translated into the wrong frame [37]. To filter these out, we used BLASTx ( E -value 10–5) to search the nucleotide sequences of the SSCs against the SwissProt manually curated database [49].…”

Diversity of Conopeptides and Conoenzymes from the Venom Duct of the Marine Cone Snail Conus bayani as Determined from Transcriptomic and Proteomic Analyses

“…Initially, mass spectrometry analysis and Edman degradation methods were used to study the amino acid sequences of venom peptides [ 16 ]. Conotoxins undergo multiple types of modification after translation catalyzed by post-translation modifying enzymes [ 17 ]. Currently, transcriptomics has emerged as a valuable tool to characterize the diversity of peptides expressed by individual snails and has increased the pace of finding novel conotoxins in recent years [ 18 , 19 , 20 , 21 ].…”