THE PR-1A PROMOTER CONTAINS A NUMBER OF ELEMENTS THAT BIND GT-1-LIKE NUCLEAR FACTORS WITH DIFFERENT AFFINITY

The 900 bp promoter region of the tobacco PR-1a gene was divided into eight fragments using PCR. The fragments were tested for their ability to bind to nuclear factors isolated from tobacco leaf. Band shift ass ays demonstrated that all but one of the fragments specifically intera cted with nuclear proteins. From competition experiments it was determ ined that the same nuclear factors bind various promoter fragments wit h different affinity. Moreover, efficient competition with a synthetic tetramer of box II of the rbcS promoter (Green PJ et al., EMBO J 13 ( 1988) 4035-4044) indicated that GT-l-like nuclear factors are involved in these interactions. Furthermore, in comparison to extracts from un treated plants, nuclear protein preparations from tobacco mosaic virus -infected tobacco showed a reduced GT-1 binding activity. These result s will be discussed in relation to induced PR-1a gene expression.