Abstract
In plants, reactive oxygen species (ROS) associated with the response to pathogen attack are generated by NADPH oxidases or apoplastic peroxidases. Antisense expression of a heterologous French bean (Phaseolus vulgaris) peroxidase (FBP1) cDNA in Arabidopsis thaliana was previously shown to diminish the expression of two Arabidopsis peroxidases (peroxidase 33 [PRX33] and PRX34), block the oxidative burst in response to a fungal elicitor, and cause enhanced susceptibility to a broad range of fungal and bacterial pathogens. Here we show that mature leaves of T-DNA insertion lines with diminished expression of PRX33 and PRX34 exhibit reduced ROS and callose deposition in response to microbe-associated molecular patterns (MAMPs), including the synthetic peptides Flg22 and Elf26 corresponding to bacterial flagellin and elongation factor Tu, respectively. PRX33 and PRX34 knockdown lines also exhibited diminished activation of Flg22-activated genes after Flg22 treatment. These MAMP-activated genes were also downregulated in unchallenged leaves of the peroxidase knockdown lines, suggesting that a low level of apoplastic ROS production may be required to preprime basal resistance. Finally, the PRX33 knockdown line is more susceptible to Pseudomonas syringae than wild-type plants. In aggregate, these data demonstrate that the peroxidase-dependent oxidative burst plays an important role in Arabidopsis basal resistance mediated by the recognition of MAMPs.
Highlights
Plants have evolved sophisticated surveillance systems triggered by recognition of microbe-associated molecular patterns (MAMPs), molecules such as eubacterial flagellin or peptidoglycan (PGN) or fungal chitin, which plants use to identify the presence of potentially harmful microbes
We previously speculated that a peroxidase-generated oxidative burst may play an essential role in pattern-triggered immunity (PTI) as well as playing a role in activating NADPH oxidase during an effector-triggered hypersensitive response (HR) (Bindschedler et al, 2006)
The data presented in this article support this conclusion, showing that peroxidase knockdown lines are impaired in some key aspects of PTI
Summary
Plants have evolved sophisticated surveillance systems triggered by recognition of microbe-associated molecular patterns (MAMPs), molecules such as eubacterial flagellin or peptidoglycan (PGN) or fungal chitin, which plants use to identify the presence of potentially harmful microbes. The primary ROS studied to date include superoxide, hydrogen peroxide, and nitric oxide, which function either directly in the establishment of defense mechanisms or indirectly via synergistic interactions with other signaling molecules, such as salicylic acid (reviewed in Bolwell and Daudi, 2009). NADPH/NADH oxidases that generate superoxide, or cell walllocalized peroxidases that generate hydrogen peroxide, or both systems operating in tandem (Bolwell, 1999). To elucidate the underlying biochemical and physiological mechanisms involved in the plant defense response to pathogen attack, it is important to dissect the relative contributions of NADPH oxidases and peroxidases in the production of ROS in both basal resistance and in the so-called hypersensitive response (HR) The class of responses encompassing gene-forgene resistance and the hypersensitive response, collectively termed effector-triggered immunity (ETI), includes defenses activated by recognition of microbial virulence factors (effectors) that target PTI or other key host functions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
