Abstract
The potato/tomato psyllid, Bactericerca cockerelli (B. cockerelli), and the Asian citrus psyllid, Diaphorina citri (D. citri), are very important plant pests, but they are also vectors of phloem-limited bacteria that are associated with two devastating plant diseases. B. cockerelli is the vector of Candidatus Liberibacter psyllaurous (solanacearum), which is associated with zebra chip disease of potatoes, and D. citri is the vector of Ca. Liberibacter asiaticus, which is associated with the Huanglongbing (citrus greening) disease that currently threatens the entire Florida citrus industry. Here we used EST sequence information from D. citri to identify potential targets for RNA interference in B. cockerelli. We targeted ubiquitously expressed and gut-abundant mRNAs via injection and oral acquisition of double-stranded RNAs and siRNAs and were able to induce mortality in recipient psyllids. We also showed knockdown of target mRNAs, and that oral acquisition resulted primarily in mRNA knockdown in the psyllid gut. Concurrent with gene knockdown was the accumulation of target specific ∼ 21 nucleotide siRNAs for an abundant mRNA for BC-Actin. These results showed that RNAi can be a powerful tool for gene function studies in psyllids, and give support for continued efforts for investigating RNAi approaches as possible tools for psyllid and plant disease control.
Highlights
The potato/tomato psyllid, Bactericerca cockerelli (B. cockerelli), is a serious pest of potato and tomato in several regions of the world, and is associated with plant diseases including psyllid yellows of tomatoes [1] and zebra chip disease of potatoes [2]
Psyllid yellows is likely associated with feeding damage and toxin production by B. cockerelli, but this psyllid is a vector of the phloem-limited bacterium, Candidatus Liberibacter psyllaurous, which is believed to be the causal agent of zebra chip disease
We demonstrated the induction of specific RNA interference (RNAi) effects in the potato/tomato psyllid (B. cockerelli) by injection and oral acquisition of double-stranded RNAs (dsRNAs) and small interfering RNAs (siRNAs) inducers
Summary
The potato/tomato psyllid, Bactericerca cockerelli (B. cockerelli), is a serious pest of potato and tomato in several regions of the world (http://www.eppo.org/QUARANTINE/Alert _ List / bacteria/ Liberibacter_psyllaurous.htm), and is associated with plant diseases including psyllid yellows of tomatoes [1] and zebra chip disease of potatoes [2]. The biological similarities of HLB to zebra chip, and the phylogenetic conservation of the causal agents of the diseases and their psyllid vectors suggest that success with one insect species, B. cockerelli, will have potential application to the other, D. citri. Most insect RNAi studies have used specific double-stranded RNAs (dsRNAs) as effectors to induce RNAi activity in recipient insects[10]. RNAi activity has been induced by plant-expressed hairpin double-stranded RNAs [22,23,24] These exciting findings highlight the possibility of using RNAi technology for future plant transgene-mediated efforts to control specific insect pest species. Delivery of gene-specific dsRNAs or siRNAs (targeting Actin, ATPase, Hsp or CLIC) by microinjection or by a newly developed oral delivery protocol induced RNAi effects in teneral adult B. cockerelli and decreased survival of recipient psyllids. Our oral delivery system will allow the efficient screening of psyllid candidate gene targets for RNAi as more sequence information (for both B. cockerelli and D. citri) becomes available
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