Impact of high atmospheric carbon dioxide on the biotic stress response of the model cereal species Brachypodium distachyon

Losses due to disease and climate change are among the most important issues currently facing crop production. It is therefore important to establish the impact of climate change, and particularly of high carbon dioxide (hCO2), on plant immunity in cereals, which provide 60% of human calories. The aim of this study was to determine if hCO2 impacts Brachypodium distachyon immunity, a model plant for temperate cereals. Plants were grown in air (430 ppm CO2) and at two high CO2 conditions, one that is relevant to projections within the coming century (1000 ppm) and a concentration sufficient to saturate photosynthesis (3000 ppm). The following measurements were performed: phenotyping and growth, salicylic acid contents, pathogen resistance tests, and RNAseq analysis of the transcriptome. Improved shoot development was observed at both 1000 and 3000 ppm. A transcriptomic analysis pointed to an increase in primary metabolism capacity under hCO2. Alongside this effect, up-regulation of genes associated with secondary metabolism was also observed. This effect was especially evident for the terpenoid and phenylpropanoid pathways, and was accompanied by enhanced expression of immunity-related genes and accumulation of salicylic acid. Pathogen tests using the fungus Magnaporthe oryzae revealed that hCO2 had a complex effect, with enhanced susceptibility to infection but no increase in fungal development. The study reveals that immunity in B. distachyon is modulated by growth at hCO2 and allows identification of pathways that might play a role in this effect

Metabolite modification in oxidative stress responses: A case study of two defense hormones

Studies of the Arabidopsis cat2 mutant lacking the major leaf isoform of catalase have allowed the potential impact of intracellular H2O2 on plant function to be studied. Here, we report a robust analysis of modified gene expression associated with key families involved in metabolite modification in cat2. Through a combined transcriptomic and metabolomic analysis focused on the salicylic acid (SA) and jasmonic acid (JA) pathways, we report key features of the metabolic signatures linked to oxidative stress-induced signaling via these defence hormones and discuss the enzymes that are likely to be involved in determining these features. We provide evidence that specific UDP-glycosyl transferases contribute to the glucosylation of SA that accumulates as a result of oxidative stress in cat2. Glycosides of dihydroxybenzoic acids that accumulate alongside SA in cat2 are identified and, based on the expression of candidate genes, likely routes for their production are discussed. We also report that enhanced intracellular H2O2 triggers induction of genes encoding different enzymes that can metabolize JA. Integrated analysis of metabolite and transcript profiles suggests that a gene network involving specific hydrolases, hydroxylases, and sulfotransferases functions to limit accumulation of the most active jasmonates during oxidative stress

Impact of high atmospheric carbon dioxide on the biotic stress response of the model cereal species Brachypodium distachyon

International audienceLosses due to disease and climate change are among the most important issues currently facing crop production. It is therefore important to establish the impact of climate change, and particularly of high carbon dioxide (hCO 2 ), on plant immunity in cereals, which provide 60% of human calories. The aim of this study was to determine if hCO 2 impacts Brachypodium distachyon immunity, a model plant for temperate cereals. Plants were grown in air (430 ppm CO 2 ) and at two high CO 2 conditions, one that is relevant to projections within the coming century (1000 ppm) and a concentration sufficient to saturate photosynthesis (3000 ppm). The following measurements were performed: phenotyping and growth, salicylic acid contents, pathogen resistance tests, and RNAseq analysis of the transcriptome. Improved shoot development was observed at both 1000 and 3000 ppm. A transcriptomic analysis pointed to an increase in primary metabolism capacity under hCO 2 . Alongside this effect, up-regulation of genes associated with secondary metabolism was also observed. This effect was especially evident for the terpenoid and phenylpropanoid pathways, and was accompanied by enhanced expression of immunity-related genes and accumulation of salicylic acid. Pathogen tests using the fungus Magnaporthe oryzae revealed that hCO 2 had a complex effect, with enhanced susceptibility to infection but no increase in fungal development. The study reveals that immunity in B. distachyon is modulated by growth at hCO 2 and allows identification of pathways that might play a role in this effect