Abstract: Plants that accumulate the yeast polyadenylate binding protein (yPAB) display a range of abnormalities, including a characteristic chlorosis in leaves to a necrosis and pronounced inhibition of growth. The severity of these abnormalities reflects the levels of yeast PAB expression in the transgenic plants. In contrast, no obvious differences are seen in undifferentiated callus cultures that express the same range of yeast PAB. The expression of the yeast PAB1 gene in plants does not affect expression of the plant PAB gene family or alter poly(A) length in the total RNA population. It is proposed that the yeast PAB1 gene or its product interferes with as yet unidentified functions of PABs, which functions are manifest only in differentiated, developed plants. Surprisingly, transgenic plants expressing the yeast PAB1 gene are also observed to have a systemic acquired resistance (SAR) to bacterial, fungal and viral pathogens.