title: Exocyst-Positive Organelles and Autophagosomes Are Distinct Organelles in Plants.
abstract: Autophagosomes are organelles that deliver cytosolic proteins for degradation in the vacuole of the cell. In contrast, exocyst-positive organelles (EXPO) deliver cytosolic proteins to the cell surface and therefore represent a form of unconventional protein secretion. Because both structures have two boundary membranes, it has been suggested that they may have been falsely treated as separate entities. Using suspension culture cells and root tissue cells of transgenic Arabidopsis (Arabidopsis thaliana) plants expressing either the EXPO marker Arabidopsis Exo70E2-GFP or the autophagosome marker yellow fluorescent protein (YFP)-autophagy-related gene 8e/f (ATG8e/f), and using specific antibodies against Exo70E2 and ATG8, we have now established that, in normally growing cells, EXPO and autophagosomes are distinct from one another. However, when cells/roots are subjected to autophagy induction, EXPO as well as autophagosomes fuse with the vacuole. In the presence of concanamycin A, the punctate fluorescent signals from both organelles inside the vacuole remain visible for hours and overlap to a significant degree. Tonoplast staining with FM4-64/YFP-Rab7-like GTPase/YFP-vesicle-associated membrane protein711 confirmed the internalization of tonoplast membrane concomitant with the sequestration of EXPO and autophagosomes. This suggests that EXPO and autophagosomes may be related to one another; however, whereas induction of autophagy led to an increase in the amount of ATG8 recruited to membranes, Exo70E2 did not respond in a similar manner.
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.).
authors.forename: Youshun
authors.initials: Y
authors.lastname: Lin
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.).
authors.forename: Yu
authors.identifier: http://orcid.org/0000-0002-3688-7294
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.).
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.).
authors.forename: Jinbo
authors.initials: J
authors.lastname: Shen
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.).
authors.forename: Chun Hong
authors.identifier: http://orcid.org/0000-0003-1244-5990
authors.initials: CH
authors.lastname: Kung
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.).
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Zhuang
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.).
authors.forename: Yong
authors.initials: Y
authors.lastname: Cui
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.).
authors.forename: Zhao
authors.initials: Z
authors.lastname: Yin
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.).
authors.forename: Yiji
authors.initials: Y
authors.lastname: Xia
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.).
authors.forename: Hongxuan
authors.identifier: http://orcid.org/0000-0002-2818-023X
authors.initials: H
authors.lastname: Lin
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.).
authors.forename: David G
authors.initials: DG
authors.lastname: Robinson
authors.affiliation: Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.) ljiang@cuhk.edu.hk.
authors.forename: Liwen
authors.initials: L
authors.lastname: Jiang
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001343:Autophagy; D000071190:Autophagy-Related Protein 8 Family; D003593:Cytoplasm / Q000378:metabolism; D049452:Green Fluorescent Proteins; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D010588:Phagosomes / Q000378:metabolism*; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D014617:Vacuoles / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C000597073:ATG8 protein, Arabidopsis; D029681:Arabidopsis Proteins; D000071190:Autophagy-Related Protein 8 Family; C000592430:Exo70E2 protein, Arabidopsis; D008869:Microtubule-Associated Proteins; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins