Abstract
The African sweetpotato weevil (SPW) Cylas puncticollis Boheman is one of the most important constraints of sweetpotato production in Sub-Saharan Africa and yet is largely an uncharacterized insect pest. Here, we report on the transcriptome analysis of SPW generated using an Illumina platform. More than 213 million sequencing reads were obtained and assembled into 89,599 contigs. This assembly was followed by a gene ontology annotation. Subsequently, a transcriptome search showed that the necessary RNAi components relevant to the three major RNAi pathways, were found to be expressed in SPW. To address the functionality of the RNAi mechanism in this species, dsRNA was injected into second instar larvae targeting laccase2, a gene which encodes an enzyme involved in the sclerotization of insect exoskeleton. The body of treated insects showed inhibition of sclerotization, leading eventually to death. Quantitative Real Time PCR (qPCR) confirmed this phenotype to be the result of gene silencing. Together, our results provide valuable sequence data on this important insect pest and demonstrate that a functional RNAi pathway with a strong and systemic effect is present in SPW and can further be explored as a new strategy for controlling this important pest.
Highlights
Sweetpotato Ipomoea batatas (L.) Lam. is an important food security crop in Sub-Saharan Africa (SSA), covering around 1.8 million hectares with an estimated production of 11.3 million tons [1]
The C. puncticollis transcriptome was sequenced to gain insights into the RNA interference (RNAi)-related genes and for further exploration of essential genes to be silenced through RNAi technology
The number of non-significant hits (50.0%) indicates that the C. puncticollis transcriptome contains unknown sequences that are not yet described in the insect protein sequences databases. For those sequences with a significant match, 87.68% of the contigs are most similar to sequences from coleopteran species: 40.31% to the red flour beetle Tribolium castaneum, which is a worldwide pest of stored food products, 36.51% to the mountain pine beetle Dendroctonus ponderosae sequences, which is a serious forest pest [32] and 10.87% to the Asian long-horn beetle Anoplophora glabripennis sequences, found to be destructive of forest trees [33]
Summary
Sweetpotato Ipomoea batatas (L.) Lam. is an important food security crop in Sub-Saharan Africa (SSA), covering around 1.8 million hectares with an estimated production of 11.3 million tons [1]. As this crop is highly adaptable to areas with seasonal rainfalls or long drought periods, it improves consumers’ livelihoods and fulfills their daily food needs for subsistence farmers [2, 3]. Sweetpotato production can be devastated by the infestation of two PLOS ONE | DOI:10.1371/journal.pone.0115336. Transcriptome and RNAi in African Sweetpotato Weevil Sweetpotato production can be devastated by the infestation of two PLOS ONE | DOI:10.1371/journal.pone.0115336 January 15, 2015
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