The yeast polyadenylate-binding protein (PAB1) gene acts as a disease lesion mimic gene when expressed in plants

We have expressed the gene (PAB1) encoding the yeast polyadenylate-binding protein (Pab1p) in tobacco. Plants that accumulate the Pab1p display a rang e of abnormalities, ranging from a characteristic chlorosis in leaves to a necrosis and large inhibition of growth. The severity of these abnormalitie s reflects the levels of yeast Pab1p expression in the transgenic plants. I n contrast, no obvious differences could be seen in callus cultures between the transgene and vector control. Plants that display PAB-associated abnor malities were resistant to a range of plant pathogens, and had elevated lev els of expression of a pathogenesis-related gene. These two properties - im pairment of growth and induction of defense responses - indicate that the y east PAB1 gene can act as a disease lesion mimic gene in plants.