Gene expression profiling in wounded and systemic leaves of Fagus sylvatica reveals up-regulation of ethylene and jasmonic acid signalling.

Wounding is a crucial threat to plants because of the physical damage caused and the possible entry of pathogens. Little is known about the wound reaction in forest trees. Therefore, leaves of young beech trees were wounded and the transcriptional response of wounded leaves and leaves directly above and below was analysed. A total of 123 genes exhibited significant regulation. The magnitude of regulation was slightly weaker in the downward leaves but the regulation pattern resembles that of the local and upward reactions. Thus, the signal was transduced in both vertical directions. Genes exhibiting major regulation lacked functional assignment or belonged to signalling, transcription and defence categories. Signalling included activation of transcripts in the calcium and ethylene pathways. There was also evidence for activation of jasmonic acid signalling, but no activation of jasmonic acid-responsive PR (pathogenesis-related) genes was observed. Moreover, repression of salicylic acid responsive defence was measured. Metabolic changes included induction of a core gene of the phenylpropanoid pathway, while energy metabolism exhibited down-regulation. These results support the conclusion that young beech trees might give up leaves and/or reduce leaf energy content after an attack so as to deprive a putative herbivore of a nutrient supply, instead of investing much energy in leaf defence.