Plant Resistance: Antioxidant Perspective View of Plant-Fungal Pathogen Interactions

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One of the most rapid plant defense reactions after pathogen attack is the so-called oxidative burst, which constitutes the production of reactive oxygen species (ROS) at the site of attempted invasion. Vitamin B6 (VB6), an essential cofactor for numerous metabolic enzymes, is a potent antioxidant and plays important roles in developmental process and plant stress responses. However, little is known about its function in plant disease resistance response against soilborne pathogen infections. Brachypodium distachyon (Bd) is now established as the model system for grass genomics and gene discovery and is increasingly used as the model for cereal diseases. Rhizoctonia solani AG-8 causes rhizoctonia root rot and pre-emergence damping-off (aka barepatch) of wheat and barely, two major yield-limiting diseases in cereal production regions worldwide. All known cultivars of wheat and barley, including those having resistance to rusts and other pathogens, are susceptible to R. solani AG-8 and lack of control of Rhizoctonia poses a major barrier to the widespread adoption of direct seeding. Brachypodium lines are infected by the soilborne plant pathogen R. solani AG-8, and develop similar symptoms to the crop host (wheat). Thus, the study of enhanced VB6 lines of Brachypodium-R. solani interactions holds promise to improve our understanding of disease resistance and hence generation of R. solani resistant lines. In the present proposal we explore the involvement of VB6 in defense response against the R. solani through functional analysis of VB6 biosynthetic genes in Bd lines. The proposal will provide insight into the effect of the VB6 on plant response to pathogens and its role as an antioxidant, and also to understand the role of VB6 in the protection of the pathogen against oxidative stress. Approach: Bd transgenic lines over expressing (OX) or down-regulating (knockdown; KD) VB6 genes followed by a series of experiments will be generated in order to provide evidence that enhanced vitamin B6 content in OX lines have increased tolerance to oxidative stress and are less susceptible than KD and WT lines to R. solani infections or to paraquat (ROS inducer). Also, we will explore how whole-cellular processes at the transcriptome and metabolome levels are affected since broad changes of the primary metabolism of Bd lines with enhanced or reduced VB6 genes are anticipated. Expected significance: Finding quantitative variation in resistance to R. solani in Bd plants over expressing VB6 encoding genes would allow selection of resistant lines. The generation of crops combining enhanced levels of bioavailable VB6 vitamers and better generic traits such as tolerance to oxidative stress caused by fungal pathogens represent a valuable tool to improve nutrition and food security. HQP training: 5 graduate students and a PDF will be trained in omics' disciplines, bioinformatics and molecular plant pathology