Jasmonic Acid Signaling Modulates Ozone-Induced Hypersensitive Cell Death

Abstract

INTRODUCTIONPlants continuously produce active oxygen species (AOS) such as superoxide radical ( • O 2 Ϫ ), hydrogen peroxide (H 2 O 2 ), and singlet oxygen ( 1 O 2 ) as a consequence of normal cellular metabolism. Under normal conditions, plants rapidly metabolize these AOS with the help of constitutive antioxidant enzymes or metabolites (Scandalios, 1997). However, when subjected to environmental stresses such as cold, high light, ozone (O 3 ), pathogens, and UV irradiation, excess AOS is generated. This increase in AOS production necessitates the activation of additional defenses (Doke, 1997;Scandalios, 1997). Unless these AOS are efficiently metabolized, they rapidly oxidize and damage membrane lipids, proteins, and other cellular components. This leads to cellular dysfunction and can ultimately cause cell death, which is manifested by the appearance of necrotic lesions (Mudd, 1997). Based on the assumption that AOS are highly reactive and lead to cellular dysfunction, AOS generation is frequently considered deleterious and harmful. However, recent studies have demonstrated that AOS are important components of signaling pathways that influence plant defense responses, including cell death (Jabs et al., 1996;Alvarez et al., 1998;Karpinski et al., 1999;Solomon et al., 1999).H 2 O 2 and • O 2 Ϫ have been implicated as signal molecules that can activate defense responses. Treating cell cultures with H 2 O 2 alone induces defense responses and cell death (Levine et al., 1994;Solomon et al., 1999). However, although sublethal H 2 O 2 concentrations induce expression of defense genes, complete induction of defense genes and cell death requires additional signaling molecules such as salicylic acid (SA) at the whole-plant level (Chamnongpol et al., 1998;Rao and Davis, 1999). These studies have established that AOS probably require additional downstream components to transduce or amplify the signal Bolwell, 1999). Among several molecules proposed to act downstream of AOS, SA, jasmonic acid (JA), and ethylene are considered major regulators of plant defense responses (Dong, 1998;Glazebrook, 1999). SA is one of the most widely studied stress-signaling molecules; its role in influencing plant resistance to pathogens and other stress factors is well documented (Draper, 1997;Shirasu et al., 1997;Surplus et al., 1998;Rao and Davis, 1999). Similar to SA, JA also is believed to play an important role in influencing plant resistance to pathogens and other stress factors (Creelman and Mullet, 1997;Penninckx et al., 1998;Vijayan et al., 1998). The recent cloning of COI1 has increased our understanding of the involvement of protein degradation in JA-induced responses (Xie et al., 1998); however, little is 1 Current address: Paradigm Genetics, Inc., 104 Alexander Drive, Research Triangle Park, NC 27709. 2 Current address: Mendel Biotechnology, Inc., 21375 Cabot Boulevard, Hayward, CA 94545. 3 To whom correspondence should be addressed. E-mail kdavis @paragen.com; fax 919-572-6764. 1634The Plant Cell known about other potential m...

(Z)-3-Hexenol induces defense genes and downstream metabolites in maize

“…2,5). Since the JA and SA defense pathways can respond antagonistically (Doares et al 1995;Rao et al 2000), an elevated level of applied MeJA may play some role in the down-regulation of MeSA emissions as well as endogenous SA levels.…”

Jasmonate-related mutants of Arabidopsis as tools for studying stress signaling

“…Endogenous JA levels and AOS-mRNA levels increase after ozone treatment (Rao et al 2000). In addition, pretreatment with methyl jasmonate decreases lesion formation in the ozone-sensitive ecotype Cvi and in the ozone-sensitive mutant rcd1 (Overmyer et al 2000;Rao et al 2000). Cvi, but not rcd1 was found to be insensitive to JAs and, vice versa, the JA-insensitive/ biosynthetic mutants jar1, coi1 and fad3-2fad7-1fad8 were found to be ozone sensitive (Overmyer et al 2000;Rao et al 2000).…”

“…Recently it has become evident that JAs also play an important role in the ozone response. Endogenous JA levels and AOS-mRNA levels increase after ozone treatment (Rao et al 2000). In addition, pretreatment with methyl jasmonate decreases lesion formation in the ozone-sensitive ecotype Cvi and in the ozone-sensitive mutant rcd1 (Overmyer et al 2000;Rao et al 2000).…”

“…Levels of endogenous JAs are highest in young, growing tissue and increase after treatment of cell cultures with elicitors or after subjecting plants to wounding, UV light, water deficit, pathogens and ozone (Conconi et al 1996;Creelman and Mullet 1997;Rao et al 2000). The application of exogenous JAs induces the expression of a variety of genes that are also responsive to other stresses such as wounding and pathogen infection.…”

New stereoisomeric derivatives of jasmonic acid generated by biotransformation with the fungus Gibberella fujikuroi affect the viability of human cancer cells

“…Jasmonates, their precursors, or their metabolites, are known to accumulate in higher plants (Wasternack, 2007) and fungi (Miersch et al 1999a). These molecules, ubiquitous in the plant kingdom, constitute a group of bioactive fatty acid derivatives that perform several important roles in growth, development, as well as biotic and abiotic stress (Rao et al 2000;Dombrowski, 2003;Stratmann, 2003;Shan et al 2007;Wasternack, 2007;Herman et al 2008). Furthermore, their role in regulating defense responses against herbivore attack and infection by some pathogens has been extensively studied (Creelman and Mullet, 1997;Kessler and Baldwin, 2002;Li, et al 2002;Wasternack and Hause, 2002;Rotem et al 2003;Turner et al 2004;Wasternack, 2007;Browse and Howe, 2008;Miersch et al 2008;Browse, 2009).…”