Original article The catecholamine biosynthesis route in potato is affected by stress Anna S ´ wiVdrych a , Katarzyna Lorenc-Kukula a , Aleksandra Skirycz a , Jan Szopa a,b, * a Institute of Biochemistry and Molecular Biology, University of Wroclaw, Przybyszewskiego Street 63/77, 51-148 Wroclaw, Poland b Department of Plant Physiology, University of Szczecin, Waa ˛ska Street 13, 71-415 Szczecin, Poland Received 16 April 2004; accepted 6 July 2004 Available online 29 July 2004 Abstract The catecholamine compounds in potato (Solanum tuberosum L.) leaves and tubers have been identified by gas chromatography coupled to mass spectrometry (GC-MS) measurements. The finding that the catecholamine level is dramatically increased upon tyrosine decarboxylase (TD) overexpression potentiates the investigation on their physiological significance in plants. It was then evidenced that catecholamines play an important role in regulation of starch–sucrose conversion in plants. In this paper we investigated catecholamine biosynthetic pathway in potato plants exposed to the different stress conditions. The activation of TD (EC 4.1.1.25), tyrosine hydroxylase (TH, EC 1.14.18.1) and L-Dopa decarboxylase (DD, EC 4.1.1.25) was a characteristic feature of the potato leaves treated with abscisic acid (ABA). In high salt condition only TD activity was increased and in drought both TH and DD were activated. UV light activated predominantly DD activity. Leaves of plants grown in the dark and in red light circumstances were characterized by significantly decreased activities of all the three enzymes whereas those grown in cold were characterized by the decreased activity of DD only. In all, stress conditions the normetanephrine level and thus catecholamine catabolism was significantly decreased. Increased catecholamine level in TD-overexpressing potato resulted in enhanced pathogen resistance. Our data suggest that plant catecholamines are involved in plant responses towards biotic and abiotic stresses. It has to be pointed out that this is the first report proposing catecholamine as new stress agent compounds in plants. © 2004 Elsevier SAS. All rights reserved. Keywords: Catecholamines; L-Dopa decarboxylase; Tyrosine decarboxylase; Tyrosine hydroxylase; Solanum tuberosum; Stress response; Transgenic potato plant 1. Introduction Catecholamines are a group of biogenic amines possess- ing a 3,4-dihydroxysubstituted-phenyl ring. Dopamine, norepinephrine, epinephrine and their derivatives are wide- spread in animals and have also been identified by gas chro- matography coupled to mass spectrometry (GC-MS) in po- tato plant [18]. The biochemical role of catecholamines in animal cells is well studied. They act as neurotransmitters but the best- understood example of the hormonal action of epinephrine and norepinephrine in mammals is regulation of glycogen metabolism. Mobilization of glycogen is accompanied by inhibition of glycogen synthesis. Such double control pre- vents futile cycles to take place. The physiological action of catecholamines in animal cells is mediated by their interac- tion with G-protein coupled receptors that stimulate or in- hibit the enzyme adenylyl cyclase (AC). In most animal cells cyclic AMP (cAMP) exerts its effect by activating cAMP- dependent, serine–threonine protein kinase (PKA). Both epi- nephrine and norepinephrine are synthesized and released from the medulla of the mammalian adrenal gland. The biosynthesis of catecholamine is initiated onto two ways starting from tyrosine. Hydroxylation of tyrosine by tyrosine hydroxylase (TH) or tyrosine decarboxylation by tyrosine decarboxylase (TD) is the initial step followed by dopamine hydroxylation to norepinephrine and subsequent methylation to epinephrine. It should be pointed out that TD is also suggested to conduct L-3,4-dihydroxy phenyl alanin (L-Dopa) decarboxylation [2]. Catecholamine catabolism starts via methylation of the hydroxyl group of the catechol Abbréviations: ABA, abscisic acid; DD, L-Dopa decarboxylase; GC- MS, gas chromatography coupled to mass spectrometry; SA, salicylic acid; TD, tyrosine decarboxylase; TH, tyrosine hydroxylase. * Corresponding author. E-mail address: szopa@ibmb.uni.wroc.pl (J. Szopa). Plant Physiology and Biochemistry 42 (2004) 593–600 www.elsevier.com/locate/plaphy 0981-9428/$ - see front matter © 2004 Elsevier SAS. All rights reserved. doi:10.1016/j.plaphy.2004.07.002