Abstract
Key message
This study reveals that plant roots show a rapid termination of autophagy induction, offering a plant model for studying how excessive autophagy is deterred.
Abstract
In eukaryotes, autophagy is an intracellular mechanism that is important for recycling nutrients by degrading various macromolecules and organelles in vacuoles and lysosomes. Autophagy is induced when the nutrient supply to plant cells is limited. The protein kinase target of rapamycin (TOR) complex negatively regulates autophagy when nutrients are present in adequate amounts. The TOR inhibitor AZD8055 is an autophagy inducer that is useful for studying starvation-induced autophagy in plant cells. The mechanism by which AZD8055 increases the autophagic flux in plant cells has not been studied in detail. Here, we show that AZD8055-induced autophagy requires phosphatidylinositol 3-kinase activity and canonical AUTOPHAGY-RELATED (ATG) genes in Arabidopsis thaliana. Autophagic flux rapidly increased in seedlings treated with AZD8055. Unexpectedly, autophagy induction was transient in root cells and terminated earlier than in cotyledon cells. Transient induction is partly caused by a temporary effect of AZD8055 on phagophore initiation. These findings indicate a TOR-independent mechanism for terminating autophagy induction, thereby paving the way for elucidating how excess autophagy is prevented in plant roots.
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References
Antonioli M, Di Rienzo M, Piacentini M, Fimia GM (2017) Emerging mechanisms in initiating and terminating autophagy. Trends Biochem Sci 42:28–41
Bago R, Malik N, Munson MJ, Prescott AR, Davies P, Sommer E, Shpiro N, Ward R, Cross D, Ganley IG, Alessi DR (2014) Characterization of VPS34-IN1, a selective inhibitor of Vps34, reveals that the phosphatidylinositol 3-phosphate-binding SGK3 protein kinase is a downstream target of class III phosphoinositide 3-kinase. Biochem J 463:413–427
Chung T, Phillips AR, Vierstra RD (2010) ATG8 lipidation and ATG8-mediated autophagy in Arabidopsis require ATG12 expressed from the differentially controlled ATG12A and ATG12B loci. Plant J 62:483–493
Clough SJ, Bent AF (1998) Floral dip: a simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana. Plant J 16:735–743
Condon KJ, Sabatini DM (2019) Nutrient regulation of mTORC1 at a glance. J Cell Sci 132:jcs222570. doi: https://doi.org/10.1242/jcs.222570
Dauphinee AN, Cardoso C, Dalman K, Ohlsson JA, Fick SB, Robert S, Hicks GR, Bozhkov PV, Minina EA (2019) Chemical screening pipeline for identification of specific plant autophagy modulators. Plant Physiol 181:855–866
Doelling JH, Walker JM, Friedman EM, Thompson AR, Vierstra RD (2002) The APG8/12-activating enzyme APG7 is required for proper nutrient recycling and senescence in Arabidopsis thaliana. J Biol Chem 277:33105–33114
Dong P, Xiong F, Que Y, Wang K, Yu L, Li Z, Ren M (2015) Expression profiling and functional analysis reveals that TOR is a key player in regulating photosynthesis and phytohormone signaling pathways in Arabidopsis. Front Plant Sci 6:677
Grefen C, Donald N, Hashimoto K, Kudla J, Schumacher K, Blatt MR (2010) A ubiquitin-10 promoter-based vector set for fluorescent protein tagging facilitates temporal stability and native protein distribution in transient and stable expression studies. Plant J 64:355–365
Inoue Y, Suzuki T, Hattori M, Yoshimoto K, Ohsumi Y, Moriyasu Y (2006) AtATG genes, homologs of yeast autophagy genes, are involved in constitutive autophagy in Arabidopsis root tip cells. Plant Cell Physiol 47:1641–1652
Jung H, Kim JH, Shin KD, Kim J, Lee HN, Chung T (2017) Autophagic flux analysis of Arabidopsis seedlings exposed to salt stress. Journal of Plant Biology 60:199–206
Jung H, Lee HN, Marshall RS, Lomax AW, Yoon MJ, Kim J, Kim JH, Vierstra RD, Chung T (2020) Arabidopsis cargo receptor NBR1 mediates selective autophagy of defective proteins. J Exp Bot 71:73–89
Kang S, Shin KD, Kim JH, Chung T (2018) Autophagy-related (ATG) 11, ATG9 and the phosphatidylinositol 3-kinase control ATG2-mediated formation of autophagosomes in Arabidopsis. Plant Cell Rep 37:653–664
Kim J, Lee H, Lee HN, Kim SH, Shin KD, Chung T (2013) Autophagy-related proteins are required for degradation of peroxisomes in arabidopsis hypocotyls during seedling growth. Plant Cell 25:4956–4966
Kim JH, Jung H, Chung T (2020) Birth, growth, maturation, and demise of plant autophagic vesicles. J Plant Biol 63:155–164
Klionsky DJ, Abdelmohsen K, Abe A, et al. (2016) Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). Autophagy 12:1–222
