The Transmission Efficiency of Tomato Yellow Leaf Curl Virus by the Whitefly Bemisia tabaci Is Correlated with the Presence of a Specific Symbiotic Bacterium Species

Abstract

Tomato yellow leaf curl virus (TYLCV) (Geminiviridae: Begomovirus) is exclusively vectored by the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). TYLCV transmission depends upon a 63-kDa GroEL protein produced by the vector's endosymbiotic bacteria. B. tabaci is a species complex comprising several genetically distinct biotypes that show different secondary-symbiont fauna. In Israel, the B biotype harbors Hamiltonella, and the Q biotype harbors Wolbachia and Arsenophonus. Both biotypes harbor Rickettsia and Portiera (the obligatory primary symbionts). The aim of this study was to determine which B. tabaci symbionts are involved in TYLCV transmission using B. tabaci populations collected in Israel. Virus transmission assays by B. tabaci showed that the B biotype efficiently transmits the virus, while the Q biotype scarcely transmits it. Yeast two-hybrid and protein pulldown assays showed that while the GroEL protein produced by Hamiltonella interacts with TYLCV coat protein, GroEL produced by Rickettsia and Portiera does not. To assess the role of Wolbachia and Arsenophonus GroEL proteins (GroELs), we used an immune capture PCR (IC-PCR) assay, employing in vivo-and in vitro-synthesized GroEL proteins from all symbionts and whitefly artificial feeding through membranes. Interaction between GroEL and TYLCV was found to occur in the B biotype, but not in the Q biotype. This assay further showed that release of virions protected by GroEL occurs adjacent to the primary salivary glands. Taken together, the GroEL protein produced by Hamiltonella (present in the B biotype, but absent in the Q biotype) facilitates TYLCV transmission. The other symbionts from both biotypes do not seem to be involved in transmission of this virus.

Endosymbionts and honey bee colony losses?

“…However, endosymbionts such as Spiroplasma and Hamiltonella can also be beneficial for their host's vectorial capacity, e.g. in the whitefly Bemisia tabaci-Tomato yellow leaf curl virus system, Hamiltonella protects viral particles in the vector [6,10].…”

Symbiotic bacteria (Erwinia sp.) in the gut of Frankliniella occidentalis (Thysanoptera: Thripidae) do not affect its ability to transmit tospovirus

“…Negative interactions between gut bacteria and other gut organisms are recorded for the grasshopper Schistocerca gregaria, in which the gut bacterium Enterobacter agglomerans eliminates the entomopathogenic fungi used to control this insect pest (Dillon et al, 2000). In whiteflies (Bemisia tabaci), one species of secondary symbiont, of the Hamiltonella type, produces a specific GroEL protein, which enhances transmission of a plant virus (Tomato yellow leaf curl virus) (Gottlieb et al, 2010). In order to test the above hypothesis postulated for thrips, we compared the success of normal (symbiotic) thrips and bacteria-free (aposymbiotic) larvae and adults of thrips in transmitting virus.…”

A novel groel gene from the endosymbiont of beet leafhopper, Candidatus Sulcia muelleri

“…virus transmission (Morin et al, 2000). Even if the insect vector harbors more than one endosymbiont, only one GroHp derived from one of the endosymbionts has been implicated in virus transmission (Morin et al, 1999;Gottlieb et al, 2010;Rana et al, 2012;Su et al, 2013). GroHp could offer some resistance in transgenic plants which carry the gene for the whitefly endosymbiont GroHp protein.…”

“…The GroEL protein, or its homologues, can be found in all bacteria including endosymbiont bacteria. The function of GroHp in a virus/vector system could involve not only protecting the virus from degradation or from detection by the immune system, but also virus trafficking throughout the vector and preventing virus aggregation or disassembly (van den Heuvel et al, 1994;Morin et al, 1999;Gottlieb et al, 2010).…”