The association of host proteins with viral replicase complexes has been demonstrated in numerous plus-strand RNA viruses (1, 24), including Bamboo mosaic virus (BaMV). In BaMV, chloroplast phosphoglycerate kinase (PGK) ( 25 ) and HSP90 (Huang et al., unpublished data) have been reported to be required for efficient accumulation of BaMV; where the identity of additional factors associated with the BaMV RdRp complex and proteins involved in satBaMV RNA replication have not yet been recognized. This study identified a host metabolic enzyme, termed GAPDH, that interacts to negatively regulate bamboo mosaic virus (BaMV) and its associated satellite RNA accumulation. The RNA-binding properties of GAPDH have already been documented for numerous viruses ( 9 , 14 , 29 , 41 , 53 , 56 ). However, the interaction of the GAPDH protein with different viral RNAs determines a functionally different mode of regulation on viral replication and translation. For example: GAPDH interacts indirectly with the JEV NS5 protein by binding to the 3′ ends of JEV, resulting in virus-induced redistribution of GAPDH to control the early stage of JEV replication/translation ( 53 ). GAPDH plays an important functional role in tombusvirus replication through retention of the negative-strand viral RNA template in the replication complex to promote asymmetric RNA synthesis ( 48 ). In contrast, GAPDH inhibits viral replication in interaction with other viruses. For example: silencing of GAPDH increases TGEV infection by 2-3 times, demonstrating the anti-TGEV activity of this protein (14). Binding of GAPDH to HAV RNA suppresses cap-independent translation due to destabilization of RNA secondary structure ( 55 ). In our study, a downregulation of GAPDH-C led to a 2- to 3-fold increase in BaMV and satBaMV replication RNA, indicating that GAPDH-C has an inhibitory effect on BaMV and satBaMV infection. Furthermore, an increase in BaMV-GFP was observed on leaves inoculated in GAPDH-C-silenced N. benthamiana, revealing that GAPDH-C functions at early stages while the virus is establishing a successful infection of invaded primary cells. Similarly, when GAPDH-C is transiently expressed, a 70–80% reduction in BaMV accumulation and notable downregulation of BaMV-GFP/satBaMV-GFP was observed in N. benthamiana plants. A similar decrease in TMV accumulation and in the size rather than number of TMV-GFP foci was observed when TARF was transiently expressed in N. benthamiana ( 52 ). Overall, this seems to imply that GAPDH-C expression has a negative effect on BaMV/satBaMV infection.