title: Plant peroxisomes are degraded by starvation-induced and constitutive autophagy in tobacco BY-2 suspension-cultured cells.
abstract: Very recently, autophagy has been recognized as an important degradation pathway for quality control of peroxisomes in Arabidopsis plants. To further characterize the role of autophagy in plant peroxisome degradation, we generated stable transgenic suspension-cultured cell lines of heterotrophic Nicotiana tabacum L. cv. Bright Yellow 2 expressing a peroxisome-targeted version of enhanced yellow fluorescent protein. Indeed, this cell line model system proved advantageous for detailed cytological analyses of autophagy stages and for quantification of cellular peroxisome pools under different culturing conditions and upon inhibitor applications. Complementary biochemical, cytological, and pharmacological analyses provided convincing evidence for peroxisome degradation by bulk autophagy during carbohydrate starvation. This degradation was slowed down by the inhibitor of autophagy, 3-methyladenine (3-MA), but the 3-MA effect ceased at advanced stages of starvation, indicating that another degradation mechanism for peroxisomes might have taken over. 3-MA also caused an increase particularly in peroxisomal proteins and cellular peroxisome numbers when applied under nutrient-rich conditions in the logarithmic growth phase, suggesting a high turnover rate for peroxisomes by basal autophagy under non-stress conditions. Together, our data demonstrate that a great fraction of the peroxisome pool is subject to extensive autophagy-mediated turnover under both nutrient starvation and optimal growth conditions. Our analyses of the cellular pool size of peroxisomes provide a new tool for quantitative investigations of the role of plant peroxisomes in reactive oxygen species metabolism.
authors.affiliation: Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-Universität Göttingen Göttingen, Germany ; Komarov Botanical Institute, Russian Academy of Sciences, Laboratory of Plant Ecological Physiology Saint Petersburg, Russia.
authors.forename: Olga V
authors.initials: OV
authors.lastname: Voitsekhovskaja
authors.affiliation: Abteilung Pflanzenbiotechnologie, Fraunhofer-Institut für Molekularbiologie und Angewandte Oekologie Aachen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schiermeyer
authors.affiliation: Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-Universität Göttingen Göttingen, Germany ; Institute for Mathematics and Natural Sciences, Faculty of Science and Technology, Centre for Organelle Research, University of Stavanger Stavanger, Norway ; Faculty of Mathematics, Informatics and Natural Sciences, Biocentre Klein Flottbek, University of Hamburg Hamburg, Germany.
authors.forename: Sigrun
authors.initials: S
authors.lastname: Reumann
keywords: autophagy; cellular peroxisome pool; organelle degradation; peroxisome; pexophagy; tobacco BY-2 cells