Venom gland transcriptomes of two elapid snakes (Bungarus multicinctus and Naja atra) and evolution of toxin genes

Abstract

BackgroundKraits (genus Bungarus) and cobras (genus Naja) are two representative toxic genera of elapids in the old world. Although they are closely related genera and both of their venoms are very toxic, the compositions of their venoms are very different. To unveil their detailed venoms and their evolutionary patterns, we constructed venom gland cDNA libraries and genomic bacterial artificial chromosome (BAC) libraries for Bungarus multicinctus and Naja atra, respectively. We sequenced about 1500 cDNA clones for each of the venom cDNA libraries and screened BAC libraries of the two snakes by blot analysis using four kinds of toxin probes; i.e., three-finger toxin (3FTx), phospholipase A2 (PLA2), kunitz-type protease inhibitor (Kunitz), and natriuretic peptide (NP).ResultsIn total, 1092 valid expressed sequences tags (ESTs) for B. multicinctus and 1166 ESTs for N. atra were generated. About 70% of these ESTs can be annotated as snake toxin transcripts. 3FTx (64.5%) and β bungarotoxin (25.1%) comprise the main toxin classes in B. multicinctus, while 3FTx (95.8%) is the dominant toxin in N. atra. We also observed several less abundant venom families in B. multicinctus and N. atra, such as PLA2, C-type lectins, and Kunitz. Peculiarly a cluster of NP precursors with tandem NPs was detected in B. multicinctus. A total of 71 positive toxin BAC clones in B. multicinctus and N. atra were identified using four kinds of toxin probes (3FTx, PLA2, Kunitz, and NP), among which 39 3FTx-postive BACs were sequenced to reveal gene structures of 3FTx toxin genes.ConclusionsBased on the toxin ESTs and 3FTx gene sequences, the major components of B. multicinctus venom transcriptome are neurotoxins, including long chain alpha neurotoxins (α-ntx) and the recently originated β bungarotoxin, whereas the N. atra venom transcriptome mainly contains 3FTxs with cytotoxicity and neurotoxicity (short chain α-ntx). The data also revealed that tandem duplications contributed the most to the expansion of toxin multigene families. Analysis of nonsynonymous to synonymous nucleotide substitution rate ratios (dN/dS) indicates that not only multigene toxin families but also other less abundant toxins might have been under rapid diversifying evolution.

De novo transcriptome analysis of rose-scented geranium provides insights into the metabolic specificity of terpene and tartaric acid biosynthesis

“…In total, 6040 SSR motifs (mono to hexa nucleotides) were identified in 5380 contigs (Additional file 11), which corresponds to 6.8% of the total unique transcripts. The result agrees with previous studies reporting approximately 3–7% of expressed sequences with putative SSR motifs [54]. Out of these analyzed transcripts, 571 contained more than one SSR, whereas, 316 were in compound form (Table 2).…”

Production and Characterization of Neutralizing Antibodies against Bungarus multicinctus Snake Venom

“…The Bungarus multicinctus snake of the Elapidae family, which is also called the banded krait, is one of the major causes of snake envenomation in Taiwan. Neurotoxic venom proteins from B. multicinctus contain different toxins, enzymes, and components that damage the central nervous system and cause neuromuscular blockage, which results in different symptoms, such as ptosis and especially paralysis of the respiratory muscles leading to death (2,3). Among these components, bungarotoxins, which belong to a three-finger toxin family, are considered the major lethal components in B. multicinctus proteins.…”

Cobra venom proteome and glycome determined from individual snakes of Naja atra reveal medically important dynamic range and systematic geographic variation

“…The three-dimensional structures of most toxic components, including NTXs [9], PLA2s [10], CTXs (with different homologues of A1, A2, A3, A4, A5 and A6) [11], snake venom metalloproteinase (SVMP; K-like and atragin) [12], cysteine-rich secretory protein (CRISP) [13], and venom nerve growth factor (vNGF) [14] from Naja atra, are available. In addition, the genome from the king cobra (Ophiophagus hannah) [15], transcriptome from N. atra [16], and proteomes from African (Naja mossambica, Naja nigricollis, Naja katiensis, Naja nubiae, Naja pallida, and Naja haje) [17] and southeast Asian cobras (Naja kaouthia and Naja sumatrana) [7,18] have also been reported recently. Results of these studies indicate that postgenomic mechanisms may account for medically important variations in snake venom compositions [15][16][17][18][19].…”

“…In addition, the genome from the king cobra (Ophiophagus hannah) [15], transcriptome from N. atra [16], and proteomes from African (Naja mossambica, Naja nigricollis, Naja katiensis, Naja nubiae, Naja pallida, and Naja haje) [17] and southeast Asian cobras (Naja kaouthia and Naja sumatrana) [7,18] have also been reported recently. Results of these studies indicate that postgenomic mechanisms may account for medically important variations in snake venom compositions [15][16][17][18][19].…”

“…Based on the reported venomic profiles of most cobras (7,8,17,18) and the accumulated 2D and 3D structural databases in the last three decades for the cobra venom proteins from N. atra alone (see Introduction), the identifiable 21 protein components reported in this study are estimated to cover about 95% weight percentage of the entire N. atra venomic profile. For a clear identification of other minor toxin components such as Vespryn (Oharin), Cystatin, C-type lectins, Kunitz, phosphodiesterase and several other orphan toxins reported in the transcriptome profile of N. atra (16) would require similar analysis armed with additional N-terminal sequencing on larger amount (~2-3 mg) of samples.…”