title: TRAF Family Proteins Regulate Autophagy Dynamics by Modulating AUTOPHAGY PROTEIN6 Stability in Arabidopsis.
abstract: Eukaryotic cells use autophagy to recycle cellular components. During autophagy, autophagosomes deliver cytoplasmic contents to the vacuole or lysosome for breakdown. Mammalian cells regulate the dynamics of autophagy via ubiquitin-mediated proteolysis of autophagy proteins. Here, we show that theArabidopsis thalianaTumor necrosis factor Receptor-Associated Factor (TRAF) family proteins TRAF1a and TRAF1b (previously named MUSE14 and MUSE13, respectively) help regulate autophagy via ubiquitination. Upon starvation, cytoplasmic TRAF1a and TRAF1b translocated to autophagosomes. Knockouttraf1a/blines showed reduced tolerance to nutrient deficiency, increased salicylic acid and reactive oxygen species levels, and constitutive cell death in rosettes, resembling the phenotypes of autophagy-defective mutants. Starvation-activated autophagosome accumulation decreased intraf1a/broot cells, indicating that TRAF1a and TRAF1b function redundantly in regulating autophagosome formation. TRAF1a and TRAF1b interacted in planta with ATG6 and the RING finger E3 ligases SINAT1, SINAT2, and SINAT6 (with a truncated RING-finger domain). SINAT1 and SINAT2 require the presence of TRAF1a and TRAF1b to ubiquitinate and destabilize AUTOPHAGY PROTEIN6 (ATG6) in vivo. Conversely, starvation-induced SINAT6 reduced SINAT1- and SINAT2-mediated ubiquitination and degradation of ATG6. Consistently,SINAT1/SINAT2andSINAT6knockout mutants exhibited increased tolerance and sensitivity, respectively, to nutrient starvation. Therefore, TRAF1a and TRAF1b function as molecular adaptors that help regulate autophagy by modulating ATG6 stability in Arabidopsis.
authors.affiliation: 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 510275, P.R. China.
authors.forename: Hua
authors.initials: H
authors.lastname: Qi
authors.affiliation: 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 510275, P.R. China.
authors.forename: Fan-Nv
authors.initials: FN
authors.lastname: Xia
authors.affiliation: 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 510275, P.R. China.
authors.forename: Li-Juan
authors.initials: LJ
authors.lastname: Xie
authors.affiliation: 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 510275, P.R. China.
authors.forename: Lu-Jun
authors.initials: LJ
authors.lastname: Yu
authors.affiliation: 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 510275, P.R. China.
authors.forename: Qin-Fang
authors.initials: QF
authors.lastname: Chen
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, P.R. China.
authors.forename: Xiao-Hong
authors.identifier: http://orcid.org/0000-0002-2480-8210
authors.initials: XH
authors.lastname: Zhuang
authors.affiliation: State Key Laboratory of Plant Genomics, National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, P.R. China.
authors.forename: Qian
authors.identifier: http://orcid.org/0000-0002-7706-4542
authors.initials: Q
authors.lastname: Wang
authors.affiliation: College of Life Sciences, South China Agricultural University, Guangzhou 510642, P.R. China.
authors.forename: Faqiang
authors.identifier: http://orcid.org/0000-0003-4117-2450
authors.initials: F
authors.lastname: Li
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, P.R. China.
authors.forename: Liwen
authors.initials: L
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Plant Genomics, National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, P.R. China.
authors.forename: Qi
authors.identifier: http://orcid.org/0000-0002-8262-9093
authors.initials: Q
authors.lastname: Xie
authors.affiliation: 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 510275, P.R. China xiaoshi3@mail.sysu.edu.cn.
authors.forename: Shi
authors.identifier: http://orcid.org/0000-0002-6632-8952
authors.initials: S
authors.lastname: Xiao
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001343:Autophagy / Q000235:genetics / Q000502:physiology; D000071186:Beclin-1 / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D047990:TNF Receptor-Associated Factor 1 / Q000235:genetics / Q000378:metabolism; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D000071186:Beclin-1; D002352:Carrier Proteins; C525663:SINAT2 protein, Arabidopsis; D047990:TNF Receptor-Associated Factor 1; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins; C519561:beclin 1 protein, Arabidopsis; C000607353:SINAT1 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases