Regulation of nicotine biogenesis. 3. Biochemical basis of increased nicotine biogenesis by urea in tissue cultures of tobacco

Abstract

Floral bud callus of Nicotiana tabacum L. var. Anand-2 could be grown on Murashige and Skoog medium with 10 mM urea as sole nitrogen source. Urea-treated tissues showed elevated nicotine content over the control. Activities of phenylalanine aminotransferase and tyrosine aminotransferase did not show close correspondence with growth or nicotine synthesis, whereas ornithine aminotransferase (OAT) activity exhibited correlation with nicotine biogenesis. Urea-treated callus showed higher OAT activity than the control. The activity of ornithine transcarbamylase (OTC) showed inverse correlation with nicotine synthesis. OTC and arginase activities were suppressed in urea-treated tissues. The implication of the results is discussed.