Identification of differential expressed gene induced by ozone stress in tolerant and sensitive Populus spp.

Ground-level concentrations of ozone have rapidly risen over the past century: present-day concentrations of ozone commonly exceed the accepted threshold of 40 ppb and the gas is now recognized to be the most damaging air pollutant to which vegetation is exposed in many parts of Central/Southern Europe, North/South America and Asia. Plant subjected to elevated concentrations of ozone undergo several biochemical changes, that are the direct result of a qualitative and quantitative modification of gene expression. With the aim to identify differentially expressed genes after the exposition to an acute ozone dose a suppression subtractive hybridisation technique was used in two poplar species characterised by a different sensibility to this kind of pollutant (sensitive and tolerant to ozone). By using SSH, cDNA subtracted libraries were obtained both for ozone-treated sensitive clone and for ozone-treated treated clone and after a primary screening we have isolated several ozone differentially regulated cDNA clones. Sequence analysis showed that selected cDNAs include those with a putative role in the antioxidative response, the hypersensitive response, signal transduction, and some genes with unknow function. The isolated cDNAs include e.g. a sequence containig leucine-rich repeat (LPR) (sensitive clone) that have been predicted to be present in proteins that mediated intercellular or intracellular signalling and a cDNA sequence (tolerant clone) that presents a conserved domain typical of transcription factors belonging to the WRKY superfamily that include members involved in the regulation of various physiological program. The expression of some of the most interesting isolated clones has been analysed furthermore.