Abstract
Sulfur dioxide (SO2), a gaseous signaling molecule in animal cells, has recently been found to play a physiological role in plants. Here we studied the role of SO2 in gibberellic acid (GA3)-induced programmed cell death (PCD) in barley (Hordeum vulgare L.) aleurone layers. The application of the SO2 donor (NaHSO3/Na2SO3, 1:3 M/M) effectively alleviated PCD in barley aleurone layers in a dose-dependent manner with an optimal concentration of 50 μM. Further investigations showed that SO2 reduced the accumulation of hydrogen peroxide (H2O2), superoxide anion (⋅O2−) and malondialdehyde (MDA) in aleurone layers. Moreover, the activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and guaiacol peroxidase (POD) were enhanced by SO2 donor treatment. Meanwhile, lipoxygenase (LOX) activity was attenuated by SO2 donor treatment. Furthermore, an induction of endogenous H2S and NO were also observed in SO2-treated aleurone layers, suggesting interactions of SO2 with other well-known signaling molecules. Taken together, we show that SO2 negatively regulated PCD by acting as an antioxidant to scavenge excessive reactive oxygen species (ROS) generated during PCD.
Highlights
Programmed cell death (PCD), a form of cell death initiated and regulated by genes, is a common physiological process during plant development [1]
PCD in cereal aleurone cells occurs after germination, a process that is tightly regulated by gibberellic acid (GA3) and abscisic acid (ABA) [2]
To study whether SO2 is involved in hormonally regulated PCD in aleurone layers, SO2 concentrations ranging from 0 to 500 μM was applied to barley aleurone layers subjected to 20 μM GA3, and the viability of aleurone cells was monitored at 24 and 48 h (Fig 1)
Summary
Programmed cell death (PCD), a form of cell death initiated and regulated by genes, is a common physiological process during plant development [1]. The cereal aleurone layer is a specialized tissue whose function is to synthesize and secrete hydrolytic enzymes that break down reserves in the starchy endosperm. The process of aleurone cell death is a form of PCD. PCD in cereal aleurone cells occurs after germination, a process that is tightly regulated by gibberellic acid (GA3) and abscisic acid (ABA) [2]. Reactive oxygen species (ROS) such as superoxide anion (ÁO2−), hydrogen peroxide (H2O2) and hydroxyl radicals are key players in the PCD process in both plant and animal cells [3]. ROS, especially hydrogen peroxide, are key players in the hormone-induced PCD [4].
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