Gene expression induced by chronic ozone in the Mediterranean shrub Phillyrea latifolia: analylis cDNA-AFLP.

Seedlings of Phillyrea latifolia L., a Mediterranean shrub, were exposed for 90 days to 110 nl l –1 ozone (O3). Comparison of the cDNA-amplified fragment length polymorphism (cDNA-AFLP) patterns for treated and control plants allowed the identification and cloning of 88 differential sequences induced by O3. The differential expression of 67 cloned sequenceswas further confirmed byRT-PCR. The functions of 36 cloned sequences, corresponding to seven of the twelve gene functional classes of Arabidopsis, were presumed on the basis of their homology with characterized gene sequences. Ozone induction of genes homologous to 24 of the clones has been reported in other plant species, whereas the induction of the 12 remaining sequences has not been observed before. Ozone activation of these newly identified genes could be a result of the chronic exposure to low O3 concentration, because in most previous studies, acute treatments, involving high O3 dosages, were applied. Possible roles of the cloned sequences in the response of P. latifolia to O3 and other causes of oxidative stress are discussed.