Virus Diseases of Peanut

Plant proteomics update (2007-2008) : Second-generation proteomic techniques, an appropriate experimental design, and data analysis to fulfill MIAPE standards, increase plant proteome coverage and expand biological knowledge

Germin and germin-like proteins (GLPs) are encoded by a family of genes found in all plants. They are part of the cupin superfamily of biochemically diverse proteins, a superfamily that has a conserved tertiary structure, though with limited similarity in primary sequence. The subgroups of GLPs have different enzyme functions that include the two hydrogen peroxide-generating enzymes, oxalate oxidase (OxO) and superoxide dismutase. This review summarizes the sequence and structural details of GLPs and also discusses their evolutionary progression, particularly their amplification in gene number during the evolution of the land plants. In terms of function, the GLPs are known to be differentially expressed during specific periods of plant growth and development, a pattern of evolutionary subfunctionalization. They are also implicated in the response of plants to biotic (viruses, bacteria, mycorrhizae, fungi, insects, nematodes, and parasitic plants) and abiotic (salt, heat/cold, drought, nutrient, and metal) stress. Most detailed data come from studies of fungal pathogenesis in cereals. This involvement with the protection of plants from environmental stress of various types has led to numerous plant breeding studies that have found links between GLPs and QTLs for disease and stress resistance. In addition the OxO enzyme has considerable commercial significance, based principally on its use in the medical diagnosis of oxalate concentration in plasma and urine. Finally, this review provides information on the nutritional importance of these proteins in the human diet, as several members are known to be allergenic, a feature related to their thermal stability and evolutionary connection to the seed storage proteins, also members of the cupin superfamily.

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Germin and Germin-like Proteins: Evolution, Structure, and Function

Background
Members of plant WRKY transcription factor families are widely implicated in defense responses and various other physiological processes. For canola (Brassica napus L.), no WRKY genes have been described in detail. Because of the economic importance of this crop, and its evolutionary relationship to Arabidopsis thaliana, we sought to characterize a subset of canola WRKY genes in the context of pathogen and hormone responses.

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Identification and expression analysis of WRKY transcription factor genes in canola (Brassica napus L.) in response to fungal pathogens and hormone treatments.

Plant pathogenic fungi cause important yield losses in crops. In order to develop efficient and environmental friendly crop protection strategies, molecular studies of the fungal biological cycle, virulence factors, and interaction with its host are necessary. For that reason, several approaches have been performed using both classical genetic, cell biology, and biochemistry and the modern, holistic, and high-throughput, omic techniques. This work briefly overviews the tools available for studying Plant Pathogenic Fungi and is amply focused on MS-based Proteomics analysis, based on original papers published up to December 2009. At a methodological level, different steps in a proteomic workflow experiment are discussed. Separate sections are devoted to fungal descriptive (intracellular, subcellular, extracellular) and differential expression proteomics and interactomics. From the work published we can conclude that Proteomics, in combination with other techniques, constitutes a powerful tool for providing important information about pathogenicity and virulence factors, thus opening up new possibilities for crop disease diagnosis and crop protection.

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Proteomics of Plant Pathogenic Fungi

With the completion of genome projects for Arabidopsis thaliana, Oryza sativa and several other plant species, an increasing number of whole genome sequences are now available for plants. In this post-genomic era, a more thorough understanding of gene expression and function can be achieved through the characterization of the products of expression, the proteins, which are essential biological determinants of plant phenotypes. Proteomics offers a continually evolving set of novel techniques to study all facets of protein structure and function. The application of proteomics in plant pathology is becoming more commonplace with techniques such as two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS) being used to characterize cellular and extracellular virulence and pathogenicity factors produced by pathogens as well as to identify changes in protein levels in plant hosts upon infection by pathogenic organisms and symbiotic counterparts. This review article summarizes the current status of geland non gel-based proteomic techniques and describes the significant discoveries that have resulted from the various proteome-level investigations into phytopathogenic microorganisms and plant host-microbe interactions.

Application of Proteomics to Investigate Plant-Microbe Interactions

Proteome-level changes in two Brassica napus lines exhibiting differential responses to the fungal pathogen Alternaria brassicae

To better understand the pathogen-stress response of Brassica species against the ubiquitous hemi-biotroph fungus Leptosphaeria maculans, we conducted a comparative proteomic analysis between blackleg-susceptible Brassica napus and blackleg-resistant Brassica carinata following pathogen inoculation. We examined temporal changes (6, 12, 24, 48 and 72 h) in protein profiles of both species subjected to pathogen-challenge using two-dimensional gel electrophoresis. A total of 64 proteins were found to be significantly affected by the pathogen in the two species, out of which 51 protein spots were identified using tandem mass spectrometry. The proteins identified included antioxidant enzymes, photosynthetic and metabolic enzymes, and those involved in protein processing and signaling. Specifically, we observed that in the tolerant B. carinata, enzymes involved in the detoxification of free radicals increased in response to the pathogen whereas no such increase was observed in the susceptible B. napus. The expression of genes encoding four selected proteins was validated using quantitative real-time PCR and an additional one by Western blotting. Our findings are discussed with respect to tolerance or susceptibility of these species to the pathogen.

Towards identifying Brassica proteins involved in mediating resistance to Leptosphaeria maculans: A proteomics‐based approach

Blackleg and blackspot are economically important diseases of canola caused by Leptosphaeria maculans and Alternaria brassicae, respectively, and can lead to significant crop losses. In this study, we investigated the effects of cytokinins on the symptoms caused by these two pathogens. We observed that cytokinin, especially 6-benzyl amino purine, was able to significantly reduce disease symptoms and mycelial growth within plant tissues. This cytokinin was also able to inhibit the in vitro growth of both fungi. Other cytokinins such as kinetin or adenine hemisulfate were unable to inhibit fungal growth in vitro, suggesting that the presence of a benzene ring structure is required for the inhibitory effects observed. Our findings are discussed within the context of plant–pathogen interactions.

Cytokinin inhibits the growth of Leptosphaeria maculans and Alternaria brassicae

Brassica napus (canola) is an important oilseed crop in many countries throughout the world including Canada. One of the major constraints on canola productivity is blackspot disease caused by the necrotrophic phytopathogenic fungus Alternaria brassicae. Two isolates of A. brassicae with significant differences in virulence have been characterized at the proteomelevel. The morphological observations indicated the Ontario isolate to be more virulent by virtue of increased disease severity score as compared to the UAMH7476 isolate. This was further confirmed through histological observations that indicated extensive colonization of the host tissue by the highly virulent isolate. Mycelial protein profiles of two differentially virulent A. brassicae isolates were compared using two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS) in order to identify proteins that may be responsible for the observed differences. The investigation suggested several differences in the mycelial proteomes of the two isolates. The proteins that were significantly abundant in the more virulent isolate included a protein with conserved actin related protein 2/3 domain, enolase, malate dehydrogenase and serine protease. These results suggest that the differential protein expression pattern could be exploited to identify putative virulence and pathogenicity factors in A. brassicae.

Nidhi Sharma

Papers

Application of Proteomics to Investigate Plant-Microbe Interactions

Proteome-level changes in two Brassica napus lines exhibiting differential responses to the fungal pathogen Alternaria brassicae

Towards identifying Brassica proteins involved in mediating resistance to Leptosphaeria maculans: A proteomics‐based approach

Cytokinin inhibits the growth of Leptosphaeria maculans and Alternaria brassicae

A Possible Proteome-level Explanation for Differences in Virulence of Two Isolates of a Fungal Pathogen Alternaria brassicae