ASPARTATE OXIDASE Plays an Important Role in Arabidopsis Stomatal Immunity

Perception of pathogen-associated molecular patterns (PAMPs), such as bacterial flagellin (or the peptide flg22), by surface-localized receptors activates defense responses and subsequent immunity. In a previous forward-genetic screen aimed at the identification of Arabidopsis (Arabidopsis thaliana)...

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Published in:Plant physiology (Bethesda) 2012-08, Vol.159 (4), p.1845-1856
Main Authors: Macho, Alberto P., Boutrot, Freddy, Rathjen, John P., Zipfel, Cyril
Format: Article
Language:English
Subjects:
Abscisic Acid - pharmacology
Amino Acid Oxidoreductases - metabolism
Arabidopsis - enzymology
Arabidopsis - immunology
Arabidopsis - microbiology
Arabidopsis - physiology
Arabidopsis Proteins - metabolism
Biological and medical sciences
Biosynthesis
Chitin - pharmacology
Flagellin - pharmacology
Fundamental and applied biological sciences. Psychology
Genes, Plant - genetics
Immunity
Mutagenesis, Insertional - genetics
Mutation - genetics
NADPH Oxidases - metabolism
Niacin - pharmacology
Oxidases
Pathogens
Plant immunity
Plant Immunity - immunology
Plant physiology and development
Plant Roots - drug effects
Plant Roots - enzymology
Plant Roots - growth & development
Plant Stomata - drug effects
Plant Stomata - immunology
Plant Stomata - microbiology
Plant Stomata - physiology
Plants
PLANTS INTERACTING WITH OTHER ORGANISMS
Pseudomonas syringae - drug effects
Pseudomonas syringae - physiology
Reactive oxygen species
Reactive Oxygen Species - metabolism
Receptors
Receptors, Pattern Recognition - metabolism
Root hairs
Seedlings
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Summary:Perception of pathogen-associated molecular patterns (PAMPs), such as bacterial flagellin (or the peptide flg22), by surface-localized receptors activates defense responses and subsequent immunity. In a previous forward-genetic screen aimed at the identification of Arabidopsis (Arabidopsis thaliana) flagellin-insensitive (fin) mutants, we isolated fin4, which is severely affected in flg22-triggered reactive oxygen species (ROS) bursts. Here, we report that FIN4 encodes the chloroplastic enzyme ASPARTATE OXIDASE (AO), which catalyzes the first irreversible step in the de novo biosynthesis of NAD. Genetic studies on the role of NAD have been hindered so far by the lethality of null mutants in NAD biosynthetic enzymes. Using newly identified knockdown fin alleles, we found that AO is required for the ROS burst mediated by the NADPH oxidase RBOHD triggered by the perception of several unrelated PAMPs. AO is also required for RBOHD-dependent stomatal closure. However, full AO activity is not required for flg22-induced responses that are RBOHD independent. Interestingly, although the fin4 mutation dramatically affects RBOHD function, it does not affect functions carried out by other members of the RBOH family, such as RBOHC and RBOHF. Finally, we determined that AO is required for stomatal immunity against the bacterium Pseudomonas syringae. Altogether, our work reveals a novel specific requirement for AO activity in PAMP-triggered RBOHD-dependent ROS burst and stomatal immunity. In addition, the availability of viable mutants for the chloroplastic enzyme AO will enable future detailed studies on the role of NAD metabolism in different cellular processes, including immunity, in Arabidopsis.
ISSN:0032-0889
1532-2548
1532-2548
DOI:10.1104/pp.112.199810