Proteins Associated With Rice Stripe Virus Transmission In The Salivary Gland Of Laodelphax Striatellus

The small brown planthopper (SBPH) Laodelphax striatellus (Fallen) (Homoptera:Delphacidae) is one of the most important pest insects of rice in Asia. In addition to injuring rice plants Oryza sativa by sap-sucking via its piercing-sucking mouthparts, L. striatellus also acts as the most important vector of rice stripe virus (RSV), which causes rice stripe disease. RSV is a typical member of the genus Tenuivirus and is transmitted only in a persistent, circulative-propagative manner by L. striatellus. After being acquired, the virus viruses move through the insect vector, from the gut lumen into the hemolymph or other tissues and finally into the salivary glands from which these viruses are introduced back into the plant during insect feeding. Our previous study indicated that the expressions of some proteins, such as ATP synthase subunit alpha, tubulin alpha-2, NADP-dependent malic enzyme, mitochondrial import inner membrane translocase and ubiquitin-60S ribosomal protein L40 precursor in the salivary gland of viruliferous L. striatellus were significantly higher than those of naive vectors. The complete cDNA sequences and relative expressions of genes encoding NADP-dependent malic enzyme, mitochondrial import inner membrane translocase and ubiquitin-60S ribosomal protein L40 precursor were examined. The functions of genes encoding ATP synthase subunit alpha, tubulin alpha-2 and mitochondrial import inner membrane translocase in RSV transmission were investigated. The results were as follows.(1) The complete cDNA sequences genes encoding NADP-dependent malic enzyme, mitochondrial import inner membrane translocase and ubiquitin-60S ribosomal protein L40 precursor of viruliferous L. striatellus was obtained by reverse transcription polymerase chain reaction (RT-PCR) with rapid amplification of cDNA ends (RACE). The full-length sequences of NADP-dependent malic enzyme gene (Gene name:LsNADP), mitochondrial import inner membrane translocase (Gene name:LsMIT) and ubiquitin-60S ribosomal protein L40 precursor (Gene name:LsUBI) were 2060 bp,661bp and 1167 bp, respectively. The relative expressions of these three genes were significantly higher in viruliferous L. striatellus than those in naive vectors. In the salivary glands, the relative expressions of LsNADP, LsMIT and LsUBI increased by 17.4%,123.6% and 62.2%, respectively, compared to the control. In the vector body, the LsNADP, LsMIT and LsUBI were up-expressed increasing by 25.0%,43.4% and 16.7%, respectively, compared to the control.(2) RNAi silencing of LsATP, LsMIT and LsTUB genes were used to examine their functions in RSV transmission by viruliferous L. striatellus. The significance of RNA interference was obtained. The dsRNA decreased target gene expression by 63% for LsATP, by 82% for LsMIT, and by 76% for LsTUB, respectively, compared to controls. No obvious difference was observed in virus transmission rate by viruliferous L. striatellus treated with dsATP (dsMIT) compared to control, indicating that LsATP and LsTUB had less significance in RSV transmission. Virus inoculation rate of viruliferous L. striatellus treated with dsTUB was 12%, decreasing by 70% compared to the control. It indicated that LsTUB played an important role in RSV transmission. The underlying molecular mechanism of interaction between LsTUB and RSV needs further investigation.