Research article Molecular characterization of a potato MAP kinase transcriptionally regulated by multiple environmental stresses Flavio Antonio Blanco * , María Eugenia Zanetti 1 , Claudia Anahí Casalongué, Gustavo Raúl Daleo Instituto de Investigaciones Biológicas-Departamento de Biología, Universidad Nacional de Mar del Plata, Funes 3250, CC 1245, 7600 Mar del Plata, Argentina Received 23 July 2005 Available online 16 June 2006 Abstract The MAPK cascade is an evolutionary conserved signaling pathway that links external stimuli with cellular responses. Using polymerase chain reaction (PCR), a DNA fragment corresponding to a Solanum tuberosum MAPK, StMPK1, was isolated. StMPK1 amino acid sequence displayed over 90% identity with tomato MPK1 (LeMPK1) and tobacco SIPK. Southern blot analysis indicated that the gene encoding StMPK1 is present in a single copy in the potato genome. StMPK1 mRNA levels differentially accumulated in potato tuber in response to wounding and to wounding plus Fusarium solani f. sp. eumartii. Transcript accumulation after infection was transient and started earlier than what was observed in wounded tubers. StMPK1 mRNA levels also increased in potato tuber after 24 h of treatment with jasmonic acid (JA) and abscicic acid (ABA), but not in response to ethylene or salicylic acid. In addition, StMPK1 transcript levels increased after a heat-shock treatment at 42 °C. The results suggest that StMPK1 may participate in the cellular responses against multiple environmental stimuli in potato tubers. © 2006 Elsevier SAS. All rights reserved. Keywords: Abscicic acid; Fungal infection; Fusarium eumartii; Heat shock; Jasmonic acid; MAP kinase, Solanum tubersoum; Wounding 1. Introduction Plant defense responses to environmental stresses involve activation of complex and intricate networks of signaling path- ways. One of these pathways is the MAPK (mitogen activated protein kinase) cascade. This signaling module links external stimuli with several cellular responses and is evolutionary con- served among eukaryotic organisms [13,24]. The last compo- nent of this cascade, a MAPK, is a serine/threonine kinase acti- vated by a dual phosphorylation of threonine and tyrosine residues of a TXY motif. These phosphorylations are per- formed by a MAPK kinase (MAPKK), which is in turn acti- vated by an upstream MAKK kinase (MAPKKK). In the last decade, an increasing number of plant MAPKs have been isolated and characterized in dicotyledonous, as well as in monocotyledonous species [1,11,23,24]. Twenty-three MAPKs have been identified in the Arabidopsis thaliana gen- ome and classified according to their sequence homology into four major groups, from A to D [12,13]. Groups A–C contain the phosphorylation motif TEY whereas family D contains the motif TDY. Plant MAPKs can be regulated at mRNA, protein or enzy- matic activity levels in response to several abiotic and biotic stresses, plant hormones, and cell division [4,13,29]. The group A of MAPKs has been implicated in response to oxida- tive stress, cold, drought, wounding, as well as fungal and bac- terial elicitors. AtMPK3 and AtMPK6 are representative mem- bers of group A in Arabidopsis [2,15,19]. Two MAPKs closely related to AtMPK3 and AtMPK6, the tobacco WIPK (wounding-induced protein kinase) and SIPK (salicylic- induced protein kinase), had been previously reported as acti- vated in response to wounding and salicylic acid, respectively [23,32]. Both MAPKs are also activated in tobacco plants in response to pathogen stimuli, including Phytophthora infestans elicitin and tobacco mosaic virus [27,31]. Later on, Holley et al. [11] isolated three MAPKs from tomato plants and charac- www.elsevier.com/locate/plaphy Plant Physiology and Biochemistry 44 (2006) 315–322 Abbreviations: ABA, absicic acid; JA, jasmonic acid; MAPK, mitogenic activated protein kinase; StMPK1, Solanum tuberosum mitogen activated protein kinase. * Corresponding author. E-mail address: fablanco@biol.unlp.edu.ar (F.A. Blanco). 1 Present address: Instituto de Bioquímica y Biología Molecular, Universi- dad Nacional de La Plata, 47 y 115, La Plata (1900), Argentina. Tel.: +54 221 425 0497; Fax: +54 221 422 6947. 0981-9428/$ - see front matter © 2006 Elsevier SAS. All rights reserved. doi:10.1016/j.plaphy.2006.05.005