NBR1-Mediated Selective Autophagy Targets Insoluble Ubiquitinated Protein Aggregates in Plant Stress Responses


Plant autophagy plays an important role in delaying senescence, nutrient recycling, and stress responses. Functional analysis of plant autophagy has almost exclusively focused on the proteins required for the core process of autophagosome assembly, but little is known about the proteins involved in other important processes of autophagy, including autophagy cargo recognition and sequestration. In this study, we report functional genetic analysis of Arabidopsis NBR1, a homolog of mammalian autophagy cargo adaptors P62 and NBR1. We isolated two nbr1 knockout mutants and discovered that they displayed some but not all of the phenotypes of autophagy-deficient atg5 and atg7 mutants. Like ATG5 and ATG7, NBR1 is important for plant tolerance to heat, oxidative, salt, and drought stresses. The role of NBR1 in plant tolerance to these abiotic stresses is dependent on its interaction with ATG8. Unlike ATG5 and ATG7, however, NBR1 is dispensable in age- and darkness-induced senescence and in resistance to a necrotrophic pathogen. A selective role of NBR1 in plant responses to specific abiotic stresses suggest that plant autophagy in diverse biological processes operates through multiple cargo recognition and delivery systems. The compromised heat tolerance of atg5, atg7, and nbr1 mutants was associated with increased accumulation of insoluble, detergent-resistant proteins that were highly ubiquitinated under heat stress. NBR1, which contains an ubiquitin-binding domain, also accumulated to high levels with an increasing enrichment in the insoluble protein fraction in the autophagy-deficient mutants under heat stress. These results suggest that NBR1-mediated autophagy targets ubiquitinated protein aggregates most likely derived from denatured or otherwise damaged nonnative proteins generated under stress conditions.


Vyšlo v časopise: NBR1-Mediated Selective Autophagy Targets Insoluble Ubiquitinated Protein Aggregates in Plant Stress Responses. PLoS Genet 9(1): e32767. doi:10.1371/journal.pgen.1003196
Kategorie: Research Article
prolekare.web.journal.doi_sk: 10.1371/journal.pgen.1003196

Souhrn

Plant autophagy plays an important role in delaying senescence, nutrient recycling, and stress responses. Functional analysis of plant autophagy has almost exclusively focused on the proteins required for the core process of autophagosome assembly, but little is known about the proteins involved in other important processes of autophagy, including autophagy cargo recognition and sequestration. In this study, we report functional genetic analysis of Arabidopsis NBR1, a homolog of mammalian autophagy cargo adaptors P62 and NBR1. We isolated two nbr1 knockout mutants and discovered that they displayed some but not all of the phenotypes of autophagy-deficient atg5 and atg7 mutants. Like ATG5 and ATG7, NBR1 is important for plant tolerance to heat, oxidative, salt, and drought stresses. The role of NBR1 in plant tolerance to these abiotic stresses is dependent on its interaction with ATG8. Unlike ATG5 and ATG7, however, NBR1 is dispensable in age- and darkness-induced senescence and in resistance to a necrotrophic pathogen. A selective role of NBR1 in plant responses to specific abiotic stresses suggest that plant autophagy in diverse biological processes operates through multiple cargo recognition and delivery systems. The compromised heat tolerance of atg5, atg7, and nbr1 mutants was associated with increased accumulation of insoluble, detergent-resistant proteins that were highly ubiquitinated under heat stress. NBR1, which contains an ubiquitin-binding domain, also accumulated to high levels with an increasing enrichment in the insoluble protein fraction in the autophagy-deficient mutants under heat stress. These results suggest that NBR1-mediated autophagy targets ubiquitinated protein aggregates most likely derived from denatured or otherwise damaged nonnative proteins generated under stress conditions.


Zdroje

1. KlionskyDJ (2005) Autophagy. Curr Biol 15: R282–283.

2. KlionskyDJ (2005) The molecular machinery of autophagy: unanswered questions. J Cell Sci 118: 7–18.

3. XieZ, KlionskyDJ (2007) Autophagosome formation: core machinery and adaptations. Nat Cell Biol 9: 1102–1109.

4. LevineB, YuanJ (2005) Autophagy in cell death: an innocent convict? J Clin Invest 115: 2679–2688.

5. MizushimaN (2007) Autophagy: process and function. Genes Dev 21: 2861–2873.

6. JohansenT, LamarkT (2011) Selective autophagy mediated by autophagic adapter proteins. Autophagy 7: 279–296.

7. NovakI, KirkinV, McEwanDG, ZhangJ, WildP, et al. (2010) Nix is a selective autophagy receptor for mitochondrial clearance. EMBO Reports 11: 45–51.

8. ThurstonTL, RyzhakovG, BloorS, von MuhlinenN, RandowF (2009) The TBK1 adaptor and autophagy receptor NDP52 restricts the proliferation of ubiquitin-coated bacteria. Nature Immunol 10: 1215–1221.

