Molecular characterization of a potato MAP kinase transcriptionally regulated by multiple environmental stresses

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 degrees C. The results suggest that StMPK1 may participate in the cellular responses against multiple environmental stimuli in potato tubers.