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Autophagy contributes to regulation of the hypoxia response during submergence in Arabidopsis thaliana.

Chen L, Liao B, Qi H, Xie LJ, Huang L, Tan WJ, Zhai N, Yuan LB, Zhou Y, Yu LJ, Chen QF, Shu W, Xiao S - Autophagy (2015)

Bottom Line: Both submergence and ethanol treatments induce the accumulation of reactive oxygen species (ROS) in the rosettes of atg mutants more than in the wild type.Moreover, the production of ROS by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidases is necessary for plant tolerance to submergence and ethanol, submergence-induced expression of ADH1 and PDC1, and activation of autophagy.The submergence- and ethanol-sensitive phenotypes in the atg mutants depend on a complete salicylic acid (SA) signaling pathway.

View Article: PubMed Central - PubMed

Affiliation: a State Key Laboratory of Biocontrol; Guangdong Provincial Key Laboratory of Plant Resources; Collaborative Innovation Center of Genetics and Development; School of Life Sciences; Sun Yat-sen University ; Guangzhou , China.

ABSTRACT
Autophagy involves massive degradation of intracellular components and functions as a conserved system that helps cells to adapt to adverse conditions. In mammals, hypoxia rapidly stimulates autophagy as a cell survival response. Here, we examine the function of autophagy in the regulation of the plant response to submergence, an abiotic stress that leads to hypoxia and anaerobic respiration in plant cells. In Arabidopsis thaliana, submergence induces the transcription of autophagy-related (ATG) genes and the formation of autophagosomes. Consistent with this, the autophagy-defective (atg) mutants are hypersensitive to submergence stress and treatment with ethanol, the end product of anaerobic respiration. Upon submergence, the atg mutants have increased levels of transcripts of anaerobic respiration genes (alcohol dehydrogenase 1, ADH1 and pyruvate decarboxylase 1, PDC1), but reduced levels of transcripts of other hypoxia- and ethylene-responsive genes. Both submergence and ethanol treatments induce the accumulation of reactive oxygen species (ROS) in the rosettes of atg mutants more than in the wild type. Moreover, the production of ROS by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidases is necessary for plant tolerance to submergence and ethanol, submergence-induced expression of ADH1 and PDC1, and activation of autophagy. The submergence- and ethanol-sensitive phenotypes in the atg mutants depend on a complete salicylic acid (SA) signaling pathway. Together, our findings demonstrate that submergence-induced autophagy functions in the hypoxia response in Arabidopsis by modulating SA-mediated cellular homeostasis.

No MeSH data available.


Related in: MedlinePlus

Role of ROS in the autophagy-mediated plant response to submergence and ethanol stresses. (A) Relative expression levels of genes encoding enzymes involved in production or reduction of ROS after light submergence (LS) treatment. Four-wk-old wild type (WT) and atg mutants (atg5-1 and atg7-3) upon LS treatment at 0, 3, 6, and 24 h were collected for total RNA extraction. The relative mRNA abundance was normalized to that of ACT2. The experiments have been repeated 3 times (biological replicates) with similar results and the representative data from one replicate are shown. Data are average values ± SD (n = 3) of 3 technical replicates. Asterisks indicate significant differences from WT (*, P < 0.05; **, P < 0.01 by the Student t test). (B, C) DAB staining showing the accumulation of ROS in the leaves of 4-wk-old atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) under normal growth conditions (Light), 3-d treatment with LS (B) and 100 mM ethanol (C). In contrast to weak signals in the WT leaves, strong ROS accumulation was detected in the atg mutants after LS and ethanol treatments. Scale bar: 500 μm.
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f0005: Role of ROS in the autophagy-mediated plant response to submergence and ethanol stresses. (A) Relative expression levels of genes encoding enzymes involved in production or reduction of ROS after light submergence (LS) treatment. Four-wk-old wild type (WT) and atg mutants (atg5-1 and atg7-3) upon LS treatment at 0, 3, 6, and 24 h were collected for total RNA extraction. The relative mRNA abundance was normalized to that of ACT2. The experiments have been repeated 3 times (biological replicates) with similar results and the representative data from one replicate are shown. Data are average values ± SD (n = 3) of 3 technical replicates. Asterisks indicate significant differences from WT (*, P < 0.05; **, P < 0.01 by the Student t test). (B, C) DAB staining showing the accumulation of ROS in the leaves of 4-wk-old atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) under normal growth conditions (Light), 3-d treatment with LS (B) and 100 mM ethanol (C). In contrast to weak signals in the WT leaves, strong ROS accumulation was detected in the atg mutants after LS and ethanol treatments. Scale bar: 500 μm.

Mentions: Given that anoxia induces NADPH oxidase-dependent accumulation of H2O2 in Arabidopsis,23 we hypothesized that autophagy plays a role in controlling ROS levels under submergence. To examine this, we used qRT-PCR to measure the transcript levels of genes encoding RBOHD (respiratory burst oxidase homolog D) and RBOHF, 2 major ROS-generating enzymes.42 As shown in Figure 5A, the expression of RBOHD and RBOHF was significantly upregulated in the atg mutants in comparison to the wild type at 0, 3, and 24 h of submergence (LS). However, the transcript levels of CAT1 (catalase 1), APX1 (ascorbate peroxidase 1), GPX1 (glutathione peroxidase 1), and GR1 (glutathione-disulfide reductase 1), which encode enzymes that detoxify H2O2 in plants,43 were downregulated in the atg mutants at 0, 3, 6, and 24 h of submergence in comparison to the wild type, except the transcript levels of GPX1 and APX1 were similar at 0 and 6 h, respectively, to those of the wild type (Fig. 5A).Figure 5.


