In metazoans, from humans to Caenorhabditis elegans, the central regulators of PCD are well characterized and conserved involving pro- and anti-apoptotic protein such as APAF-1/CED-4 and BCL-2/CED-9, and executing protein family Y-27632 ROCK inhibitor caspasas/CED3. Interestingly, although these regulators are absent in the genomes of plants and yeast, the effects of animal pro and antiapoptotic proteins has been studied in transgenic plants. According to the localization of these heterologous proteins in plant cells, it is proposed that cell death suppressors contribute to maintain the organelles homeostasis preventing the generation/ release of death signals, similar to what occurs in animals. However, there are limited data regarding the mechanisms through which the animal cell death suppressors modulate the plant physiology. Remarkably, the expression of PCD suppressors in plants result in agronomical beneficial features such as improved tolerance to a variety of biotic and abiotic stresses. Increased the biological nitrogen fixation in legumes is a main objective for the agriculture, and different strategies had been explored towards this objective. During the natural or stress induced senescence, which involve cell death processes, the biological nitrogen fixation metabolism is impaired, affecting both quality and quantity of legume yields. Therefore, the development of strategies to increase the tolerance to a variety of stresses is highly relevant. To the best of our knowledge, the effect of animal PCD suppressor has not been tested in legumes. In contrast, under 150 mM NaCl, the intracellular ROS production decreased from the beginning of treatment independently of the presence of the symbiont. The aim of the present work was to evaluate if the expression of Ced-9 from Caenorhabditis elegans could improve the stress tolerance of legume-rizobia symbiotic interaction and the biological nitrogen fixation process. Transgenic soybean-hairy roots expressing Ced-9, obtained with Agrobacterium rhizogenes, were subjected to the above described cell death-inducing conditions, in order to evaluate root cell viability, redox and ionic parameters associated and nodule development. Soybean-rhizobia symbiotic interaction is severely affected by salt stress, showing a reduction on number and weight of nodules in plants salinized with 26 mM NaCl. Our group had studied the effects of salt stress conditions on early events of Glycine max L.-B. japonicum symbiotic interaction, where undescribed root hairs death-inducing conditions were identified: sub lethal salt stress treatments combined with B. japonicum and severe salt stress . During the early events of symbiotic interaction, a fast and transient increase of intracellular ROS generation take place in root hairs, whereas a sustained ROS production was reported when the symbiotic interaction occurred under 50 mM NaCl. A similar root hair ROS kinetic was observed in response to pathogenic elicitors.