Alternative Transcription at Venom Genes and Its Role as a Complementary Mechanism for the Generation of Venom Complexity in the Common House Spider

Abstract

The complex composition of venom, a proteinaceous secretion used by diverse animal groups for predation or defense, is typically viewed as being driven by gene duplication in conjunction with positive selection, leading to large families of diversified toxins with selective venom gland expression. Yet, the production of alternative transcripts at venom genes is often overlooked as another potentially important process that could contribute proteins to venom, and requires comprehensive datasets integrating genome and transcriptome sequences together with proteomic characterization of venom to be fully documented. In the common house spider, Parasteatoda tepidariorum , we used RNA sequencing of four tissue types in conjunction with the sequenced genome to provide a comprehensive transcriptome annotation. We also used mass spectrometry to identify a minimum of 99 distinct proteins in P tepidariorum venom, including at least 33 latrotoxins, pore-forming neurotoxins shared with the confamilial black widow. We found that venom proteins are much more likely to come from multiple transcript genes, whose transcripts produced distinct protein sequences. The presence of multiple distinct proteins in venom from transcripts at individual genes was confirmed for eight loci by mass spectrometry, and is possible at 21 others. Alternative transcripts from the same gene, whether encoding or not encoding a protein found in venom, showed a range of expression patterns, but were not necessarily restricted to the venom gland. However, approximately half of venom protein encoding transcripts were found among the 1,318 transcripts with strongly venom gland biased expression. Our findings revealed an important role for alternative transcription in generating venom protein complexity and expanded the traditional model of venom evolution.

Spider Venom: Components, Modes of Action, and Novel Strategies in Transcriptomic and Proteomic Analyses

“…Interestingly, a similar case has been recently described in a study comparing the transcriptomes of venom glands, silk glands, ovaries, and the prosoma without the venom glands of Parasteatoda tepidariorum ([23] STable6). The authors reported that “in contrast with the selective expression in the venom gland as posited in the traditional model of venom evolution …, many of the individual transcripts that produce venom proteins in this study have some level of expression in other tissues (silk, ovary, or cephalothorax).” [23]. The exact sequencing conditions including multiplexing level and samples multiplexed are not disclosed.…”

“…After a long period dominated by Edman degradation, new DNA sequencing techniques and soft ionization techniques for mass spectrometry (matrix-assisted laser desorption/ionization (MALDI), and electrospray ionization (ESI)) accelerated also spider venom research. Meanwhile, dozens of venom gland cDNA libraries, sequenced by Sanger, Roche 454 and Illumina techniques [16,17,18,19,20,21,22,23,24] diversified our knowledge on spider venom within less than two decades considerably. Here we review the state of the art of the composition of spider venoms and the currently available methods to analyze it.…”

Development of high-throughput screening assays for profiling snake venom Phospholipase A2activity after high-resolution chromatographic fractionation

“…Daboia russelii russelii (DRR) snake venom, which is known for its relatively high content of svPLA 2 , was used as a test venom for assay optimization at a concentration of 12.5 µg/mL. [11] Figure 1 shows time-course absorbance measurements in a cuvette using optimized assay conditions and DRR venom.…”

“…Venom composition is typically complex (50-200 proteins per species) and highly variable, with often extensive inter-specific, and even, intra-specific venom variations observed. [11,12] Rooted in the latter are geographical differences, living habitat, sex, and age of a snake, thereby increasing venom complexity even more. [13,14] Consequently, antivenom therapies, which are based on antibodies produced in horses or sheep following their immunization with venom or mixtures of venoms, are highly specific to those venoms used for production, but often lack efficacy for treating snakebites by other snake species.…”

Development of high-throughput screening assays for profiling snake venom phospholipase A2 activity after chromatographic fractionation

“…These venoms comprise many different pathological proteins and peptides, and other organic molecules. Venom composition is typically complex (50-200 proteins per species) and highly variable, with often extensive interspecific, and even, intra-specific venom variations observed (Casewell et al, 2014;Haney et al, 2019). Rooted in the latter are geographical differences, living habitat, sex, and age of a snake, thereby increasing venom complexity even more (Calvete, 2019;Gopalakrishnakone and Calvete, 2016).…”