Local and systemic changes in arginine decarboxylase activity, putrescine levels and putrescine catabolism in wounded oilseed rape

Here we report the effect of mechanical wounding on putrescine biosynthesis and catabolism in oilseed rape (Brassica napus ssp. oleifera). The lamina of first leaves was wounded by crushing with forceps, and first and second leaves were harvested at various intervals over a 24 h period. Levels of free polyamines were measured and activities of enzymes of polyamine biosynthesis and catabolism were assayed in the harvested tissue. Mechanical wounding of the first leaves led to significant, but transient, increases in arginine decarboxylase (ADC) activity and levels of free putrescine in the wounded first leaf and in unwounded second leaves. The increased putrescine appeared to be the result of a combination of increased ADC activity, coupled with reduced putrescine catabolism, as activity of the oxidative enzyme diamine oxidase was significantly reduced following wounding, both locally and systemically. The role of the increased free putrescine in the wound response of oilseed rape is not known, although the possibility that it is used to form putrescine conjugates is worthy of further investigation.