Abstract
The whitefly Bemisia tabaci is a major pest to agricultural crops. It transmits begomoviruses, such as Tomato yellow leaf curl virus (TYLCV), in a circular, persistent fashion. Transcriptome analyses revealed that B. tabaci knottin genes were responsive to various stresses. Upon ingestion of tomato begomoviruses, two of the four knottin genes were upregulated, knot-1 (with the highest expression) and knot-3. In this study, we examined the involvement of B. tabaci knottin genes in relation to TYLCV circulative transmission. Knottins were silenced by feeding whiteflies with knottin dsRNA via detached tomato leaves. Large amounts of knot-1 transcripts were present in the abdomen of whiteflies, an obligatory transit site of begomoviruses in their circulative transmission pathway; knot-1 silencing significantly depleted the abdomen from knot-1 transcripts. Knot-1 silencing led to an increase in the amounts of TYLCV ingested by the insects and transmitted to tomato test plants by several orders of magnitude. This effect was not observed following knot-3 silencing. Hence, knot-1 plays a role in restricting the quantity of virions an insect may acquire and transmit. We suggest that knot-1 protects B. tabaci against deleterious effects caused by TYLCV by limiting the amount of virus associated with the whitefly vector.
Highlights
The whitefly Bemisia tabaci is a major agricultural pest worldwide, damaging plants by sucking their phloem and by transmitting many viruses [1]
Out of the Four Whitefly Knottin Genes, knot-1 Shows the Highest Levels of Expression. It Is Upregulated upon Ingestion of Tomato yellow leaf curl virus (TYLCV)
The region used for Quantitative RT-PCR (qPCR) was separated from the region that served as template for dsRNA synthesis
Summary
The whitefly Bemisia tabaci is a major agricultural pest worldwide, damaging plants by sucking their phloem and by transmitting many viruses [1]. Begomovirus, family Geminiviridae) are the most harmful. Their genome consists of one (monopartite) or two (bipartite) circular ssDNA components of approximately 2800 nucleotides each. Tomato yellow leaf curl virus (TYLCV) is one of the most destructive monopartite begomoviruses [2]. The TYLCV complex includes several species and numerous isolates [3]. The TYLCV disease is managed by frequent applications of insecticides to contain the whitefly populations in the field and greenhouses, and by breeding resistant cultivars [2]
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