Abstract
Unlike mammals with adaptive immunity, plants rely on their innate immunity based on pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) for pathogen defense. Reactive oxygen species, known to play crucial roles in PTI and ETI, can perturb cellular redox homeostasis and lead to changes of redox-sensitive proteins through modification of cysteine sulfhydryl groups. Although redox regulation of protein functions has emerged as an important mechanism in several biological processes, little is known about redox proteins and how they function in PTI and ETI. In this study, cysTMT proteomics technology was used to identify similarities and differences of protein redox modifications in tomato resistant (PtoR) and susceptible (prf3) genotypes in response to Pseudomonas syringae pv tomato (Pst) infection. In addition, the results of the redox changes were compared and corrected with the protein level changes. A total of 90 potential redox-regulated proteins were identified with functions in carbohydrate and energy metabolism, biosynthesis of cysteine, sucrose and brassinosteroid, cell wall biogenesis, polysaccharide/starch biosynthesis, cuticle development, lipid metabolism, proteolysis, tricarboxylic acid cycle, protein targeting to vacuole, and oxidation–reduction. This inventory of previously unknown protein redox switches in tomato pathogen defense lays a foundation for future research toward understanding the biological significance of protein redox modifications in plant defense responses.
Highlights
Pseudomonas syringae, a hemibiotrophic bacterial pathogen, causes bacterial speck disease in a wide range of plant species, including crops such as tomato (Solanum lycopersicum) and the reference plant Arabidopsis thaliana
post-translational modifications (PTMs) of proteins may function as molecular switches to turn on or off signaling and/or metabolic processes in plant response to external stimuli.[7,8,9]. Both pathogen-associated molecular patterns (PAMPs)-triggered immunity (PTI) and effector-triggered immunity (ETI) responses lead to increases in reactive oxygen species (ROS) production.[4,10,11]
Identification of redox-responsive cysteines, peptides, and proteins Redox proteomics approaches are based on differential labeling of redox-modified cysteines in proteins and have shown utility in unraveling important biological mechanisms
Summary
Pseudomonas syringae, a hemibiotrophic bacterial pathogen, causes bacterial speck disease in a wide range of plant species, including crops such as tomato (Solanum lycopersicum) and the reference plant Arabidopsis thaliana. Plant–pathogen interactions involve sophisticated molecular interplay underlying an evolutionary arms race.[3] Plants are able to recognize pathogens through pathogen-associated molecular patterns (PAMPs). This response and subsequent changes within the plant cells are often called PAMP-triggered immunity (PTI). The microbe recognition is achieved by plasma membrane pattern recognition receptors, which are leucine-rich receptor-like kinases or receptor-like proteins.[4] After PAMP recognition, plant cells undergo alkalization, change in ion flux, increase in reactive oxygen species (ROS), and activation of mitogen-activated protein kinase cascade.[5] Bypassing or suppressing these responses benefits the bacteria. Through a type III secretion system, the bacteria can inject effector proteins (T3Es) into the host cells to attenuate PTI
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