2 on plants, but its potential impact on inducible plant defense pathways remains poorly defined. Recently, several studies have reported that growth at elevated CO2 is sufficient to induce defenses such as the salicylic acid pathway, thereby increasing plant resistance to pathogens. These reports contrast with evidence that defense pathways can be promoted by photorespiration, which is inhibited at high CO2. Here, we review signaling, metabolic, and redox processes modulated by CO2 levels and discuss issues to be resolved in elucidating the relationships between primary metabolism, inducible defense, and biotic stress resistance.
Pathogenesis-related (PR) responses are closely integrated with primary metabolism and influenced by simple compounds involved in plant nutrition, such as sugars, organic acids, and amino acids.
Photorespiratory metabolism linked to enhanced production of reactive oxygen species (ROS) in peroxisomes can induce typical PR responses.
Growing plants at increased CO2 levels, which slows photorespiratory rates, can also induce defense metabolism and PR genes, effects that are accompanied by upregulation of ROS signaling.
Genes involved in CO2 sensing and signaling in stomatal regulation are beginning to be elucidated but components that link CO2 availability to biotic stress responses remain to be identified.
Emerging evidence suggests that metabolite and ROS signaling are likely to be important in linking CO2 availability to the activation of defense metabolism.
The full article appears on the Trends in Plant Science website at http://www.cell.com/trends/plant-science/fulltext/S1360-1385(17)30157-7?_returnURL=http%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS1360138517301577%3Fshowall%3Dtrue