Genome-wide miRNA and piRNA profiles of the vector whitefly, Bemisia tabaci during feeding on Tomato yellow leaf curl virus-infected tomato

The whitefly, Bemisia tabaci MEAM1 is a devastating vector capable of transmitting hundreds of plant viruses, including Tomato yellow leaf curl virus (TYLCV), to important food and fiber crops. Here we performed genome-wide profiling of micro RNAs (miRNAs) and piwi-interacting RNAs (piRNAs) in whiteflies after feeding on TYLCV-infected tomato or uninfected tomato for 24, 48 and 72 h. Overall, 160 miRNAs were discovered, 68 of which were conserved and 92 were B. tabaci-specific miRNAs. Majority of the genes that were predicted to be targeted by miRNAs had gene ontologies related to metabolic processes. We identified two miRNAs that were differentially expressed in whiteflies when fed on TYLCV-infected tomato compared to whiteflies that fed on uninfected tomato. The identified piRNAs were expressed as clusters throughout the whitefly genome. A total of 53 piRNA clusters were expressed across all time points and treatments, while 5 piRNA clusters were exclusively expressed in whiteflies that fed on TYLCV-infected tomato, and 24 clusters were exclusively expressed in whiteflies that fed on uninfected tomato. Approximately 62% of all identified piRNAs were derived from non-coding sequences that included intergenic regions, introns, and UTRs with unknown functions. The remaining 38% of piRNAs were derived from coding sequences (CDS) and repeat elements. Transposable elements targeted by piRNA clusters included both class I retrotransposons such as Gypsy, Copia, and LINEs and class II DNA transposons such as MITE, hAT, and TcMar. Lastly, six protein coding genes were targeted in whiteflies that fed on TYLCV-infected tomato. Information on how TYLCV influences miRNA and piRNA expression in whiteflies provides a greater understanding of regulatory pathways involved in mediating whitefly-virus interactions, and will facilitate the identification of novel targets for RNAi control. Deep sequencing of small RNAs was isolated from total RNA from whiteflies fed on either TYLCV-infected tomato or uninfected tomato for 24, 48, and 72 h. Three biological replicates were performed for each time point.