Text by Daniel K. Hasegawa and Kai-Shu Ling
Different and common whitefly genes are induced by two viruses with distinct modes of transmission
The whitefly, Bemisia tabaci is a notorious virus vector capable of transmitting hundreds of plant viruses that affect agricultural production and food security on a global scale. B. tabaci-transmitted viruses cause diseases on vegetables, ornamentals, legumes, cassava and cotton, resulting in serious yield losses. Viruses transmitted by B. tabaci are classified into five genera (Begomovirus, Crinivirus, Carlavirus, Ipomovirus and Torradovirus) and have different modes of transmission. However, genetic mechanisms involved in virus circulation and transmission by whitefly have not been well characterized.
The basis for this study was to gain a broader understanding of how whiteflies respond to feeding on agricultural crops infected by viruses with different modes of transmission. Therefore, we analyzed gene expression of the whitefly, B. tabaci in response to feeding on tomato infected with the persistently-transmitted begomovirus, tomato yellow leaf curl virus (TYLCV), which poses a serious threat to tomato production worldwide. RNA-seq was performed on whiteflies that fed on either virus-free or TYLCV-infected tomato for 24, 48, or 72 h. The data were then compared to the results generated as part of a collaborative project with Bill Wintermantel’s lab (USDA-ARS, Salinas, CA), where whiteflies were fed on tomato infected with the semi-persistently-transmitted crinivirus, tomato chlorosis virus (ToCV) under the same conditions (Kaur et al. 2017).
We were surprised by the number of genes that were differentially expressed in whiteflies. Fewer than 100 differentially expressed genes were identified in whiteflies that fed on TYLCV-infected tomato, whereas over 1,000 genes were identified in whiteflies fed on ToCV-infected tomato. Interestingly though, the trend across the three time points was very similar between the two viruses, with higher numbers of genes at 24 and 72 h, and very few genes differentially expressed at 48 h. Furthermore, numerous common genes were identified in both virus treatments, suggesting that two viruses with different modes of transmission may have similar effects on B. tabaci.
The “aha” moment came when several differentially expressed genes identified in the TYLCV-whitefly study were found to be similar to those identified in other vector-pathogen systems, including cathepsin genes (aphid-luteovirus system) and a hemocyanin gene, which was identified during psyllid transmission of the bacterial pathogen that causes citrus greening disease. Overall, these data provide genetic targets that are distinct and common during insect vector transmission of a wide range of viruses; information that may be useful in applying RNA interference or other methods for management of whiteflies.
Top left: Experimental design for comparing whitefly, Bemisia tabaci gene expression over time in response to feeding on tomatoes infected with the begomovirus, tomato yellow leaf curl virus (TYLCV) or the crinivirus, tomato chlorosis virus (ToCV).
Top Right: Number of B. tabaci genes differentially expressed after feeding on tomato plants infected with either the crinivirus, ToCV, or the begomovirus, TYLCV.
Bottom left: Male and female whitefly, B. tabaci.
Bottom right: Predicted structure of the B. tabaci hemocyanin protein, which was over expressed at two time points in whiteflies that fed on TYLCV-infected tomatoes.
- Kaur, N., Chen, W., Zheng, Y., Hasegawa, D.K., Ling, K.-S., Fei, Z., Wintermantel, W.M. 2017. Transcriptome analysis of the whitefly, Bemisia tabaci MEAM1 on tomato infected with the crinivirus, Tomato chlorosis virus, identifies a temporal shift in gene expression and differential regulation of novel orphan genes. BMC Genomics. 18:370.
Introducing the authors
Daniel K. Hasegawa (Left) is a postdoctoral research associate and Kai-Shu Ling (Right) is a Research Plant Pathologist working at the U.S. Department of Agriculture, Agricultural Research Service, U.S. Vegetable Laboratory in Charleston, South Carolina, USA.
About the Research
Comparative transcriptome analysis reveals networks of genes activated in the whitefly, Bemisia tabaci when fed on tomato plants infected with Tomato yellow leaf curl virus
Virology, Volume 513, 1 January 2018, Pages 52-64