Differential ozone sensitivity among Arabidopsis accessions and its relevance to ethylene synthesis

Abstract

We compared the physiological and molecular responses of two Arabidopsis accessions, Col-0 and Ws-2, to ozone (O 3 ) exposure. Observation of visible injury as well as ion-leakage analysis demonstrated clear differences between the O 3 -tolerant accession Col and the O 3 -sensitive accession Ws. RNA-blot analysis showed that O 3 -induced increases in mRNA levels of several ethylene-inducible genes and a salicylic acid-inducible gene were substantially higher in Ws than in Col. The time-course of induction of various mRNA levels shows that the expression of ethylene-inducible genes was rapidly, and more strongly, induced by O 3 in Ws than in Col, suggesting that Ws exhibits higher ethylenesignaling. Both the level of mRNA for an O 3 -inducible 1-aminocyclopropane-1-carboxylate synthase and the level of ethylene generation after 3 h of O 3 -exposure were higher in Ws than in Col. O 3 -induced leaf damage was attenuated by pretreatment with ethylene biosynthesis-and signaling-inhibitors, indicating that ethylene signaling is required for O 3 -induced leaf injury in Ws. On the other hand, an ethylene-overproducing mutant of Col, eto1-1, displayed significantly increased O 3 -in-duced leaf injury compared to wild type plants. These results indicate that the difference in O 3 sensitivity is dependent on the difference in ethylene production rate between these two accessions. Finally, we investigated the relationship between the degree of leaf damage and the level of ethylene evolution in 20 different Arabidopsis accessions. Based on the result, the accessions were classified into four types. However, most of them showed significant correlation between the ethylene production level and the degree of leaf injury, suggesting that ethylene signaling is an important factor in the natural variety of O 3 sensitivity among Arabidopsis accessions.

Analysis of oxidative signalling induced by ozone in Arabidopsis thaliana

“…Early induction of ethylene is an important marker of ozone sensitivity in plants and has been demonstrated in the Ws-0 plants (Mehlhorn & Wellburn 1987;Tamaoki et al 2003b). Many of the ethylene response genes involved in protein degradation pathway (Paepe et al 2004) were induced in response to ozone, suggesting that these genes may be mediated by increased ethylene.…”

“…In ozone-tolerant Col-0 plants, the regulation of many ozoneresponsive genes are ethylene and jasmonic acid (JA) dependent (Tamaoki et al 2003a). High ethylene levels in ozone-sensitive species like Ws-0 (Wellburn & Wellburn 1996;Tamaoki et al 2003b) can trigger the production of SA (Rao & Davis 1999) that in turn leads to increasing ROS and vice versa by a self-amplifying loop (Draper 1997;Van Camp, Van Montagu & Inze 1998), activating the oxidative cell death cycle (Van Camp, Van Montagu & Inze 1998;Overmyer et al 2003;Kangasjarvi et al 2005). SA signalling can promote ozone-induced cell death (Rao et al 2000;Tamaoki et al 2003a).…”

“…Arabidopsis ecotype Wassilewskija (Ws-0) is sensitive to ozone both in controlled environment chambers (Kanna et al . 2003;Tamaoki et al . 2003b) and in field conditions (Miyazaki et al .…”

Ethylene Supports Colonization of Plant Roots by the Mutualistic Fungus Piriformospora indica

“…MCP treatment was conducted immediately after inoculation of roots with P. indica . The final concentration of 1-MCP in the gas phase of the jar and petri dishes was expected to be about 500 ppt [54]. Roots were harvested at 3 and 7 dai, frozen in liquid nitrogen and subjected to DNA isolation (see below).…”

Increased Anion Channel Activity Is an Unavoidable Event in Ozone-Induced Programmed Cell Death

“…The production of ROS finally leads to a PCD characterized by the early release of cytochrome c from mitochondria, activation of proteases, DNA fragmentation, electrolyte leakage and ultrastructural changes characteristic of PCD [3], [4], [5], [10]. Responses that follow the O 3 challenge also include changes in gene expression and protein synthesis, and an accumulation of plant stress hormones, ethylene, salicylic acid (SA), abscisic acid (ABA) and jasmonic acid (JA) [4], [12], [13], [14], [15], [16], that regulate the induction and spreading of the oxidative stress symptoms [3], [14], [17], [18]. Treatment with O 3 also induces a rapid accumulation of NO, which could coincide with the formation of HR-like lesions, suggesting that NO is also an important signalling molecule in the plant response to O 3 [19].…”