Abstract
Alterations in the proteome of Arabidopsis (Arabidopsis thaliana) leaves during responses to challenge by Pseudomonas syringae pv tomato DC3000 were analyzed using two-dimensional gel electrophoresis. Protein changes characteristic of the establishment of disease, basal resistance, and resistance-gene-mediated resistance were examined by comparing responses to DC3000, a hrp mutant, and DC3000 expressing avrRpm1, respectively. The abundance of each protein identified was compared with that of selected transcripts obtained from comparable GeneChip experiments. We report changes in three subcellular fractions: total soluble protein, chloroplast enriched, and mitochondria enriched over four time points (1.5-6 h after inoculation). In total, 73 differential spots representing 52 unique proteins were successfully identified. Many of the changes in protein spot density occurred before significant transcriptional reprogramming was evident between treatments. The high proportion of proteins represented by more than one spot indicated that many of the changes to the proteome can be attributed to posttranscriptional modifications. Proteins found to show significant change after bacterial challenge are representative of two main functional groups: defense-related antioxidants and metabolic enzymes. Significant changes to photosystem II and to components of the mitochondrial permeability transition were also identified. Rapid communication between organelles and regulation of primary metabolism through redox-mediated signaling are supported by our data.
Highlights
Alterations in the proteome of Arabidopsis (Arabidopsis thaliana) leaves during responses to challenge by Pseudomonas syringae pv tomato DC3000 were analyzed using two-dimensional gel electrophoresis
Pst DC3000 possesses up to 40 T3SSdelivered effector proteins that we describe as type 3 effectors (T3E), the majority are of unknown function and structure (Buell et al, 2003)
Many proteins that differentiated between treatments were identified in more than one spot, indicating probable posttranslational modification (PTM)
Summary
Alterations in the proteome of Arabidopsis (Arabidopsis thaliana) leaves during responses to challenge by Pseudomonas syringae pv tomato DC3000 were analyzed using two-dimensional gel electrophoresis. Proteins found to show significant change after bacterial challenge are representative of two main functional groups: defense-related antioxidants and metabolic enzymes. The HR is usually associated with rapid increases in cytosolic calcium, acidification of the apoplast, prolonged oxidative burst, changes in phosphorylation, and increases in nitric oxide (NO) These responses appear to be conserved; only the timing differs for each R-avr gene combination (Bennett et al, 2005). Cytosolic antioxidant enzymes are essential in controlling ROS generated by plant organelles (Davletova et al, 2005) Both chloroplasts and mitochondria are additional potential sources of ROS and possess well-developed mechanisms to rapidly detoxify free radicals. Changes to the proteome of chloroplasts are of particular interest because this organelle is implicated in the defense response in several ways. Photorespiration can modulate defense responses by dissipating excessive ROS, mitigating photooxidative damage (Zeier et al, 2004; Moreno et al, 2005)
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