Abstract
Industrial activities have caused tropospheric CO2 concentrations to increase over the last two centuries, a trend that is predicted to continue for at least the next several decades. Here, we report that growth of plants in a CO2-enriched environment activates responses that are central to defense against pathogenic attack. Salicylic acid accumulation was triggered by high-growth CO2 in Arabidopsis (Arabidopsis thaliana) and other plants such as bean (Phaseolus vulgaris). A detailed analysis in Arabidopsis revealed that elevated CO2 primes multiple defense pathways, leading to increased resistance to bacterial and fungal challenge. Analysis of gene-specific mutants provided no evidence that activation of plant defense pathways by high CO2 was caused by stomatal closure. Rather, the activation is partly linked to metabolic effects involving redox signaling. In support of this, genetic modification of redox components (glutathione contents and NADPH-generating enzymes) prevents full priming of the salicylic acid pathway and associated resistance by high CO2 The data point to a particularly influential role for the nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase, a cytosolic enzyme whose role in plants remains unclear. Our observations add new information on relationships between high CO2 and oxidative signaling and provide novel insight into plant stress responses in conditions of increased CO2.
Highlights
Industrial activities have caused tropospheric CO2 concentrations to increase over the last two centuries, a trend that is predicted to continue for at least the several decades
Because SA is an important compound in plant responses to pathogens, we quantified the effect of 1,000 mL L21 CO2 on this compound in Arabidopsis and three selected crop species growing in the absence of biotic challenge
To enable the use of genespecific mutants to elucidate the processes underlying the increases in SA, we focused the rest of the study on the Arabidopsis Col-0 background
Summary
Industrial activities have caused tropospheric CO2 concentrations to increase over the last two centuries, a trend that is predicted to continue for at least the several decades. Our observations add new information on relationships between high CO2 and oxidative signaling and provide novel insight into plant stress responses in conditions of increased CO2 Plants elaborate their cellular matter by generating carbon skeletons from atmospheric CO2, the substrate for photosynthesis. The question has received attention for many years (Manning and von Tiedemann, 1995), information on the potential impact of increased CO2 on plant susceptibility to pathogen attack remains fragmentary Both positive and negative effects of increased CO2 on plant susceptibility to disease have been reported (McElrone et al, 2005; Lake and Wade, 2009; Melloy et al, 2010; Eastburn et al, 2011; Pangga et al, 2011). The effects of high CO2 on primary metabolic pathways could feed forward to modify the production of defense compounds
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