Induction of some defense-related genes and oxidative burst is required for the establishment of systemic acquired resistance in Capsicum annuum

Abstract

The inoculation of primary pepper leaves with an avirulent strain of Xanthomonas campestris pv. vesicatoria induced systemic acquired resistance (SAR) in the non-inoculated, secondary leaves. This SAR response was accompanied by the systemic expression of the defense-related genes, a systemic microoxidative burst generating H2O2, and the systemic induction of both ion-leakage and callose deposition in the non-inoculated, secondary leaves. Some defense-related genes including those encoding PR-1, chitinase, osmotin, peroxidase, PR10, thionin, and SAR8.2 were markedly induced in the systemic leaves. The conspicuous systemic accumulation of H2O2 and the strong increase in peroxidase activity in the pepper leaves was suggested to play a role in the cell death process in the systemic micro-hypersensitive responses (HR), leading to the induction of the SAR. Treatment of the primary leaves with diphenylene iodinium (DPI), an inhibitor of oxidative burst, substantially reduced the induction of some of the defense-related genes, and lowered the activation of the oxidative bursts in the systemic leaves distant from the site of the avirulent pathogen inoculation and subsequently SAR. Overall, these results suggest that the induction of some defense-related genes as well as a rapid increase in oxidative burst is essential for establishing SAR in pepper plants.

Involvement of the Pepper Antimicrobial Protein CaAMP1 Gene in Broad Spectrum Disease Resistance

“…The induced resistance response of plants to diseases correlates intimately with the accumulation of PR proteins. A number of signaling molecules, including salicylic acid (SA), ethylene, and jasmonic acid (JA), have been shown to amplify and regulate defense responses in plants during initial activation events, such as oxidative bursts or the expression of PR genes (Johnson et al, 2003;Schenk et al, 2003;Lee and Hwang, 2005).…”

The Pepper E3 Ubiquitin Ligase RING1 Gene,CaRING1, Is Required for Cell Death and the Salicylic Acid-Dependent Defense Response

“…8). These enhanced defense responses may be activated by various signal transduction pathways, which can be modulated by plant hormones such as SA and JA/ethylene (Lee and Hwang, 2005;Pieterse et al, 2009;. In Arabidopsis, AtPR1 induction depends upon the SAdependent pathway (Glazebrook et al, 1996;Rogers and Ausubel, 1997), whereas AtPDF1.2 is a JA/ethyleneresponsive marker (Penninckx et al, 1998).…”

Induced Resistance to Powdery Mildew by 2,6-Dichloroisonicotinic Acid is Associated with Activation of Active Oxygen Species-mediated Enzymes in Cucumber Plants

“…This result suggested that AOS acts as a signal factor for the expression of β-1,3-glucanase in cucumber leaves. Lee and Hwang (2005) reported that the co-infiltration of DPI with a virulent pathogen markedly inhibited POD activity as well as H 2 O 2 accumulation. They concluded that the reduction of the H 2 O 2 levels, as a result of DPI application, suppressed the transcription of defense-related genes.…”

“…It has been well documented that the development of SAR systems in plants was associated with an oxidative burst, such as the generation of superoxide and subsequent accumulation of H 2 O 2 (Alvarez et al, 1998). It is not yet known whether H 2 O 2 is the primary signal mediator or whether its interactions with other intermediates such as SA and jasmonic acid induce the SAR genes (Lee and Hwang, 2005 Although foliar application of exogenous H 2 O 2 does not play to induce β-1,3-glucanase, it was affects on the activation of AOS-mediated enzymes and restriction of powdery mildew infection. The reduction of effectiveness of restriction of powdery mildew by inhibitor of oxidative burst may reflect the critical role of AOS in contributing to the antifungal activity by activation of AOS-mediated enzymes.…”