Dataset Information

Transcriptome-wide responses of adult melon thrips (Thrips palmi) associated with capsicum chlorosis virus infection.

ABSTRACT: Thrips palmi is a widely distributed major agricultural pest in the tropics and subtropics, causing significant losses in cucurbit and solanaceous crops through feeding damage and transmission of tospoviruses. Thrips palmi is a vector of capsicum chlorosis virus (CaCV) in Australia. The present understanding of transmission biology and potential effects of CaCV on T. palmi is limited. To gain insights into molecular responses to CaCV infection, we performed RNA-Seq to identify thrips transcripts that are differentially-abundant during virus infection of adults. De-novo assembly of the transcriptome generated from whole bodies of T. palmi adults generated 166,445 contigs, of which ~24% contained a predicted open reading frame. We identified 1,389 differentially-expressed (DE) transcripts, with comparable numbers up- (708) and down-regulated (681) in virus-exposed thrips compared to non-exposed thrips. Approximately 59% of these DE transcripts had significant matches to NCBI non-redundant proteins (Blastx) and Blast2GO identified provisional functional categories among the up-regulated transcripts in virus-exposed thrips including innate immune response-related genes, salivary gland and/or gut-associated genes and vitellogenin genes. The majority of the immune-related proteins are known to serve functions in lysosome activity and melanisation in insects. Most of the up-regulated oral and extra-oral digestion-associated genes appear to be involved in digestion of proteins, lipids and plant cell wall components which may indirectly enhance the likelihood or frequency of virus transmission or may be involved in the regulation of host defence responses. Most of the down-regulated transcripts fell into the gene ontology functional category of 'structural constituent of cuticle'. Comparison to DE genes responsive to tomato spotted wilt virus in Frankliniella occidentalis indicates conservation of some thrips molecular responses to infection by different tospoviruses. This study assembled the first transcriptome in the genus Thrips and provides important data to broaden our understanding of networks of molecular interactions between thrips and tospoviruses.

SUBMITTER: Widana Gamage SMK

PROVIDER: S-EPMC6286046 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Transcriptome-wide responses of adult melon thrips (Thrips palmi) associated with capsicum chlorosis virus infection.

Widana Gamage Shirani M K SMK Rotenberg Dorith D Schneweis Derek J DJ Tsai Chi-Wei CW Dietzgen Ralf G RG

PloS one 20181207 12

Thrips palmi is a widely distributed major agricultural pest in the tropics and subtropics, causing significant losses in cucurbit and solanaceous crops through feeding damage and transmission of tospoviruses. Thrips palmi is a vector of capsicum chlorosis virus (CaCV) in Australia. The present understanding of transmission biology and potential effects of CaCV on T. palmi is limited. To gain insights into molecular responses to CaCV infection, we performed RNA-Seq to identify thrips transcripts ...[more]

PMID: 30532222

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Project description:The melon thrips, Thrips palmi is a serious pest and vector for plant viruses on a wide range of economically important crops. DNA barcoding evidenced the presence of cryptic diversity in T. palmi and that warrants exhaustive molecular studies. Our present study is on decoding the first complete mitochondrial genome of T. palmi (15,333 bp) through next-generation sequencing (NGS). The T. palmi mt genome contains 37 genes, including 13 Protein coding genes (PCGs), two ribosomal RNA (rRNAs), 22 transfer RNA (tRNAs), and two control regions (CRs). The majority strand of T. palmi revealed 78.29% A+T content, and 21.72% G+C content with positive AT skew (0.09) and negative GC skew (-0.06). The ATN initiation codons were observed in 12 PCGs except for cox1 which have unique start codon (TTG). The relative synonymous codon usage (RSCU) analysis revealed Phe, Leu, Ile, Tyr, Asn, Lys and Met were the most frequently used amino acids in all PCGs. The codon (CGG) which is assigned to Arginine in most insects but absent in T. palmi. The Ka/Ks ratio ranges from 0.078 in cox1 to 0.913 in atp8. We observed the typical cloverleaf secondary structure in most of the tRNA genes with a few exceptions; absence of DHU stem and loop in trnV and trnS, absence of DHU loop in trnE, lack of T-arm and loop in trnN. The T. palmi gene order (GO) was compared with ancestral GO and observed an extensive gene arrangement in PCGs, tRNAs and rRNAs. The cox2 gene was separated from the gene block 'cox2-trnL2' in T. palmi as compared with the other thrips mt genomes, including ancestor GO. Further, the nad1, trnQ, trnC, trnL1, trnV, trnF, rrnS, and rrnL were inversely transpositioned in T. palmi GO. The gene blocks 'trnQ-trnS2-trnD' and 'trnN-trnE-trnS1-trnL1' seems to be genus specific. The T. palmi mt genome contained 24 intergenic spacer regions and 12 overlapping regions. The 62 bp of CR2 shows the similarity with CR1 indicating a possible duplication. The occurrence of multiple CRs in thrips mt genomes seems to be a derived trait which needs further investigation. Although, the study depicted extensive gene rearrangements in T. palmi mt genome, but the negative GC skew reflects only strand asymmetry. Both the ML and BI phylogenetic trees revealed the close relationships of Thrips with Scirtothrips as compared to Frankliniella. Thus, more mt genomes of the diverse thrips species are required to understand the in-depth phylogenetic and evolutionary relationships.

Project description:BackgroundCapsicum chlorosis virus (CaCV) is an emerging pathogen of capsicum, tomato and peanut crops in Australia and South-East Asia. Commercial capsicum cultivars with CaCV resistance are not yet available, but CaCV resistance identified in Capsicum chinense is being introgressed into commercial Bell capsicum. However, our knowledge of the molecular mechanisms leading to the resistance response to CaCV infection is limited. Therefore, transcriptome and expression profiling data provide an important resource to better understand CaCV resistance mechanisms.Methodology/principal findingsWe assembled capsicum transcriptomes and analysed gene expression using Illumina HiSeq platform combined with a tag-based digital gene expression system. Total RNA extracted from CaCV/mock inoculated CaCV resistant (R) and susceptible (S) capsicum at the time point when R line showed a strong hypersensitive response to CaCV infection was used in transcriptome assembly. Gene expression profiles of R and S capsicum in CaCV- and buffer-inoculated conditions were compared. None of the genes were differentially expressed (DE) between R and S cultivars when mock-inoculated, while 2484 genes were DE when inoculated with CaCV. Functional classification revealed that the most highly up-regulated DE genes in R capsicum included pathogenesis-related genes, cell death-associated genes, genes associated with hormone-mediated signalling pathways and genes encoding enzymes involved in synthesis of defense-related secondary metabolites. We selected 15 genes to confirm DE expression levels by real-time quantitative PCR.Conclusion/significanceDE transcript profiling data provided comprehensive gene expression information to gain an understanding of the underlying CaCV resistance mechanisms. Further, we identified candidate CaCV resistance genes in the CaCV-resistant C. annuum x C. chinense breeding line. This knowledge will be useful in future for fine mapping of the CaCV resistance locus and potential genetic engineering of resistance into CaCV-susceptible crops.

Dataset Information

Transcriptome-wide responses of adult melon thrips (Thrips palmi) associated with capsicum chlorosis virus infection.

Publications

Transcriptome-wide responses of adult melon thrips (Thrips palmi) associated with capsicum chlorosis virus infection.

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