Constitutive and induced resistance to pathogens in Arabidopsis thaliana depends on nitrogen supply

Knowledge about the induced pathogen resistance of plants is rapidly increasing, but little information exists on its dependence on abiotic growing conditions. Arabidopsis thaliana plants that had been cultivated under different nitrogen regimes were treated with BION(R), a chemical resistance elicitor. The activities of three enzyme classes functionally involved in resistance (chitinase, chitosanase and peroxidase) were quantified over 8 d following treatment as resistance markers. Constitutive levels of three markers and the induced level of peroxidase and chitinase activity were significantly lower under limiting nitrogen supply. Under such conditions the increase of chitosanase activity after resistance induction was severely delayed, although the induced maximum activity of chitosanase was not significantly affected. Total soluble protein content decreased during the first 12 h after resistance elicitation. Thereafter, the induced plants cultivated under high N conditions reached higher protein contents than controls, whereas N-limited induced plants continuously had reduced protein contents. A plant's investment in resistance-related compounds can be severely constrained under limiting nitrogen supply.