Abstract
Polyamines (PAs) belong to plant growth regulators and in complex with classical phytohormones take part in regulation of seed dormancy and germination. Although the impact of reactive oxygen (ROS) and nitrogen (RNS) species on seed germination is well described, the cross talk of PAs with ROS/RNS has never been analyzed. Due to the close connection of PAs and ethylene biosynthetic pathways to arginine (Arg)-dependent NO biosynthesis we investigated production of nitric oxide (NO), peroxynitrite (ONOO−) and the level of O2•− or H2O2 in apple embryos, germination of which was PA regulated. PAs: putrescine (Put) and spermidine (Spd) in contrast to spermine (Spm) stimulated germination of apple embryos. Among amino acids, stimulation of germination was observed in Arg and ornithine (Orn) only. Dormancy removal of embryos by PAs was associated with increased accumulation of H2O2 and O2•− in embryonic axes. At the same stage of completion of sensu stricto germination the stimulatory effect of PAs (Put and Spd) and amino acids, mainly Arg and Orn, was accompanied by enhanced NO and ONOO− production in embryonic axis. The beneficial effect of PAs (Put and Spd) and their precursors on germination of apple embryos was removed by NO scavenging, suggesting a crucial role of NO in termination of embryo germination and radicle growth. Moreover, activity of polyamine oxidase in embryo axes was greatly enhanced by embryo fumigation with NO. Our data demonstrate the interplay of RNS/ROS with PAs and point to NO action as an integrator of endogenous signals activating germination.
Highlights
Polyamines (PAs) are low molecular weight aliphatic cations
Embryos germinated in PAs or amino acids at the concentration that exhibited the best effect on germination [Put (0.1 mM), Spd (0.2 mM) and Arg (0.1 mM), Orn (0.2 mM) and Met (0.1 mM)] or significantly inhibited germination—[Spm (0.3 mM)], and control embryos after 2 days of culture and at the physiological stage of termination of germination sensu stricto were used for the experiment
In the present study the impact of PAs and their precursors on the apple embryo germination was investigated in relation to the nitric oxide (NO) beneficial effect on dormancy alleviation
Summary
Polyamines (PAs) are low molecular weight aliphatic cations. They are widespread in diverse organisms including higher plants and act as modulators of many developmental and physiological processes reactions to stresses (Baron and Stasolla 2008; Kusano and others 2008; Takahashi and Kakehi 2010). Regulation of seed dormancy and germination depends on the activity of several endogenous factors including classical phytohormones such as gibberellins (GAs) (Kucera and others 2005), abscisic acid (ABA) (Kermode 2005), or ethylene (Matilla and Matilla-Vazquez 2008; Bogatek and Gniazdowska 2012); plant growth regulators, for example, PAs (Matilla 1996); and signaling molecules such as reactive oxygen (ROS) or reactive nitrogen (RNS) species (Bailly and others 2008; Sirovaand others 2011). The aim of our work was to investigate the impact of three PAs (Put, Spd, and Spm) and their precursors (amino acids: Arg, Orn, and Met) on dormancy alleviation of apple embryos in relation to the regulatory role of ROS (H2O2 and O2-) and RNS (NO and ONOO-) during sensu stricto germination, by measurement of ROS and RNS level/production. To our knowledge the presented data are absolutely only one of their kind, as no more than Tun and others (2006) demonstrated a direct impact of PAs on NO generation, whereas Yamasaki and Cohen (2006) and recently Wimalasekera and others (2011) presented a hypothesis linking PAs and NO metabolism
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