Abstract
Bamboo mosaic virus (BaMV) is a single-stranded positive-sense RNA virus. One of the plant glutathione S-transferase (GST) genes, NbGSTU4, responds as an upregulated gene in Nicotiana benthamiana post BaMV infection.In order to identify the role of NbGSTU4 in BaMV infection, the expression of NbGSTU4 was knocked down using a virus-induced gene silencing technique or was transiently expressed in N. benthamiana in BaMV inoculation.The results show a significant decrease in BaMV RNA accumulation when the expression level of NbGSTU4 is reduced; whereas the viral RNA accumulation increases when NbGSTU4 is transiently expressed. Furthermore, this study identified that the involvement of NbGSTU4 in viral RNA accumulation occurs by its participation in the viral early replication step. The findings show that the NbGSTU4 protein expressed from Escherichia coli can interact with the 3′ untranslated region (UTR) of the BaMV RNA in vitro in the presence of glutathione (GSH). The addition of GSH in the in vitro replication assay shows an enhancement of minus-strand but not plus-strand RNA synthesis.The results suggest that the plant GST protein plays a role in binding viral RNA and delivering GSH to the replication complex to create a reduced condition for BaMV minus-strand RNA synthesis.
Highlights
Glutathione S-transferases (GSTs) are grouped into a large family of both eukaryotes and prokaryotes and catalyze a variety of reactions (Sheehan et al, 2001; Dixon et al, 2002; Allocati et al, 2009)
An experiment using the Tobacco rattle virus (TRV)-based virus-induced gene silencing (VIGS) technique (Lin et al, 2007) to knock down the expression of this gene in N. benthamiana showed that the accumulation levels of the Bamboo mosaic virus (BaMV) coat protein in the knockdown plants was reduced to 51% of that of the control plants
No significant interference occurred in the accumulation of Cucumber mosaic virus (CMV) and Tobacco mosaic virus (TMV) when inoculated into the knockdown plants (Fig. 1a,b)
Summary
Glutathione S-transferases (GSTs) are grouped into a large family of both eukaryotes and prokaryotes and catalyze a variety of reactions (Sheehan et al, 2001; Dixon et al, 2002; Allocati et al, 2009). Plant GSTs were first recognized in 1970, and have been proven to play a role in the detoxification occurring in herbicide injuries (Frear & Swanson 1970). These plant GSTs are classified into eight distinct groups: phi, tau, theta, zeta, lambda, DHAR, TCHQD and microsomal (Edwards & Dixon, 2005). In Arabidopsis, 48 GST-like genes were grouped into 28 tau, 13 phi, 3 theta, 2 zeta and 2 lambda GSTs (Dixon et al, 2002); 42 maize GST-like genes were grouped into 12 phi, 28 tau and 2 zeta GSTs; and 25 soybean GST-like genes were grouped into 20 tau, 1 zeta and 4 phi GSTs
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