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.

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The whitefly Bemisia tabaci is a major pest to agriculture. Adults are able to fly for long distances and to colonize staple crops, herbs and ornamentals, and to vector viruses belonging to several important taxonomic groups. During their early development, whiteflies mature from eggs through several nymphal stages (instars I to IV) until adults emerge from pupae. We aim at reducing whitefly populations by inhibiting the emergence of adults from nymphs. Here we targeted dystrophin, a conserved protein essential for the development of the muscle system in humans, other animals and insects. We have exploited the fact that whitefly nymphs developing on tomato leaves feed from the plant phloem via their stylets. Thus, we delivered dystrophin‐silencing double‐stranded RNA to nymphs developing on leaves of tomato plantlets with their roots bathing in the silencing solution. Downregulation of dystrophin expression occurred mainly in pupae. Dystrophin silencing induced also the downregulation of the dystrophin‐associated protein genes actin and tropomyosin, and disrupted F‐actin. Most significantly, the treatment inhibited the emergence of adults from pupae, suggesting that targeting dystrophin may help to restrain whitefly populations. This study demonstrates for the first time the important role of dystrophin in the development of a major insect pest to agriculture.

Abstract-Two approaches for monitoring atenolol (ATL) were applied: an immunochemical assay and a competitive-binding assay, based on the interaction between ATL and its target receptor, b1 adrenergic receptor (b1AR). Polyclonal antibodies (Abs) for ATL were generated, and a highly specific microplate immunochemical assay, that is, an enzyme-linked immunosorbent assay (ELISA), for its detection was developed. The ATL ELISA exhibited I50 and limit of detection (I20) values of 0.15 AE 0.048 and 0.032 AE 0.016 ng/ml, respectively, and the Abs did not cross-react with any of the tested beta-blocker drugs. Furthermore, a human b1AR (h-b1AR) was stably expressed in Spodoptera frugiperda cells (Sf9). The receptor was employed to develop a competitive-binding assay that monitored binding of ATL in the presence of isoproteranol by quantification of secondary messenger, cyclic adenosine monophosphate (cAMP), levels in the transfected cells. The assay showed that the recombinant h-b1AR was functional, could bind the agonistic ligand isoproterenol as well as the antagonist ATL, as indicated by a dose-dependent elevation of cAMP in the presence of isoproteranol, and decrease after ATL addition. The highly efficient and sensitive ELISA and the receptor assay represent two methods suitable for efficient and cost-effective large-scale, high-throughput monitoring of ATL in environmental, agricultural, and biological samples. Environ.