Abstract
The mechanisms by which the expression of animal cell death suppressors in economically important plants conferred enhanced stress tolerance are not fully understood. In the present work, the effect of expression of animal antiapoptotic gene Ced-9 in soybean hairy roots was evaluated under root hairs and hairy roots death-inducing stress conditions given by i) Bradyrhizobium japonicum inoculation in presence of 50 mM NaCl, and ii) severe salt stress (150 mM NaCl), for 30 min and 3 h, respectively. We have determined that root hairs death induced by inoculation in presence of 50 mM NaCl showed characteristics of ordered process, with increased ROS generation, MDA and ATP levels, whereas the cell death induced by 150 mM NaCl treatment showed non-ordered or necrotic-like characteristics. The expression of Ced-9 inhibited or at least delayed root hairs death under these treatments. Hairy roots expressing Ced-9 had better homeostasis maintenance, preventing potassium release; increasing the ATP levels and controlling the oxidative damage avoiding the increase of reactive oxygen species production. Even when our results demonstrate a positive effect of animal cell death suppressors in plant cell ionic and redox homeostasis under cell death-inducing conditions, its expression, contrary to expectations, drastically inhibited nodule formation even under control conditions.
Highlights
Programmed cell death (PCD) is a genetically regulated process of cellular suicide and is well known to play a fundamental role in a wide variety of developmental and physiological functions in animals, plants, and fungi [1,2,3]
Two root hairs deathinducing conditions were identified: sub lethal salt stress treatments combined with B. japonicum inoculation and severe salt stress (150 mM NaCl)
The Malondialdehyde content (MDA) level increased in inoculated and inoculated 50 mM NaCl treatments, whereas non significant differences were observed in salt stress alone (50 mM NaCl and 150 mM NaCl) respect to control (Fig. 2A)
Summary
Programmed cell death (PCD) is a genetically regulated process of cellular suicide and is well known to play a fundamental role in a wide variety of developmental and physiological functions in animals, plants, and fungi [1,2,3]. 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 caspasas/CED3 [9,10]. 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 [11,12,13,14,15,16,17,18]. 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 [11,13]
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