Comparative analyses of the venom components in the salivary gland transcriptomes and saliva proteomes of some heteropteran insects

Abstract

Salivary gland‐specific transcriptomes of nine heteropteran insects with distinct feeding strategies (predaceous, hematophagous, and phytophagous) were analyzed and annotated to compare and identify the venom components as well as their expression profiles. The transcriptional abundance of venom genes was verified via quantitative real‐time PCR. Hierarchical clustering of 30 representative differentially expressed venom genes from the nine heteropteran species revealed unique groups of salivary gland‐specific genes depending on their feeding strategy. The commonly transcribed genes included a paralytic neurotoxin (arginine kinase), digestive enzymes (cathepsin and serine protease), an anti‐inflammatory protein (cystatin), hexamerin, and an odorant binding protein. Both predaceous and hematophagous (bed bug) heteropteran species showed relatively higher transcription levels of genes encoding proteins involved in proteolysis and cytolysis, whereas phytophagous heteropterans exhibited little or no expression of these genes, but had a high expression of vitellogenin, a multifunctional allergen. Saliva proteomes from four representative species were also analyzed. All venom proteins identified via saliva proteome analysis were annotated using salivary gland transcriptome data. The proteomic expression profiles of venom proteins were in good agreement with the salivary gland‐specific transcriptomic profiles. Our results indicate that profiling of the salivary gland transcriptome provides important information on the composition and evolutionary features of venoms depending on their feeding strategy.

You are what you eat—ecological niche and microhabitat influence venom activity and composition in aquatic bugs

“…We found many uncharacterized proteins in N. glauca venom, including several peptides with no known homologues, suggesting that prey immobilization by this species is facilitated by other proteins with distinct mechanisms of action. One protein family that was particularly abundant and strongly expressed in the venom glands of the three predatory species was heteropteran venom protein family 2, a group also present in other zoophagous and haematophagous bugs from various families but not in the phytophagous species investigated thus far [ 7 , 8 , 13 , 40 , 75 , 76 ]. The role of these proteins is unclear, but their strict gland-specific expression and abundance in predatory species suggest a key role in predation.…”

“…Previous studies have focused on terrestrial bugs and mainly investigated differences in the activity of digestive enzymes to draw conclusions about dietary habits [36][37][38][39]. Recently, the salivary protein composition was analysed in several terrestrial and two aquatic bugs from different suborders, revealing patterns that may indicate specific dietary habits [40]. The proteins characteristic of predatory bugs included CUB domain proteins, haemolysins, Ptu1-like peptides, redulysins and several uncharacterized peptides.…”

Proteinaceous Venom Expression of the Yellow Meadow Ant, Lasius flavus (Hymenoptera: Formicidae)

“…They are also expressed in non-chemosensory organs, such as pheromone glands, reproductive organs, and digestive tracts, but their potential functions remain largely uncharacterized [ 32 ]. Odorant binding protein has been found in the venom of several parasitoids, bees, and predatory bugs [ 33 , 34 , 35 , 36 , 37 , 38 ]. An odorant binding protein, AccOBP10, of the Chinese honey bee, Apis cerana cerana , with higher transcriptional levels in the venom gland than in other tissues, plays a role in the response to stress conditions [ 36 ].…”

An Assassin’s Secret: Multifunctional Cytotoxic Compounds in the Predation Venom of the Assassin Bug Psytalla horrida (Reduviidae, Hemiptera)

“…Although the venom composition of several assassin bug species has been analyzed recently [5,7,14], little is known about the compounds responsible for the observed effects. The most abundant peptides in assassin bug venoms include digestive enzymes, protease inhibitors, putative pore-forming proteins and neurotoxins, and a large number of uncharacterized proteins [1,5,7,12,14,15]. A recent study attempted to identify the insecticidal venom components of the red tiger assassin bug Havinthus rufovarius (Bergroth) by determining the toxic activity of venom fractions.…”

“…Moreover, trialysin/redulysin homologs are not only found in predacious true bugs but also in phytophagous species such as Riptortus pedestris (Fabricius), where they can act as antimicrobial agents [18]. A protein family that is also very abundant and highly expressed in the venom glands of many predatory bugs analyzed to date, is the heteropteran venom protein family 2 [5,7,14,15,19]. Similar to redulysins, family 2 proteins contain several conserved cysteine residues [19]; however, their function, activity, and role in the predacious lifestyle are still unknown.…”