Massively parallel pyrosequencing-based transcriptome analyses of small brown planthopper (Laodelphax striatellus), a vector insect transmitting rice stripe virus (RSV)

Fujie Zhang,Huajun Zheng,Xiaoying Chen,Rongxiang Fang,Shengyue Wang,Yijun Zhou,Hongyan Guo,Wei Qian,Tong Zhou

doi:10.1186/1471-2164-11-303

Abstract

BackgroundThe small brown planthopper (Laodelphax striatellus) is an important agricultural pest that not only damages rice plants by sap-sucking, but also acts as a vector that transmits rice stripe virus (RSV), which can cause even more serious yield loss. Despite being a model organism for studying entomology, population biology, plant protection, molecular interactions among plants, viruses and insects, only a few genomic sequences are available for this species. To investigate its transcriptome and determine the differences between viruliferous and naïve L. striatellus, we employed 454-FLX high-throughput pyrosequencing to generate EST databases of this insect.ResultsWe obtained 201,281 and 218,681 high-quality reads from viruliferous and naïve L. striatellus, respectively, with an average read length as 230 bp. These reads were assembled into contigs and two EST databases were generated. When all reads were combined, 16,885 contigs and 24,607 singletons (a total of 41,492 unigenes) were obtained, which represents a transcriptome of the insect. BlastX search against the NCBI-NR database revealed that only 6,873 (16.6%) of these unigenes have significant matches. Comparison of the distribution of GO classification among viruliferous, naïve, and combined EST databases indicated that these libraries are broadly representative of the L. striatellus transcriptomes. Functionally diverse transcripts from RSV, endosymbiotic bacteria Wolbachia and yeast-like symbiotes were identified, which reflects the possible lifestyles of these microbial symbionts that live in the cells of the host insect. Comparative genomic analysis revealed that L. striatellus encodes similar innate immunity regulatory systems as other insects, such as RNA interference, JAK/STAT and partial Imd cascades, which might be involved in defense against viral infection. In addition, we determined the differences in gene expression between vector and naïve samples, which generated a list of candidate genes that are potentially involved in the symbiosis of L. striatellus and RSV.ConclusionsTo our knowledge, the present study is the first description of a genomic project for L. striatellus. The identification of transcripts from RSV, Wolbachia, yeast-like symbiotes and genes abundantly expressed in viruliferous insect, provided a starting-point for investigating the molecular basis of symbiosis among these organisms.

Highlights

The small brown planthopper (Laodelphax striatellus) is an important agricultural pest that damages rice plants by sap-sucking, and acts as a vector that transmits rice stripe virus (RSV), which can cause even more serious yield loss
Using the above-mentioned proteins of D. melanogaster as search queries, we found that L. striatellus encodes homologs of Janus kinase (JAK), Domeless, and signal transduction and activators of transcription (STAT) (Table 3), suggesting it contains a JAK/STAT cascade and that these matched proteins are conserved during insect evolution
Care must be taken in draw the conclusion that highly abundant expressed sequence tags (ESTs) play critical roles in symbiosis with RSV, the analysis provided a candidate gene list to further investigate the molecular basis of L. striatellus - RSV interactions

Summary

Introduction

The small brown planthopper (Laodelphax striatellus) is an important agricultural pest that damages rice plants by sap-sucking, and acts as a vector that transmits rice stripe virus (RSV), which can cause even more serious yield loss. Taking advantage of insect transmission, viruses can spread among plant individuals, usually resulting in epidemic outbreaks of viral disease and severe agricultural yield loss. Understanding the biology of vector insects and the viral transmission mechanisms will provide insight into interactions among insects, viruses, and plants, which will promote the development of effective techniques to prevent viral diseases of plants. Besides injuring rice plants (Oryza sativa) by sap-sucking with its piercing-sucking mouthparts, L. striatellus acts as the most important vector of rice stripe virus (RSV, belonging to Tenuivirus) in a persistent and propagative manner [5]. L. striatellus has long been used as a model organism in the study of insect ecology, physiology, biochemistry, as well as molecular interactions between vectors and plant viruses

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