Autophagy contributes to regulation of the hypoxia response during submergence in Arabidopsis thaliana.

Chen L, Liao B, Qi H, Xie LJ, Huang L, Tan WJ, Zhai N, Yuan LB, Zhou Y, Yu LJ, Chen QF, Shu W, Xiao S - Autophagy (2015)

Role of ROS in the autophagy-mediated plant response to submergence and ethanol stresses. (A) Relative expression levels of genes encoding enzymes involved in production or reduction of ROS after light submergence (LS) treatment. Four-wk-old wild type (WT) and atg mutants (atg5-1 and atg7-3) upon LS treatment at 0, 3, 6, and 24 h were collected for total RNA extraction. The relative mRNA abundance was normalized to that of ACT2. The experiments have been repeated 3 times (biological replicates) with similar results and the representative data from one replicate are shown. Data are average values ± SD (n = 3) of 3 technical replicates. Asterisks indicate significant differences from WT (*, P < 0.05; **, P < 0.01 by the Student t test). (B, C) DAB staining showing the accumulation of ROS in the leaves of 4-wk-old atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) under normal growth conditions (Light), 3-d treatment with LS (B) and 100 mM ethanol (C). In contrast to weak signals in the WT leaves, strong ROS accumulation was detected in the atg mutants after LS and ethanol treatments. Scale bar: 500 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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f0005: Role of ROS in the autophagy-mediated plant response to submergence and ethanol stresses. (A) Relative expression levels of genes encoding enzymes involved in production or reduction of ROS after light submergence (LS) treatment. Four-wk-old wild type (WT) and atg mutants (atg5-1 and atg7-3) upon LS treatment at 0, 3, 6, and 24 h were collected for total RNA extraction. The relative mRNA abundance was normalized to that of ACT2. The experiments have been repeated 3 times (biological replicates) with similar results and the representative data from one replicate are shown. Data are average values ± SD (n = 3) of 3 technical replicates. Asterisks indicate significant differences from WT (*, P < 0.05; **, P < 0.01 by the Student t test). (B, C) DAB staining showing the accumulation of ROS in the leaves of 4-wk-old atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) under normal growth conditions (Light), 3-d treatment with LS (B) and 100 mM ethanol (C). In contrast to weak signals in the WT leaves, strong ROS accumulation was detected in the atg mutants after LS and ethanol treatments. Scale bar: 500 μm.
Mentions: Given that anoxia induces NADPH oxidase-dependent accumulation of H2O2 in Arabidopsis,23 we hypothesized that autophagy plays a role in controlling ROS levels under submergence. To examine this, we used qRT-PCR to measure the transcript levels of genes encoding RBOHD (respiratory burst oxidase homolog D) and RBOHF, 2 major ROS-generating enzymes.42 As shown in Figure 5A, the expression of RBOHD and RBOHF was significantly upregulated in the atg mutants in comparison to the wild type at 0, 3, and 24 h of submergence (LS). However, the transcript levels of CAT1 (catalase 1), APX1 (ascorbate peroxidase 1), GPX1 (glutathione peroxidase 1), and GR1 (glutathione-disulfide reductase 1), which encode enzymes that detoxify H2O2 in plants,43 were downregulated in the atg mutants at 0, 3, 6, and 24 h of submergence in comparison to the wild type, except the transcript levels of GPX1 and APX1 were similar at 0 and 6 h, respectively, to those of the wild type (Fig. 5A).Figure 5.

Bottom Line: Both submergence and ethanol treatments induce the accumulation of reactive oxygen species (ROS) in the rosettes of atg mutants more than in the wild type.Moreover, the production of ROS by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidases is necessary for plant tolerance to submergence and ethanol, submergence-induced expression of ADH1 and PDC1, and activation of autophagy.The submergence- and ethanol-sensitive phenotypes in the atg mutants depend on a complete salicylic acid (SA) signaling pathway.

View Article: PubMed Central - PubMed

Affiliation: a State Key Laboratory of Biocontrol; Guangdong Provincial Key Laboratory of Plant Resources; Collaborative Innovation Center of Genetics and Development; School of Life Sciences; Sun Yat-sen University ; Guangzhou , China.

ABSTRACT
Autophagy involves massive degradation of intracellular components and functions as a conserved system that helps cells to adapt to adverse conditions. In mammals, hypoxia rapidly stimulates autophagy as a cell survival response. Here, we examine the function of autophagy in the regulation of the plant response to submergence, an abiotic stress that leads to hypoxia and anaerobic respiration in plant cells. In Arabidopsis thaliana, submergence induces the transcription of autophagy-related (ATG) genes and the formation of autophagosomes. Consistent with this, the autophagy-defective (atg) mutants are hypersensitive to submergence stress and treatment with ethanol, the end product of anaerobic respiration. Upon submergence, the atg mutants have increased levels of transcripts of anaerobic respiration genes (alcohol dehydrogenase 1, ADH1 and pyruvate decarboxylase 1, PDC1), but reduced levels of transcripts of other hypoxia- and ethylene-responsive genes. Both submergence and ethanol treatments induce the accumulation of reactive oxygen species (ROS) in the rosettes of atg mutants more than in the wild type. Moreover, the production of ROS by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidases is necessary for plant tolerance to submergence and ethanol, submergence-induced expression of ADH1 and PDC1, and activation of autophagy. The submergence- and ethanol-sensitive phenotypes in the atg mutants depend on a complete salicylic acid (SA) signaling pathway. Together, our findings demonstrate that submergence-induced autophagy functions in the hypoxia response in Arabidopsis by modulating SA-mediated cellular homeostasis.

No MeSH data available.


Related in: MedlinePlus