Study : Primed primary metabolism in systemic leaves: a functional systems analysis


Primed primary metabolism in systemic leaves: a functional systems analysis
During their co-evolution, plants have learned to counteract bacterial infection by preparing yet uninfected tissues for an enhanced defence response, the so-called systemic acquired resistance or priming response. Primed leaves express a wide range of genes that enhance the defence response once an infection takes place. While hormone-driven defence signalling and generation of defensive metabolites has been well studied, less focus has been set on the reorganization of primary metabolism in systemic leaves. Since primary metabolism plays an essential role for fuelling and optimizing defences in terms of providing energy and chemical building blocks, we investigated medium-term primed changes in primary metabolism at RNA and metabolite levels in systemic leaves of Arabidopsis thaliana plants that were locally infected with Pseudomonas syringae. While known defence genes were still activated 3-4 days after infection, we also found several parts of primary metabolism to be significantly altered. Nitrogen (N)-metabolism and content of amino acids and other N-containing metabolites were significantly reduced, whereas the organic acids fumarate and malate were strongly increased. We suggest that reduction of N-metabolites in systemic, yet non-infected leaves primes defence against bacterial infection by reducing the nutritional value of systemic tissue. The increased organic acids serve as a quickly available metabolic resource of energy and carbon-building blocks for the production of defence metabolites during subsequent secondary infections. Overall design: Transcriptome profiling by RNA-sequencing of 18 systemic leaf samples from Arabidopsis thaliana Col-0 treated with P. syringae or mock.


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