Physiological and biochemical traits of tobacco plants carrying an agrobacterial isopentenyltransferase gene
Transgenic tobacco (Nicotiana tabacum L.) plants were obtained with the constitutive expression of an agrobacterial isopentenyltransferase gene. These transgenic plants produced three times more zeatin riboside than the wild-type plants. Enhanced cytokinin synthesis produced such morphological changes as dwarfism, excessive shoot branching, and loss of roots. The wild-type and transformed plants did not differ in the extent of methylation of ribosomal RNA genes. The enhanced cytokinin synthesis resulted in a 20-50% drop in the chlorophyll content of tobacco leaves. The chloroplasts isolated from the wild-type and transgenic plants, following senescence and cold stress, differed in their rates of oxygen evolution.