Comparative transcriptomic analysis of salivary glands between the zoophytophagous Cyrtorhinus lividipennis and the phytozoophagous Apolygus lucorum.

BACKGROUND: Saliva plays a crucial role in shaping the feeding behavior of insects, involving processes such as food digestion and the regulation of interactions between insects and their hosts. Cyrtorhinus lividipennis serves as a predominant natural enemy of rice pests, while Apolygus lucorum, exhibiting phytozoophagous feeding behavior, is a destructive agricultural pest. In this study, a comparative transcriptome analysis, incorporating the published genomes of C.lividipennis and A.lucorum, was conducted to reveal the role of salivary secretion in host adaptation. RESULTS: In contrast to A.lucorum, C.lividipennis is a zoophytophagous insect. A de novo genome analysis of C.lividipennis yielded 19,706 unigenes, including 16,217 annotated ones. On the other hand, A.lucorum had altogether 20,111 annotated genes, as obtained from the published official gene set (20,353 unigenes). Functional analysis of the top 1,000 salivary gland (SG)-abundant genes in both insects revealed that the SG was a dynamically active tissue engaged in protein synthesis and secretion. Predictions of other tissues and signal peptides were compared. As a result, 94 and 157 salivary proteins were identified in C.lividipennis and A.lucorum, respectively, and were categorized into 68 and 81 orthogroups. Among them, 26 orthogroups were shared, potentially playing common roles in digestion and detoxification, including several venom serine proteases. Furthermore, 42 and 55 orthogroups were exclusive in C.lividipennis and A.lucorum, respectively, which were exemplified by a hyaluronidase in C.lividipennis that was associated with predation, while polygalacturonases in A.lucorum were involved in mesophyll-feeding patterns. CONCLUSIONS: Findings in this study provide a comprehensive insight into saliva secretions in C.lividipennis and A.lucorum via a transcriptome approach, reflecting the intricate connections between saliva secretions and feeding behaviors. It is found that conserved salivary secretions are involved in shaping the overlapping feeding patterns, while a plethora of unique salivary secretions may drive the evolution of specific feeding behaviors crucial for their survival. These results enhance our understanding of the feeding mechanisms in different insects from the perspective of saliva and contribute to future environmentally friendly pest control by utilizing predatory insects.

Complete genome analysis of a novel narnavirus in sweet viburnum (Viburnum odoratissimum).

Trees and shrubs provide important ecological services. However, few studies have surveyed the virome in trees and shrubs. In this study, we discovered a new positive-sense RNA virus originating from Viburnum odoratissimum, which we named "Vo narna-like virus". The complete genome of Vo narna-like virus is 3,451 nt in length with an open reading frame (ORF) encoding the RNA-dependent RNA polymerase (RdRP) protein. Phylogenetic analysis placed this virus within the betanarnavirus clade, sharing 53.63% amino acid sequence identity with its closest relative, Qingdao RNA virus 2. The complete sequence of the virus was confirmed by rapid amplification of cDNA ends (RACE) and Sanger sequencing. Small interfering RNA (siRNA) analysis indicated that this virus interacts with the RNA interference (RNAi) pathway of V. odoratissimum. This is the first report of a narnavirus in V. odoratissimum.