Over-expression of the oat arginine decarboxylase cDNA in transgenic rice (Oryza sativa L.) affects normal development patterns in vitro and results in putrescine accumulation in transgenic plants

Transgenic rice (Oryza sativa L.) cell lines and plants expressing an oat arginine decarboxylase (Anc) cDNA under the control of the CaMV 35 S promoter were recovered using particle bombardment. Molecular analyses confirmed stable integration of the transgene and active transcription (mRNA). A four- to sevenfold increase in arginine decarboxylase (ADC) activity was observed in transformed plants compared to wild-type controls. Biochemical analysis of cellular polyamines (PAs) indicated up to fourfold increase in putrescine (Put) levels in transgenic callus and regenerated plants. This is the first report which demonstrates an increase in PA levels in plants engineered with the Ade gene. Implications of this increase are discussed in terms of development, physiology and nutrition. We observed a correlation between high levels of Ade gene expression and inability of callus tissue to develop normally into differentiated plants. This correlates well with reports in other species, in which perturbation of the PA pathway using genes involved in PA biosynthesis results in aberrant phenotypes. We have shown for the first time that PA biosynthesis can be manipulated in cereal species using genetic engineering.