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The involvement of glutathione (GSH) in plant defense against pathogen invasion is an established fact. However, the molecular mechanism conferring this tolerance remains to be explored. Here, proteomic analysis of pad2-1 , an Arabidopsis thaliana GSH-depleted mutant, in response to Pseudomonas syringae infection has been performed to explore the intricate position of GSH in defense against biotrophic pathogens. The pad2-1 mutant displayed severe susceptibility to P. syringae infection compared to the wild-type (Col-0) thus re-establishing a fundamental role of GSH in defense. Apart from general up-accumulation of energy metabolism-related protein-species in both infected Col-0 and pad2-1 , several crucial defense-related protein-species were identified to be differentially accumulated. Leucine-rich repeat-receptor kinase (LRR-RK) and nucleotide-binding site–leucine-rich repeat resistance protein (NBS–LRR), known to play a pioneering role against pathogen attack, were only weakly up-accumulated in pad2-1 after infection. Transcriptional and post-transcriptional regulators like MYB-P1 and glycine-rich repeat RNA-binding protein (GRP) and several other stress-related protein-species like heat shock protein 17 (HSP17) and glutathione-S-transferase (GST) were also identified to be differentially regulated in pad2-1 and Col-0 in response to infection. Together, the present investigation reveals that the optimum GSH-level is essential for the efficient activation of plant defense signaling cascades thus conferring resistance to pathogen invasion. [ABSTRACT FROM AUTHOR]

Abstract: Plant pathogenic fungi cause important yield losses in crops. A proteomic approach was used to study the changes in the leaf proteome profile of the plant Mentha arvensis infected with a necrotrophic fungus, Alternaria alternata. High-resolution two-dimensional gel electrophoresis (2-DE) followed by colloidal Coomassie staining and mass spectrometric analysis was used to identify highly abundant proteins differentially expressed in response to fungal infection. From a total of 210 reproducibly detected and analyzed spots, the intensity of sixty-seven spots was altered, and forty-five of them were successfully identified by matrix assisted laser desorption/ionization time of flight-mass spectrometry (MALDI TOF/TOF MS/MS). Fifty-six percent of the identified proteins belonged to energy and metabolism whereas 29% were stress and defense related. Taken together, the results allow to assess changes at the proteomic level in the host due to the defense response. Results show an initial defense response, not strong enough to overcome the pathogenesis, which may be similar to other susceptible plant–pathogen interactions; however, cross-talks between various defense pathways, regulatory networks and physiological conditions are other important aspects to be considered. [ABSTRACT FROM AUTHOR]

Abstract: The genus Mentha has been widely used in food, flavor, culinary, cosmetic and pharmaceutical industries. Substantial damage to this crop happened regularly due to environmental stresses like metal toxicity and pathogen attack. Here, an approach has been taken to raise transgenic mint over-expressing γ-glutamyl-cysteine synthetase (γ-ECS), the rate-limiting enzyme of GSH biosynthesis, resulted enhanced GSH content and its in planta expression confers significant tolerance towards abiotic/biotic stresses viz. metal toxicity — Cd, Zn as well as against infection of Alternaria alternata and Rhizoctonia solani. A differential proteomic analysis through 2-DE and MALDI TOF–TOF MSMS was performed to focus on the altered abundance of functionally important protein species in control and infected transgenic mint. Results showed a significant variation in the protein profile of the infected transgenic plant as compared to the wild/control transgenic counterpart. In addition to protein species related to stress and defense, redox regulation, transcription factors and energy & metabolism, protein species related to signaling and gene regulation as well as cell division also showed differential accumulation in infected transgenic. Hence, proteomics can be used as a tool to decipher the mechanism of action of GSH in providing tolerance against a necrotrophic fungus, A. alternata in transgenic mint. Biological significance: The reported work describes a comparative proteomics of non-model unsequenced plants like Mentha. There is a comparative protein profile between transgenic and its wild counterparts under control and infected condition. The work has an impact in crop proteomics and also tries to explain the application of proteomic approach to decipher the mechanism by which a foreign metabolite mediates stress tolerance in plant under control and infected condition. This article is part of a Special Issue entitled: Translational Plant Proteomics. [Copyright &y& Elsevier]