Le Bars R, Marion J, Le Borgne R, Satiat-Jeunemaitre B, Bianchi MW (2014) ATG5 defines a phagophore domain connected to the endoplasmic reticulum during autophagosome formation in plants. Nat Commun 5:4121
Liu Q, Xu C, Kirubakaran S, Zhang X, Hur W, Liu Y, Kwiatkowski NP, Wang J, Westover KD, Gao P, Ercan D, Niepel M, Thoreen CC, Kang SA, Patricelli MP, Wang Y, Tupper T, Altabef A, Kawamura H, Held KD, Chou DM, Elledge SJ, Janne PA, Wong KK, Sabatini DM, Gray NS (2013) Characterization of Torin2, an ATP-competitive inhibitor of mTOR, ATM, and ATR. Cancer Res 73:2574–2586
Liu Y, Bassham DC (2010) TOR is a negative regulator of autophagy in Arabidopsis thaliana. PLoS One 5:e11883
Luo L, Zhang P, Zhu R, Fu J, Su J, Zheng J, Wang Z, Wang D, Gong Q (2017) Autophagy is rapidly induced by salt stress and is required for salt tolerance in arabidopsis. Front Plant Sci 8:1459
Maeda S, Otomo C, Otomo T (2019) The autophagic membrane tether ATG2A transfers lipids between membranes. Elife. https://doi.org/10.7554/eLife.45777
Marshall RS, Vierstra RD (2018) Autophagy: the master of bulk and selective recycling. Annu Rev Plant Biol 69:173–208
Marshall RS, Li F, Gemperline DC, Book AJ, Vierstra RD (2015) Autophagic degradation of the 26S proteasome is mediated by the dual ATG8/Ubiquitin receptor RPN10 in arabidopsis. Mol Cell 58:1053–1066
Osawa T, Kotani T, Kawaoka T, Hirata E, Suzuki K, Nakatogawa H, Ohsumi Y, Noda NN (2019) Atg2 mediates direct lipid transfer between membranes for autophagosome formation. Nat Struct Mol Biol 26:281–288
Rodriguez E, Chevalier J, Olsen J, Ansbol J, Kapousidou V, Zuo Z, Svenning S, Loefke C, Koemeda S, Drozdowskyj PS, Jez J, Durnberger G, Kuenzl F, Schutzbier M, Mechtler K, Ebstrup EN, Lolle S, Dagdas Y, Petersen M (2020) Autophagy mediates temporary reprogramming and dedifferentiation in plant somatic cells. EMBO J 39:e103315
Shin KD, Lee HN, Chung T (2014) A revised assay for monitoring autophagic flux in Arabidopsis thaliana reveals involvement of AUTOPHAGY-RELATED9 in autophagy. Mol Cells 37:399–405
Soto-Burgos J, Bassham DC (2017) SnRK1 activates autophagy via the TOR signaling pathway in Arabidopsis thaliana. PLoS One 12:e0182591
Suttangkakul A, Li F, Chung T, Vierstra RD (2011) The ATG1/ATG13 protein kinase complex is both a regulator and a target of autophagic recycling in Arabidopsis. Plant Cell 23:3761–3779
Thompson AR, Doelling JH, Suttangkakul A, Vierstra RD (2005) Autophagic nutrient recycling in Arabidopsis directed by the ATG8 and ATG12 conjugation pathways. Plant Physiol 138:2097–2110
Valverde DP, Yu S, Boggavarapu V, Kumar N, Lees JA, Walz T, Reinisch KM, Melia TJ (2019) ATG2 transports lipids to promote autophagosome biogenesis. J Cell Biol 218:1787–1798
Yoshimoto K, Hanaoka H, Sato S, Kato T, Tabata S, Noda T, Ohsumi Y (2004) Processing of ATG8s, ubiquitin-like proteins, and their deconjugation by ATG4s are essential for plant autophagy. Plant Cell 16:2967–2983
Yoshimoto K, Jikumaru Y, Kamiya Y, Kusano M, Consonni C, Panstruga R, Ohsumi Y, Shirasu K (2009) Autophagy negatively regulates cell death by controlling NPR1-dependent salicylic acid signaling during senescence and the innate immune response in Arabidopsis. Plant Cell 21:2914–2927
Yu L, McPhee CK, Zheng L, Mardones GA, Rong Y, Peng J, Mi N, Zhao Y, Liu Z, Wan F, Hailey DW, Oorschot V, Klumperman J, Baehrecke EH, Lenardo MJ (2010) Termination of autophagy and reformation of lysosomes regulated by mTOR. Nature 465:942–946
Zhuang X, Wang H, Lam SK, Gao C, Wang X, Cai Y, Jiang L (2013) A BAR-domain protein SH3P2, which binds to phosphatidylinositol 3-phosphate and ATG8, regulates autophagosome formation in Arabidopsis. Plant Cell 25:4596–4615
Acknowledgements
We would like to thank Dr. Richard Vierstra for providing transgenic plants expressing Pro35S:GFP-ATG8A.
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This work was supported by a 2-Year Research Grant from the Pusan National University to TC, as well as by BK21 Four Program of Pusan National University to JHK.
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TC conceived and designed the study. JHK, HJ, and YEC conducted the experiments and analyzed the data. TC and JHK wrote the manuscript with support from HJ and YEC.
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Communicated by Youn-Il Park.
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Kim, J.H., Jung, H., Choi, Y.E. et al. Autophagy inducers lead to transient accumulation of autophagosomes in Arabidopsis roots. Plant Cell Rep 41, 463–471 (2022). https://doi.org/10.1007/s00299-021-02821-2
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DOI: https://doi.org/10.1007/s00299-021-02821-2