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 (HS) acts upstream or downstream of nitric oxide (NO) in the signaling cascade during tomato response to salt stress. An NO-donor incremented HS levels by 12-18.9% while an HS-donor yielded 10% more NO in roots. The NO accumulated in roots one-hour after NaCl treatment while HS accumulation started two-hour later. The NO stimulated HS accumulation in roots/leaves, but not the opposite (i.e HS 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 HS-synthesizing enzymes. Our results indicate that HS acts downstream of NO in the mitigation of oxidative stress, which helps tomato plants to tolerate high salinity.