Transcriptome response comparison between vector and non-vector aphids after feeding on virus-infected wheat plants.

BACKGROUND: Plant viruses maintain intricate interactions with their vector and non-vector insects and can impact the fitness of insects. However, the details of their molecular and cellular mechanisms have not been studied well. We compared the transcriptome-level responses in vector and non-vector aphids (Schizaphis graminum and Rhopalosiphum padi, respectively) after feeding on wheat plants with viral infections (Barley Yellow Dwarf Virus (BYDV) and Wheat dwarf virus (WDV), respectively). We conducted differentially expressed gene (DEG) annotation analyses and observed DEGs related to immune pathway, growth, development, and reproduction. And we conducted cloning and bioinformatic analyses of the key DEG involved in immune. RESULTS: For all differentially expressed gene analyses, the numbers of DEGs related to immune, growth, development, reproduction and cuticle were higher in vector aphids than in non-vector aphids. STAT5B (signal transducer and activator of transcription 5B), which is involved in the JAK-STAT pathway, was upregulated in R. padi exposed to WDV. The cloning and bioinformatic results indicated that the RpSTAT5B sequence contains a 2082 bp ORF encoding 693 amino acids. The protein molecular weight is 79.1 kD and pI is 8.13. Analysis indicated that RpSTAT5B is a non-transmembrane protein and a non-secreted protein. Homology and evolutionary analysis indicated that RpSTAT5B was closely related to R. maidis. CONCLUSIONS: Unigene expression analysis showed that the total number of differentially expressed genes (DEGs) in the vector aphids was higher than that in the non-vector aphids. Functional enrichment analysis showed that the DEGs related to immunity, growth and reproduction in vector aphids were higher than those in non-vector aphids, and the differentially expressed genes related to immune were up-regulated. This study provides a basis for the evaluation of the response mechanisms of vector/non-vector insects to plant viruses.

Virus-Dependent and -Independent Responses of Sitobion avenae (Homoptera: Aphididae) Feeding on Wheat Infected by Transmitted and Nontransmitted Viruses at Transcriptomic Level.

Most plant viruses maintain complex interactions with their vector or nonvector insects and can indirectly (via host plants) or directly affect the fitness of insects. However, little is known about the genes involved in the interactions between insects and transmitted or nontransmitted viruses, particularly nontransmitted viruses. Sitobion avenae (Fabricius) is a vector of barley yellow dwarf virus GAV strains (BYDV-GAV), but not a vector of wheat dwarf virus (WDV), which is transmitted by the leafhopper [Psammotettix alienus (Dahlbom)]. In this study, S. avenae was utilized to determine the transcriptomic responses after feeding on wheat infected by each of the two viruses, respectively, using an Illumina Hiseq sequencing platform. The transcriptomic data presented 61,508 genes, of which 854 differentially expressed. Moreover, in addition to sharing 208 genes, the number of differentially expressed genes (DEGs) in S. avenae exposed to BYDV was higher (800) than that when exposed to WDV (262). The DEGs related to the immune system and fitness of S. avenae in response to BYDV-/WDV-infected plants were identified and analyzed using Gene Ontologies (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG), and the number of related DEGs was lower as nonvector than as vector. This study provides the baseline information to further examine molecular mechanisms of how wheat viruses affect S. avenae fitness and immune response either as a vector for BYDV-GAV or as a nonvector for WDV.