Ozone-Induced Biochemical and Molecular Changes in IVitis vinifera/I Leaves and Responses to IBotrytis cinerea/I Infections

To investigate how plants cope with multi-stress conditions, we analyzed the biochemical and molecular changes of Vitis vinifera leaves subjected to single or sequential double stresses (infection by Botrytis cinerea (Bc) and ozone (O[sub.3], 100 ppb for 3 h) treatment). In Bc[sup.+]/O[sub.3] [sup.−] leaves, the hydrogen peroxide (H[sub.2]O[sub.2]) induction (observed at 12 and 24 h from the end of treatment (FET)) triggered a production of ethylene (Et; +35% compared with Bc[sup.−]/O[sub.3] [sup.−] leaves), which was preceded by an increase of salicylic acid (SA; +45%). This result confirms a crosstalk between SA- and Et-related signaling pathways in lesion spread. The ozone induced an early synthesis of Et followed by jasmonic acid (JA) and SA production (about 2-fold higher), where Et and SA signaling triggered reactive oxygen species production by establishing a feedback loop, and JA attenuated this cycle by reducing Et biosynthesis. In Bc[sup.+] + O[sub.3] [sup.+] leaves, Et peaked at 6 and 12 h FET, before SA confirmed a crosstalk between Et- and SA-related signaling pathways in lesion propagation. In O[sub.3] [sup.+] + Bc[sup.+] leaves, the H[sub.2]O[sub.2] induction triggered an accumulation of JA and Et, demonstrating a synergistic action in the regulation of defence reactions. The divergence in these profiles suggests a rather complex network of events in the transcriptional regulation of genes involved in the systemic acquired resistance.