Similar foliar lesions but opposite hormonal patterns in a tomato mutant impaired in ethylene perception and its near isogenic wild type challenged with ozone

Abstract

The accumulation of ethylene (ET), hydrogen peroxide (H 2O 2), nitric oxide (NO), salicylic (SA) and jasmonic (JA) acids, as well as the transcriptional activation of JA-biosynthetic and hypersensitive response (HR) marker genes were examined in ET-insensitive Never ripe ( Nr) mutant of tomato ( Lycopersicon esculentum L.) and in its near isogenic wild type (WT, cv. New Yorker) during and after an acute ozone (O 3) fumigation. The scoring of O 3-induced foliar symptoms indicated similar sensitivity between WT and Nr. In both genotypes the O 3-induced ET emission peaked after 3 h of fumigation, although with different intensities between them; H 2O 2 and NO bursts occurred, both showing a biphasic time course. However, SA and JA revealed opposite accumulation patterns: in Nr a high level of SA but a low JA accumulation were observed, whereas in WT a marked evolution of JA but a weak SA accumulation were detected. The transcription of certain JA-biosynthetic and HR-inducible genes was similarly activated by O 3 in the two tomato lines. According to the current models on the molecular events leading to the development of O 3-induced foliar symptoms, here we suggest that the partial ET-insensitivity of Nr would have promoted a SA build-up, leading to cell death and to a reduced JA accumulation. In WT the O 3-induced leaf injury without SA build-up but with JA accumulation would have arisen from the perception of high ET and H 2O 2 levels.