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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

Autophagy-defective mutants show enhanced sensitivity to submergence. (A) Images of the wild type (WT) and atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) before treatment (Day 0) and at 6 d after light submergence (LS) treatment (Day 6), followed by a 6-d recovery (Recovery). (B) Dry weights and (C) survival rates of WT and atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) after 6-d LS treatment following recovery. Data of dry weights and survival rates are average values ± SD (n = 3) calculated from 3 independent experiments. For each experiment, 10 plants were used for each genotype. Asterisks indicate significant differences from WT (**, P < 0.01 by the Student t test). (D) Immunoblot analyses of ATG8 protein in WT and atg mutants (atg5-1 and atg7-3) upon LS treatment. Four-wk-old plants were not treated (0 h) and LS-treated for 24, 48, and 72 h, and leaves were collected. The anti-ATG8a antibodies were used for immunoblotting. (E) Detection of free GFP generated from transgenic lines expressing GFP-ATG8e in WT, atg5-1 backgrounds before and after LS treatment. Four-wk-old plant samples were collected at 0, 12, 24, and 48 h after treatment. The anti-GFP antibodies were used for protein blotting analysis. The GFP-ATG8e fusion and free GFP form were indicated on the right. Coomassie blue–stained total proteins are shown on the right (D) or below the blots (E) to indicate the amount of protein loaded per lane.
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f0002: Autophagy-defective mutants show enhanced sensitivity to submergence. (A) Images of the wild type (WT) and atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) before treatment (Day 0) and at 6 d after light submergence (LS) treatment (Day 6), followed by a 6-d recovery (Recovery). (B) Dry weights and (C) survival rates of WT and atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) after 6-d LS treatment following recovery. Data of dry weights and survival rates are average values ± SD (n = 3) calculated from 3 independent experiments. For each experiment, 10 plants were used for each genotype. Asterisks indicate significant differences from WT (**, P < 0.01 by the Student t test). (D) Immunoblot analyses of ATG8 protein in WT and atg mutants (atg5-1 and atg7-3) upon LS treatment. Four-wk-old plants were not treated (0 h) and LS-treated for 24, 48, and 72 h, and leaves were collected. The anti-ATG8a antibodies were used for immunoblotting. (E) Detection of free GFP generated from transgenic lines expressing GFP-ATG8e in WT, atg5-1 backgrounds before and after LS treatment. Four-wk-old plant samples were collected at 0, 12, 24, and 48 h after treatment. The anti-GFP antibodies were used for protein blotting analysis. The GFP-ATG8e fusion and free GFP form were indicated on the right. Coomassie blue–stained total proteins are shown on the right (D) or below the blots (E) to indicate the amount of protein loaded per lane.

Mentions: To assess the cellular function of autophagy in the submergence response, we characterized 4 autophagy-deficient mutants, atg2-1, atg5-1, atg7-3, and atg10-1, from the SALK and SAIL T-DNA insertion pools (Figs. S2 and S3) and tested their responses to submergence. The 4-wk-old atg mutants showed few phenotypic differences to the wild type under normal growth conditions. When the plants were LS-treated for 6 d or DS-treated for 2 d, all atg mutants displayed enhanced sensitivity to both treatments (Fig. 2A; Fig. S4A), while 2-d dark treatment alone did not cause obvious phenotypic differences between the wild type and atg mutants (Fig. S4A). Following recovery for 6 d, the atg mutants showed significant hypersensitivity to submergence under LS and DS conditions, in comparison to the wild-type control, as shown by calculating the dry weights and survival rates of the plants (Fig. 2A, B and C; Fig. S4A and S4B). Moreover, when the plants were treated with LS for various times, we clearly observed damage in the atg mutant leaves at 3 d after treatment in comparison to the wild type, which showed little damage (Fig. S5).Figure 2.


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)

Autophagy-defective mutants show enhanced sensitivity to submergence. (A) Images of the wild type (WT) and atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) before treatment (Day 0) and at 6 d after light submergence (LS) treatment (Day 6), followed by a 6-d recovery (Recovery). (B) Dry weights and (C) survival rates of WT and atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) after 6-d LS treatment following recovery. Data of dry weights and survival rates are average values ± SD (n = 3) calculated from 3 independent experiments. For each experiment, 10 plants were used for each genotype. Asterisks indicate significant differences from WT (**, P < 0.01 by the Student t test). (D) Immunoblot analyses of ATG8 protein in WT and atg mutants (atg5-1 and atg7-3) upon LS treatment. Four-wk-old plants were not treated (0 h) and LS-treated for 24, 48, and 72 h, and leaves were collected. The anti-ATG8a antibodies were used for immunoblotting. (E) Detection of free GFP generated from transgenic lines expressing GFP-ATG8e in WT, atg5-1 backgrounds before and after LS treatment. Four-wk-old plant samples were collected at 0, 12, 24, and 48 h after treatment. The anti-GFP antibodies were used for protein blotting analysis. The GFP-ATG8e fusion and free GFP form were indicated on the right. Coomassie blue–stained total proteins are shown on the right (D) or below the blots (E) to indicate the amount of protein loaded per lane.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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f0002: Autophagy-defective mutants show enhanced sensitivity to submergence. (A) Images of the wild type (WT) and atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) before treatment (Day 0) and at 6 d after light submergence (LS) treatment (Day 6), followed by a 6-d recovery (Recovery). (B) Dry weights and (C) survival rates of WT and atg mutants (atg2-1, atg5-1, atg7-3, and atg10-1) after 6-d LS treatment following recovery. Data of dry weights and survival rates are average values ± SD (n = 3) calculated from 3 independent experiments. For each experiment, 10 plants were used for each genotype. Asterisks indicate significant differences from WT (**, P < 0.01 by the Student t test). (D) Immunoblot analyses of ATG8 protein in WT and atg mutants (atg5-1 and atg7-3) upon LS treatment. Four-wk-old plants were not treated (0 h) and LS-treated for 24, 48, and 72 h, and leaves were collected. The anti-ATG8a antibodies were used for immunoblotting. (E) Detection of free GFP generated from transgenic lines expressing GFP-ATG8e in WT, atg5-1 backgrounds before and after LS treatment. Four-wk-old plant samples were collected at 0, 12, 24, and 48 h after treatment. The anti-GFP antibodies were used for protein blotting analysis. The GFP-ATG8e fusion and free GFP form were indicated on the right. Coomassie blue–stained total proteins are shown on the right (D) or below the blots (E) to indicate the amount of protein loaded per lane.
Mentions: To assess the cellular function of autophagy in the submergence response, we characterized 4 autophagy-deficient mutants, atg2-1, atg5-1, atg7-3, and atg10-1, from the SALK and SAIL T-DNA insertion pools (Figs. S2 and S3) and tested their responses to submergence. The 4-wk-old atg mutants showed few phenotypic differences to the wild type under normal growth conditions. When the plants were LS-treated for 6 d or DS-treated for 2 d, all atg mutants displayed enhanced sensitivity to both treatments (Fig. 2A; Fig. S4A), while 2-d dark treatment alone did not cause obvious phenotypic differences between the wild type and atg mutants (Fig. S4A). Following recovery for 6 d, the atg mutants showed significant hypersensitivity to submergence under LS and DS conditions, in comparison to the wild-type control, as shown by calculating the dry weights and survival rates of the plants (Fig. 2A, B and C; Fig. S4A and S4B). Moreover, when the plants were treated with LS for various times, we clearly observed damage in the atg mutant leaves at 3 d after treatment in comparison to the wild type, which showed little damage (Fig. S5).Figure 2.

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