9. ZhengYT, ShahnazariS, BrechA, LamarkT, JohansenT, et al. (2009) The adaptor protein p62/SQSTM1 targets invading bacteria to the autophagy pathway. J Immunol 183: 5909–5916.

10. KwonSI, ParkOK (2008) Autophagy in plants. J Plant Biol 51: 313–320.

11. ChungT, SuttangkakulA, VierstraRD (2009) The ATG autophagic conjugation system in maize: ATG transcripts and abundance of the ATG8-lipid adduct are regulated by development and nutrient availability. Plant Physiol 149: 220–234.

12. LiuY, SchiffM, CzymmekK, TalloczyZ, LevineB, et al. (2005) Autophagy regulates programmed cell death during the plant innate immune response. Cell 121: 567–577.

13. ShinJH, YoshimotoK, OhsumiY, JeonJS, AnG (2009) OsATG10b, an autophagosome component, is needed for cell survival against oxidative stresses in rice. Molecules and Cells 27: 67–74.

14. SuW, MaH, LiuC, WuJ, YangJ (2006) Identification and characterization of two rice autophagy associated genes, OsAtg8 and OsAtg4. Mol Biol Reports 33: 273–278.

15. ThompsonAR, DoellingJH, SuttangkakulA, VierstraRD (2005) Autophagic nutrient recycling in Arabidopsis directed by the ATG8 and ATG12 conjugation pathways. Plant Physiol 138: 2097–2110.

16. XiongY, ContentoAL, BasshamDC (2005) AtATG18a is required for the formation of autophagosomes during nutrient stress and senescence in Arabidopsis thaliana. Plant J 42: 535–546.

17. XiongY, ContentoAL, BasshamDC (2007) Disruption of autophagy results in constitutive oxidative stress in Arabidopsis. Autophagy 3: 257–258.

18. XiongY, ContentoAL, NguyenPQ, BasshamDC (2007) Degradation of oxidized proteins by autophagy during oxidative stress in Arabidopsis. Plant Physiol 143: 291–299.

19. DoellingJH, WalkerJM, FriedmanEM, ThompsonAR, VierstraRD (2002) The APG8/12-activating enzyme APG7 is required for proper nutrient recycling and senescence in Arabidopsis thaliana. J Biol Chem 277: 33105–33114.

20. HanaokaH, NodaT, ShiranoY, KatoT, HayashiH, et al. (2002) Leaf senescence and starvation-induced chlorosis are accelerated by the disruption of an Arabidopsis autophagy gene. Plant Physiol 129: 1181–1193.

21. IshidaH, YoshimotoK, IzumiM, ReisenD, YanoY, et al. (2008) Mobilization of rubisco and stroma-localized fluorescent proteins of chloroplasts to the vacuole by an ATG gene-dependent autophagic process. Plant Physiol 148: 142–155.

22. PatelS, Dinesh-KumarSP (2008) Arabidopsis ATG6 is required to limit the pathogen-associated cell death response. Autophagy 4: 20–27.

23. ZhengZ, QamarSA, ChenZ, MengisteT (2006) Arabidopsis WRKY33 transcription factor is required for resistance to necrotrophic fungal pathogens. Plant J 48: 592–605.

24. LaiZ, WangF, ZhengZ, FanB, ChenZ (2011) A critical role of autophagy in plant resistance to necrotrophic fungal pathogens. Plant J 66: 953–968.

25. LenzHD, HallerE, MelzerE, KoberK, WursterK, et al. (2011) Autophagy differentially controls plant basal immunity to biotrophic and necrotrophic pathogens. Plant J 66: 818–830.

26. LiuY, XiongY, BasshamDC (2009) Autophagy is required for tolerance of drought and salt stress in plants. Autophagy 5: 954–963.

27. SlavikovaS, UfazS, Avin-WittenbergT, LevanonyH, GaliliG (2008) An autophagy-associated Atg8 protein is involved in the responses of Arabidopsis seedlings to hormonal controls and abiotic stresses. J Exp Bot 59: 4029–4043.

28. SvenningS, LamarkT, KrauseK, JohansenT (2011) Plant NBR1 is a selective autophagy substrate and a functional hybrid of the mammalian autophagic adapters NBR1 and p62/SQSTM1. Autophagy 7: 993–1010.

29. KirisakoT, IchimuraY, OkadaH, KabeyaY, MizushimaN, et al. (2000) The reversible modification regulates the membrane-binding state of Apg8/Aut7 essential for autophagy and the cytoplasm to vacuole targeting pathway. J Cell Biol 151: 263–276.

30. HonigA, Avin-WittenbergT, UfazS, GaliliG (2012) A New Type of Compartment, Defined by Plant-Specific Atg8-Interacting Proteins, Is Induced upon Exposure of Arabidopsis Plants to Carbon Starvation. Plant Cell 24: 288–303.

