Patterns of plant-mediated whitefly-begomovirus interactions
The effects of a begomovirus on a whitefly vector, or vice versa, via their shared host plants can be mutualistic, neutral or negative (Jiu et al. 2007; Liu et al. 2009, 2010; Li et al. 2011). However, in contrast to a preliminary pattern of improved performance of vectors on virus-infected plants that has been observed with persistently transmitted RNA viruses, the numbers of cases exhibiting mutualistic, neutral or negative effects in the indirect interactions between begomoviruses and whiteflies appear evenly distributed.
Mechanisms of plant-mediated positive effects between viruses and vectors
With regard to the mechanisms of plant-mediated positive effects, a recent study demonstrated that when tobacco plants were infected with Tomato yellow leaf curl China virus (TYLCCNV), the jasmonic acid defenses and terpenoid synthesis in the plants were repressed but significant changes of nutrition were not detected, indicating that plant defenses play a key role in mediating the interactions in this system (Zhang et al. 2012; Luan et al. 2013). Moreover, infection of tobacco with TYLCCNV enhanced nutritional assimilation and vitellogenesis of whiteflies (Guo et al. 2012; Wang et al. 2012). Interestingly, with the same virus-plant system, while the invasive B whitefly is able to acquire benefits from virus-infected plants, the indigenous whiteflies are unable to do so (Jiu et al. 2007). Efforts are being devoted to reveal the mechanisms underlying the disparity between invasive and indigenous whiteflies.
Figure: Performance of the invasive B whitefly and the indigenous ZHJ1 whitefly on uninfected tobacco plants and plants infected by Tobacco curly shoot virus (TbCSV) or Tomato yellow leaf curl China virus (TYLCCNV) (Jiu et al. 2007).
Figure: Co-infection of betasatellite TYLCCNB with TYLCCNV (a) or the bC1 protein encoded by betasatellite (b) suppresses relative expression of jasmonic acid related genes in tobacco plants (Zhang et al. 2012).
Figure: Digital gene expression (DGE) and qRT-PCR revealed that the relative expression of the tobacco terpenoid synthesis gene 5-epi-aristolochene synthase was at higher levels in whitefly-infested plants, declined in virus-infected plants, and decreased slightly in co-infested plants (Luan et al. 2013).
Endosymbionts and their roles in whitefly-begomovirus-plant interactions
Work has been underway to identify endosymbionts that may be involved in virus transmission and infectivity through molecular approaches. In addition, we have been investigating the key whitefly proteins involved in virus transmission.