Oxygen is partially reduced into reactive oxygen species (ROS) during aerobic metabolism. In plant cells ROS are produced in the various cell compartments. This work is focused on the g-ECS gene that encodes for g-ECS. The major findings of this work are the tomato g-ECS protein encodes for a 523-amino acid and is encoded by a single gene. The identification of IL 8-3 as harboring the Lpa g-ECS ortholog, assigned this gene to chromosome 8. g-ECS was found to be expressed in various organs of the two tomato species. Based on the finding that the transcription level of ?-ECS was upregulated under salinity and cadmium stresses, only and similarly in Lpa and IL 8-3, it was concluded that the lack of this up-regulation in Lem under stress results from a mutation in its cis-regulatory element(s) and not in gene(s) encoding trans-regulatory factor(s).