NO, hydrogen sulfide does not come first during tomato response to high salinity

High salinity greatly impacts agriculture, particularly in tomato (Solanum lycopersicum), a crop that is a model to study this abiotic stress. This work investigated whether hydrogen sulfide (H₂S) acts upstream or downstream of nitric oxide (NO) in the signaling cascade during tomato response to salt stress. An NO-donor incremented H₂S levels by 12-18.9% while an H₂S-donor yielded 10% more NO in roots. The NO accumulated in roots one-hour after NaCl treatment while H₂S accumulation started two-hour later. The NO stimulated H₂S accumulation in roots/leaves, but not the opposite (i.e H₂S was unable to stimulate NO accumulation) two-hour post NaCl treatment. Also, NO accumulation was accompanied by an increment of transcript levels of genes that encode for H₂S-synthesizing enzymes. Our results indicate that H₂S acts downstream of NO in the mitigation of oxidative stress, which helps tomato plants to tolerate high salinity.