FIG. 1.

Detection of PSTVd RNA-binding protein VIRP1. A total of about 600,000 plaques from a cDNA expression library from tomato leaves were subjected to a primary screening, by using a longer-than-unit-length PSTVd RNA transcript (57) as a radioactively labeled probe. (A) The tomato cDNA expression library was plated at ca. 5,000 PFU/plate. The black arrow shows the signal corresponding to the viroid binding protein 1 clone after a primary screening. (B) The clone picked from the primary screening was plated at a density of 25 PFU/plate, and the PSTVd RNA-binding properties of positive clone 1 were confirmed by secondary screening. Plaque lift and binding assays with α-³²P-labeled RNA transcripts were performed as described in Materials and Methods.