The -tubulin ofLaodelphax striatellusmediates the passage of rice stripe virus (RSV) and enhances horizontal transmission

Author summary Over 70% of all known plant viruses are transmitted by specific arthropods, mainly including planthoppers, leafhoppers, aphids and whiteflies. Plant viruses with persistent relationships must overcome multiple barriers. Among these barriers, midgut and salivary glands are first and last barriers to the viral transmission. The interactions of host factors and virus in the insect midguts and salivary glands provide critical information regarding viral spread in the insect vector and subsequent infection of host plants. However, the precise mechanisms is still lacking. Here, we found that the specific interaction between a alpha-tubulin 2 ofLaodelphax striatellus(SBPH) (LsTUB) and a nonstructural protein 3 (NS3)Rice stripe virus(RSV) mediates the passage of RSV through midgut and salivary glands, thereby leading to successful horizontal transmission. Our results confirm novel functions of LsTUB and NS3 in RSV transmission in insect vector. LsTUB may be a promising target for blocking horizontal transmission of RSV. These insights provide a better understanding of the interaction between plant viruses and vectors and may develop novel methods to control the systemic spread of plant viruses. Rice stripe virus(RSV, genusTenuivirus, familyPhenuiviridae) is the causal agent of rice stripe disease transmitted by the small brown planthopper (SBPH,Laodelphax striatellus) in a persistent propagative manner. The midgut and salivary glands of SBPH are the first and last barriers to the viral circulation and transmission processes, respectively; however, the precise mechanisms used by RSV to cross these organs and transmit to rice plants have not been fully elucidated. We obtained the full-length cDNA sequence ofL.striatellus alpha-tubulin 2(LsTUB) and found that RSV infection increased the level of LsTUBin vivo. Furthermore, LsTUB was shown to co-localize with RSV nonstructural protein 3 (NS3)in vivoand bound NS3 at positions 74-76 and 80-82in vitro. Transient gene silencing ofLsTUBexpression caused a significant reduction in detectable RSV loads and viralNS3expression levels, but had no effect on NS3 silencing suppressor activity and viral replication in insect cells. However, suppression of LsTUB attenuated viral spread in the bodies of SBPHs and decreased RSV transmission rates to rice plants. Electrical penetration graphs (EPG) showed that LsTUB knockdown by RNAi did not impact SBPH feeding; therefore, the reduction in RSV transmission rates was likely caused by a decrease in viral loads inside the planthopper. These findings suggest that LsTUB mediates the passage of RSV through midgut and salivary glands and leads to successful horizontal transmission.