31. Zientara-RytterK, LukomskaJ, MoniuszkoG, GwozdeckiR, SurowieckiP, et al. (2011) Identification and functional analysis of Joka2, a tobacco member of the family of selective autophagy cargo receptors. Autophagy 7: 1145–1158.

32. SungDY, KaplanF, LeeKJ, GuyCL (2003) Acquired tolerance to temperature extremes. Trends Plant Sci 8: 179–187.

33. ContentoAL, XiongY, BasshamDC (2005) Visualization of autophagy in Arabidopsis using the fluorescent dye monodansylcadaverine and a GFP-AtATG8e fusion protein. Plant J 42: 598–608.

34. YoshimotoK, HanaokaH, SatoS, KatoT, TabataS, et al. (2004) Processing of ATG8s, ubiquitin-like proteins, and their deconjugation by ATG4s are essential for plant autophagy. Plant Cell 16: 2967–2983.

35. TangY, WenX, LuQ, YangZ, ChengZ, et al. (2007) Heat stress induces an aggregation of the light-harvesting complex of photosystem II in spinach plants. Plant Physiol 143: 629–638.

36. PastenesC, HortonP (1996) Effect of High Temperature on Photosynthesis in Beans (II. CO2 Assimilation and Metabolite Contents). Plant Physiol 112: 1253–1260.

37. PastenesC, HortonP (1996) Effect of High Temperature on Photosynthesis in Beans (I. Oxygen Evolution and Chlorophyll Fluorescence). Plant Physiol 112: 1245–1251.

38. YoshimotoK, JikumaruY, KamiyaY, KusanoM, ConsonniC, et al. (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.

39. XingD, ChenZ (2006) Effects of mutations and constitutive overexpression of EDS1 and PAD4 on plant resistance to different types of microbial pathogens. Plant Sci 171: 251–262.

40. Calvo-GarridoJ, EscalanteR (2010) Autophagy dysfunction and ubiquitin-positive protein aggregates in Dictyostelium cells lacking Vmp1. Autophagy 6: 100–109.

41. WahidA, GelaniS, AshrafM, FooladMR (2007) Heat tolerance in plants: an overview. Environ Exp Bot 61: 199–223.

42. GamerdingerM, CarraS, BehlC (2011) Emerging roles of molecular chaperones and co-chaperones in selective autophagy: focus on BAG proteins. J Mol Med 89: 1175–1182.

43. NandiD, TahilianiP, KumarA, ChanduD (2006) The ubiquitin-proteasome system. J Biosci 31: 137–155.

44. BenceNF, SampatRM, KopitoRR (2001) Impairment of the ubiquitin-proteasome system by protein aggregation. Science 292: 1552–1555.

45. KraftC, PeterM, HofmannK (2010) Selective autophagy: ubiquitin-mediated recognition and beyond. Nature Cell Biol 12: 836–841.

46. LeeJY, KogaH, KawaguchiY, TangW, WongE, et al. (2010) HDAC6 controls autophagosome maturation essential for ubiquitin-selective quality-control autophagy. EMBO J 29: 969–980.

47. YaoTP (2010) The role of ubiquitin in autophagy-dependent protein aggregate processing. Genes & Cancer 1: 779–786.

48. GlazebrookJ (2005) Contrasting Mechanisms of Defense Against Biotrophic and Necrotrophic Pathogens. Annu Rev Phytopathol 43: 205–227.

49. van KanJA (2006) Licensed to kill: the lifestyle of a necrotrophic plant pathogen. Trends Plant Sci 11: 247–253.

50. CuiX, FanB, ScholzJ, ChenZ (2007) Roles of Arabidopsis Cyclin-Dependent Kinase C Complexes in Cauliflower Mosaic Virus Infection, Plant Growth, and Development. Plant Cell 19: 1388–1402.

51. LivakKJ, SchmittgenTD (2001) Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method. Methods 25: 402–408.

52. HuangJ, GuM, LaiZ, FanB, ShiK, et al. (2010) Functional analysis of the Arabidopsis PAL gene family in plant growth, development, and response to environmental stress. Plant Physiol 153: 1526–1538.

53. CloughSJ, BentAF (1998) Floral dip: a simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana. Plant J 16: 735–743.

54. HongSW, LeeU, VierlingE (2003) Arabidopsis hot mutants define multiple functions required for acclimation to high temperatures. Plant Physiol 132: 757–767.

55. LaiZ, LiY, WangF, ChengY, FanB, et al. (2011) Arabidopsis sigma factor binding proteins are activators of the WRKY33 transcription factor in plant defense. Plant Cell 23: 3824–3841.

56. RubioV, ShenY, SaijoY, LiuY, GusmaroliG, et al. (2005) An alternative tandem affinity purification strategy applied to Arabidopsis protein complex isolation. Plant J 41: 767–778.

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Genetika Reprodukčná medicína

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PLOS Genetics


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