| The small brown planthopper (SBPH) Laodelphax striatellus (Fallen) (Homoptera: Delphacidae) is one of the most destructive pest insects of rice in Asian. L. striatellus can transfer the Rice stripe virus (RSV) to host plants, which then develop rice stripe disease. RSV is the type member of the genus Tenuivirus, which relies on L. striatellus for its transmission in a persistent, circulative-propagative manner. Four types of barriers to persistent transmission of plant and animal viruses in their vectors have been proposed or identified:(i) midgut infection barrier, (ii) dissemination (including midgut escape and salivary gland infection) barriers, (iii) salivary gland escape barrier, and (iv) transovarial transmission barriers. The mechanism for salivary gland infection and escape in RSV remains unknown.Our previous resucts indicated that the expressions of some proteins, such as ATP synthase subunit alpha, mitochondrial import inner membrane translocase, NADP-dependent malic enzyme, tubulin alpha-2, ubiquitin-60S ribosomal protein L40 precursor and voltage-dependent anion-selective channel in the salivary gland of viruliferous L. striatellus were significantly higher than those of naive vectors. In this study, the complete cDNA sequences and relative expressions of genes encoding voltage-dependent anion-selective channel were examined. The effects of the genes encoding the above 6 proteins on the feeding behavior and RSV transmission were investigated. The results were as follows.(1) The complete cDNA sequences gene encoding voltage-dependent anion-selective channel was obtained by reverse transcription polymerase chain reaction (RT-PCR) with rapid amplification of cDNA ends (RACE). The full-length sequence of voltage-dependent anion-selective channel gene (Gene name:LsVDAC) was 1464 bp. The relative expression of LsVDAC was significantly higher in viruliferous L. striatellus than that in naive vectors. In the salivary gland, the relative expressions of LsVDAC increased by 49.2%. In the vector body, the LsVDAC was up-expressed increasing by 6.1%, compared to the control.(2) RNAi silencing of LsATP, LsMIT, LsNADP, LsTUB, LsUBI and LsVDAC genes were used to evaluate their effects on the feeding behavior and RSV transmission in viruliferous L. striatellus. The result indicated that the duration of water ingestion in xylem in L. striatellus treated with dsATP ((0.23±0.19) min) was significantly shorter than that the untreated control ((1.74±0.71) min). For L. striatellus treated with dsMIT, the duration of extracellular movement of stylet near the phloem region increased by 49.2%, compared to the untreated control. RAN silencing of gene LsNADP decreased the duration of water ingestion in xylem. RAN silencing of genes LsTUB and LsUBI did not affect the parameters of feeding behavior of treated vectors. For L. striatellus treated with dsVDAC, the duration of extracellular movement of stylet near the phloem region increased by 48.3%, and the duration of water ingestion in xylem significantly decreased, compared to the untreated control. No obvious difference was observed in virus transmission rate of viruliferous L. striatellus treated with dsATP, dsTUB and dsUBI compared to control, indicating that LsATP, LsTUB and dsUBI had less significance in RSV transmission. Virus inoculation rate of viruliferous L. striatellus treated with dsMIT, LsNADP and dsVDAC decreasing by 74.9%,87.6% and 74.9%, respectively, compared to the control.It indicated that dsMIT, LsNADP and dsVDAC played an important role in RSV transmission. Based on all the data obtained, we propose that the decrease of virus transmission rate of viruliferous L. striatellus treated with dsMIT, LsNADP and dsVDAC was not caused by the modified feeding behavior, but by the mediated energetic metabolism and the modified interaction between RSV and vector. |
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