Peroxidase‐dependent apoplastic oxidative burst in Arabidopsis required for pathogen resistance

Abstract

SummaryThe oxidative burst is an early response to pathogen attack leading to the production of reactive oxygen species (ROS) including hydrogen peroxide. Two major mechanisms involving either NADPH oxidases or peroxidases that may exist singly or in combination in different plant species have been proposed for the generation of ROS. We identified an Arabidopsis thaliana azide-sensitive but diphenylene iodoniuminsensitive apoplastic oxidative burst that generates H 2 O 2 in response to a Fusarium oxysporum cell-wall preparation. Transgenic Arabidopsis plants expressing an anti-sense cDNA encoding a type III peroxidase, French bean peroxidase type 1 (FBP1) exhibited an impaired oxidative burst and were more susceptible than wild-type plants to both fungal and bacterial pathogens. Transcriptional profiling and RT-PCR analysis showed that the anti-sense (FBP1) transgenic plants had reduced levels of specific peroxidase-encoding mRNAs, including mRNAs corresponding to Arabidopsis genes At3g49120 (AtPCb) and At3g49110 (AtPCa) that encode two class III peroxidases with a high degree of homology to FBP1. These data indicate that peroxidases play a significant role in generating H 2 O 2 during the Arabidopsis defense response and in conferring resistance to a wide range of pathogens.

Reactive oxygen species and plant resistance to fungal pathogens

“…ROS formation dependent on an apoplastic peroxidase was later confirmed in other plants (bean, Arabidopsis, pepper, lettuce, cotton) (Bestwick et al, 1998;Bindschedler et al, 2006;Bolwell, 1999;Choi et al, 2007;Martinez et al, 1998). The relevance of apoplastic peroxidase was explored in A. thaliana expressing an antisense construct of the heme-containing cell-wall-bound class III peroxidase FBP1 of French bean.…”

“…In such antisense plants the DPIinsensitive oxidative burst was decreased in response to cell wall preparations of Fusarium oxysporum. The antisense plants displayed enhanced susceptibility to a broad range of fungal and bacterial pathogens and showed a decrease in expression of mRNAs coding for peroxidase AtPCa (PRX33) and AtPCb (PRX34) (Bindschedler et al, 2006). When Arabidopsis tissue culture lines generated from FBP1 antisense plants are treated with ROS inhibitors (azide and DPI) about half of the MAMP-induced H 2 O 2 can be accounted for by a peroxidase-generated reaction while the rest is likely to depend on NADPH oxidases and other sources.…”

An anionic class III peroxidase from zucchini may regulate hypocotyl elongation through its auxin oxidase activity

“…The antisens strategy is known to be unspeciWc. For example A. thaliana plants expressing the heterologous French bean peroxidase type 1 (FBP1) resulted in the silencing of at least two endogenous isoforms in leaves (Bindschedler et al 2006). Because peroxidase gene sequences contain highly conserved domain, it is highly probable that the silencing of APRX in A. thaliana also aVected the transcription of other Arabidopsis peroxidases involved in auxin catabolism and therefore result in a higher endogenous auxin content in S-APRX seedlings.…”

“…Nevertheless, auxin levels were not aVected in the overexpressing transgenic plants (Lagrimini et al 1997b) and the protein was not considered as having a role in auxin catabolism anymore (Dowd and Lagrimini 2006). The generation of transgenic plants with diVerent features has been performed in attempt to identify the function of speciWc peroxidase isoforms (Heggie et al 2005;Bindschedler et al 2006). However, to our knowledge, amongst the many peroxidases expressed in plants, no studies have unambiguously shown until now a particular isozyme to be both in vitro and in planta speciWcally involved in auxin catabolism or another speciWc mechanism.…”

“…In an attempt to identify the function of speciWc isoforms, several authors reported the generation of transgenic plants with diVerent features (Heggie et al 2005;Bindschedler et al 2006). Nevertheless, although in some cases spatial and temporal localization or indirect evidence might indicate their involvement in speciWc mechanisms (Ostergaard et al 2000;Jansen et al 2001), the in planta function of a single isoform has never been clearly characterized.…”