Differentially expressed genes induced by ozone stress in sensitive and tolerant poplar hybrids

The aim of this investigation is i) to isolate ozone-induced genes, after an acute treatment, in two poplar hybrid species characterised by a different susceptibility to O3, and ii) to study the regulatory mechanisms of the genes related with stress tolerance. Cuttings of two poplar hybrid clones (Populus deltoides x maximowiczii, Eridano clone, O3-sensitive, and Populus x euramericana, I-214 clone, O3-tolerant) were grown and submitted to acute O3 fumigation treatment (150 ppb for 5 h). Several differentially regulated cDNA clones were isolated. Most of the transcripts encode proteins involved in stress defence, protein synthesis, cell metabolism and signal transduction and other. Expression analysis of cDNA clones involved in signal transduction showed that most of transcripts level was increased by ozone treatment in both poplar clones. The mRNA accumulation was in some cases higher in the tolerant species, i.e. for cell wall-associated kinase (WAK) and WRKY transcription factors. Notably, WAK was induced by ozone stress only in the tolerant clone.