Cobalt Alleviates GA-Induced Programmed Cell Death in Wheat Aleurone Layers via the Regulation of H2O2 Production and Heme Oxygenase-1 Expression

Abstract

Heme oxygenase-1 (HO-1) and hydrogen peroxide (H2O2) are key signaling molecules that are produced in response to various environmental stimuli. Here, we demonstrate that cobalt is able to delay gibberellic acid (GA)-induced programmed cell death (PCD) in wheat aleurone layers. A similar response was observed when samples were pretreated with carbon monoxide (CO) or bilirubin (BR), two end-products of HO catalysis. We further observed that increased HO-1 expression played a role in the cobalt-induced alleviation of PCD. The application of HO-1-specific inhibitor, zinc protoporphyrin-IX (ZnPPIX), substantially prevented the increases of HO-1 activity and the alleviation of PCD triggered by cobalt. The stimulation of HO-1 expression, and alleviation of PCD might be caused by the initial H2O2 production induced by cobalt. qRT-PCR and enzymatic assays revealed that cobalt-induced gene expression and the corresponding activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), three enzymes that metabolize reactive oxygen species, were consistent with the H2O2 accumulation during GA treatment. These cobalt responses were differentially blocked by co-treatment with ZnPPIX. We therefore suggest that HO-1 functions in the cobalt-triggered alleviation of PCD in wheat aleurone layers, which is also dependent on the enhancement of the activities of antioxidant enzymes.

Heme Oxygenase-1 Delays Gibberellin-Induced Programmed Cell Death of Rice Aleurone Layers Subjected to Drought Stress by Interacting with Nitric Oxide

“…In addition, haematin blocked the decrease of GA-induced ascorbate peroxidase (APX) and CAT activities, and then resulted in the decrease of H 2 O 2 level, and these effects were reversed by HO-1 inhibitor ZnPPIX ( Wu et al, 2011 ). The up-regulation of HO-1 would contribute to the capability of HO, act as a potent antioxidant enzyme, eliminating ROS and protecting cells from oxidative stress in wheat aleurone layers ( Wu et al, 2011 , 2014 ), which has previously been confirmed in plants ( Noriega et al, 2004 ; Han et al, 2008 ). The present study showed that the up-regulation of HO contributed to the delay in PCD in rice aleurone layers induced by GA under drought stress, the similar results were obtained by Wu et al (2011 , 2014 ).…”

“…The up-regulation of HO-1 would contribute to the capability of HO, act as a potent antioxidant enzyme, eliminating ROS and protecting cells from oxidative stress in wheat aleurone layers ( Wu et al, 2011 , 2014 ), which has previously been confirmed in plants ( Noriega et al, 2004 ; Han et al, 2008 ). The present study showed that the up-regulation of HO contributed to the delay in PCD in rice aleurone layers induced by GA under drought stress, the similar results were obtained by Wu et al (2011 , 2014 ). Above mentioned results revealed that HO-1 function in the PCD of cereal aleurone layers is dependent on enhancing the activities of antioxidant enzymes.…”

“…The role of HO-1 in regulating PCD by GA, NO, and H 2 O 2 has been elucidated in wheat ( Wu et al, 2011 , 2014 ). However, the role of HO-1 in regulating PCD, particularly the morphological changes involving vacuoles has not been investigated in rice aleurone layers.…”

Reactive Oxygen Species and Gibberellin Acid Mutual Induction to Regulate Tobacco Seed Germination

“…Nevertheless, H 2 O 2 releases embryo dormancy in barley by activating GA signaling and synthesis rather than the repression of ABA signaling ( Bahin et al, 2011 ). GA biosynthesizes in embryo during the germination and induces H 2 O 2 production in wheat aleurone cells; H 2 O 2 subsequently acts as a signal molecule to antagonize ABA signaling ( Wu et al, 2014 ). Additional evidence has suggested that GA induces the germination of dormant caryopses by regulating the level of ABA and the ROS-antioxidant status ( Cembrowska-Lech et al, 2015 ).…”

Exogenous Hydrogen Peroxide Contributes to Heme Oxygenase-1 Delaying Programmed Cell Death in Isolated Aleurone Layers of Rice Subjected to Drought Stress in a cGMP-Dependent Manner

“…As expected, the beneficial effect of exogenous H 2 O 2 in rice aleurone layers is supported by some studies that showed, for example, that exogenous application of H 2 O 2 enhanced the activities of the antioxidant enzymes SOD, CAT, and APX, and also reduced the content of MDA in wheat and maize subjected to salt stress ( Li et al, 2011 ; Gondim et al, 2012 ), and that endogenous H 2 O 2 levels were not enhanced by the addition of a low concentration H 2 O 2 in seedlings for 24 or 48 h prior to drought stress or salt stress ( Fedina et al, 2009 ; Hossain and Fujita, 2013 ). Subsequent experiments revealed that the HO-1 inducer hematin can mimic the effects of the antioxidants AsA and DMTU on down-regulating endogenous H 2 O 2 levels ( Figure 2 ), indicating that HO-1 may act as a potent antioxidative enzyme in the protection of cells from oxidative stress ( Wu et al, 2011 , 2014 ). Our experiments also revealed that DPI, an NADPH synthase inhibitor, significantly inhibited H 2 O 2 levels ( Figure 2 ).…”