Transcriptome analysis of small brown planthopper, Laodelphax striatellus carrying Rice Stripe Virus

Abstract

Rice stripe virus (RSV), the type member of the genus Tenuivirus which causes rice stripe disease, transmits by the feeding behavior of small brown planthopper (SBPH), Laodelphax striatellus. Because RSV replicates in SBPH persistently and SBPH has sap-sucking feeding behavior with its piercing-sucking mouthpart in the phloem, SBPH is one of the most notorious vectors of RSV. So far, most considerations have been focused on the protection of the rice from RSV and/or the SBPH rather than the interactions among the rice, RSV and SBPH. Hence, to investigate the interactions between the virus and vector insect, total RNA was extracted from RSV-viruliferous SBPH (RVLS) and non-viruliferous SBPH (NVLS) adults to construct expressed sequence tag databases for comparative transcriptome analysis. Over 30 million bases were sequenced by 454 pyrosequencing to construct 1,538 and 953 of isotigs of SBPH from the mRNA of RVLS and NVLS, respectively. The gene ontology (GO) analysis demonstrated that both transcriptomes of RVLS and NVLS have similar GO structure, however, the gene expression pattern analysis revealed that 108 genes were up-regulated and 28 genes were down-regulated significantly in the RVLS. These RSV-dependently regulated genes of SBPH possibly have important roles in the physiology and behavior of SBPH, transmission of RSV, and RSV and SBPH interaction. Also, two kinds of picorna-like viruses were newly discovered from the EST libraries of each NVLS and RVLS, Which were named LsPV-1 and LsPV-2, respectively. The sequence analysis result revealed that LsPV-1 was a Korean isolate of Himetobi-P virus (HiPV) which belongs to dicistorovidae while the LsPV-2 genome structure resembled that of iflaviridae. A phylogenetic analysis of LsPV-2 RNA dependent RNA polymerase sequence showed that honeybee deformed wing virus was the most closely related virus. Interestingly, RSV and HiPV seem not to superinfect SBPH which already carrying the other virus, therefore, the incompatibility between RSV and HiPV might give us a clue to understand the viral microflora and the mechanism of persistency in SBPH. Also, The HiPV and LsPV-2 were incompatible each other in SBPH, suggesting that theses tow picorna-like viruses may have important functions in transmission of the RSV.