Characterization of Rice Black-Streaked Dwarf Virus- and Rice Stripe Virus-Derived siRNAs in Singly and Doubly Infected Insect Vector Laodelphax striatellus

Yongqiang Ji,Jiangfeng Shen,Yuanda Lv,Ida Bagus Andika,Jianping Chen,Jianming Qiu,Liying Sun,Junmin Li

doi:10.1371/journal.pone.0066007

Abstract

Replication of RNA viruses in insect cells triggers an antiviral defense that is mediated by RNA interference (RNAi) which generates viral-derived small interfering RNAs (siRNAs). However, it is not known whether an antiviral RNAi response is also induced in insects by reoviruses, whose double-stranded RNA genome replication is thought to occur within core particles. Deep sequencing of small RNAs showed that when the small brown planthopper (Laodelphax striatellus) was infected by Rice black-streaked dwarf virus (RBSDV) (Reoviridae; Fijivirus), more viral-derived siRNAs accumulated than when the vector insect was infected by Rice stripe virus (RSV), a negative single-stranded RNA virus. RBSDV siRNAs were predominantly 21 and 22 nucleotides long and there were almost equal numbers of positive and negative sense. RBSDV siRNAs were frequently generated from hotspots in the 5′- and 3′-terminal regions of viral genome segments but these hotspots were not associated with any predicted RNA secondary structures. Under laboratory condition, L. striatellus can be infected simultaneously with RBSDV and RSV. Double infection enhanced the accumulation of particular genome segments but not viral coat protein of RBSDV and correlated with an increase in the abundance of siRNAs derived from RBSDV. The results of this study suggest that reovirus replication in its insect vector potentially induces an RNAi-mediated antiviral response.

Highlights

The small brown planthopper (Laodelphax striatellus; family Delphacidae, order Hemiptera) is one of the most economically important insects and is found world-wide, mainly in temperate regions [1]
Of 419 insects analyzed, 160 were infected with Rice stripe virus (RSV) (SI_RSV) (SI; singly infected), 98 were infected with Rice black-streaked dwarf virus (RBSDV) (SI_RB), 81 were doubly-infected (DI) and 80 were virus free (VF) (Fig. 1B). This result demonstrates that L. striatellus can carry RSV and RBSDV simultaneously
Because vsiRNAs are the key mediators of the antiviral RNA interference (RNAi) response, their identification and characterization provides important clues for the understanding of antiviral responses

Summary

Introduction

The small brown planthopper (Laodelphax striatellus; family Delphacidae, order Hemiptera) is one of the most economically important insects and is found world-wide, mainly in temperate regions [1]. The agricultural importance of L. striatellus is mainly because it is an efficient vector of two economically important rice viruses: Rice black-streaked dwarf virus (RBSDV) and Rice stripe virus (RSV) in a persistent propagative manner [2,3]. RBSDV and RSV move from the insect gut into the hemolymph or other organs and enter the salivary glands [4]. Both viruses can replicate in the different organs of the planthopper and are transmitted to plants during feeding [2,3,4]. RSV is the type member of genus Tenuivirus and its genome consists of 4 single stranded RNA segments. Co-infection of rice by RSV and RBSDV has been observed in the field [7], but it has not been shown whether the two viruses can be present simultaneously within the same insect vector in nature

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