Inactivation of Carbonyl-Detoxifying Enzymes by H2O2 Is a Trigger to Increase Carbonyl Load for Initiating Programmed Cell Death in Plants.

Md Sanaullah Biswas,Ryota Terada,Jun'Ichi Mano

doi:10.3390/antiox9020141

Md Sanaullah Biswas, Ryota Terada + Show 1 more

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https://doi.org/10.3390/antiox9020141

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Abstract

H2O2-induced programmed cell death (PCD) of tobacco Bright Yellow-2 (BY-2) cells is mediated by reactive carbonyl species (RCS), degradation products of lipid peroxides, which activate caspase-3-like protease (C3LP). Here, we investigated the mechanism of RCS accumulation in the H2O2-induced PCD of BY-2 cells. The following biochemical changes were observed in 10-min response to a lethal dose (1.0 mM) of H2O2, but they did not occur in a sublethal dose (0.5 mM) of H2O2. (1) The C3LP activity was increased twofold. (2) The intracellular levels of RCS, i.e., 4-hydroxy-(E)-hexenal and 4-hydroxy-(E)-nonenal (HNE), were increased 1.2–1.5-fold. (3) The activity of a reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent carbonyl reductase, scavenging HNE, and n-hexanal was decreased. Specifically, these are the earliest events leading to PCD. The proteasome inhibitor MG132 suppressed the H2O2-induced PCD, indicating that the C3LP activity of the β1 subunit of the 20S proteasome was responsible for PCD. The addition of H2O2 to cell-free protein extract inactivated the carbonyl reductase. Taken together, these results suggest a PCD-triggering mechanism in which H2O2 first inactivates a carbonyl reductase(s), allowing RCS levels to rise, and eventually leads to the activation of the C3LP activity of 20S proteasome. The carbonyl reductase thus acts as an ROS sensor for triggering PCD.

Highlights

Reactive oxygen species (ROS), such as superoxide radical and hydrogen peroxide (H2 O2 ), are metabolic outcomes of various cellular processes in plants
We reported that tobacco Bright Yellow-2 (BY-2) cells exposed to H2 O2 generated acrolein and HNE, and a chemical carbonyl scavenger prevented the initiation of programmed cell death (PCD), without affecting the increase in the intracellular ROS level [12]
In our previous study [20], we found that H2 O2 addition to BY-2 cells activated both caspase-3-like protease (C3LP) and caspase-1-like protease (C1LP) before PCD

Summary

Introduction

Reactive oxygen species (ROS), such as superoxide radical and hydrogen peroxide (H2 O2 ), are metabolic outcomes of various cellular processes in plants. Versatile biological actions of ROS, collectively termed as oxidative signals, largely depends on the ROS concentration [1]. Recent evidence shows that ROS are involved in diverse signaling functions in plants, from cell cycle regulation to whole plant senescence [2]. The transition from cellular proliferation to cell elongation, which is necessary for plant growth in the early stages of cell differentiation, is regulated by ROS signals [3]. The levels of superoxide radical and H2 O2 are high in the elongation and meristematic zone of Arabidopsis root [4]. ROS play an important role in seed germination; superoxide and H2 O2 are increased in the radicle

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