The cDNA-amplified fragment length polymorphism technique was applied to isolate the differentially
expressed genes during Bamboo mosaic virus (BaMV) infection on Nicotiana benthamiana plants. One of
the upregulated genes was cloned and predicted to contain a TBC domain designated as NbRabGAP1 (Rab
GTPase activation protein 1). No significant difference was observed in BaMV accumulation in the
NbRabGAP1-knockdown and the control protoplasts. However, BaMV accumulation was 50% and 2% in
the inoculated and systemic leaves, respectively, of the knockdown plants to those of the control plants.
By measuring the spreading area of BaMV infection foci in the inoculated leaves, we found that BaMV
moved less efficiently in the NbRabGAP1-knockdown plants than in the control plants. Transient
expression of the wild type NbRabGAP1 significantly increases BaMV accumulation in N. benthamiana.
These results suggest that NbRabGAP1 with a functional Rab-GAP activity is involved in virus movement.