Figure 10

Expression profiles of genes encoding proteins producing or detoxifying reactive oxygen species (ROS) in chickpea roots and nodules. A) In the very intricate ROS pathway in legume nodules, superoxide radicals (O₂^-) are generated by elevated mitochondrial respiration rates. In turn, leghemoglobin (LB²⁺), the enzyme keeping the nodules free of molecular oxygen (O₂), can spontaneously be converted to ferric LB (LB³⁺), generating new O₂^-. These radicals can induce further conversions of LB²⁺ to LB³⁺. The generated superoxide radical can be directly dismutated by SOD to H₂O₂, which is immediately decomposed, as depicted in (B). On the other hand, H₂O₂ can generate hydroxyl radicals (OH^-) in the presence of abundant free Fe⁺ ions, which are sequestered by metallothionein-like proteins. B) Hydrogen peroxide can be scavenged via the glutathione/ascorbate cycles or the action of catalases (CAT) NC: UniTag expression profiles indicating prevalence in nodules (with various intensities of blue):Organ-specific expression NS and RS: UniTag expression profiles of roots and nodules, and up- and down-regulation under salt stress (with various intensities of red and green, respectively): Stress-specific expression