title: The DNA-binding protease, CND41, and the degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase in senescent leaves of tobacco.
abstract: Plastids bear their own genome, organized into DNA-protein complexes (nucleoids). Recently, we identified a DNA-binding protease (CND41) in the chloroplast nucleoids of cultured tobacco (Nicotiana tabacum L.) cells. In this study, we examine the biochemical function of this novel DNA-binding protease, particularly in senescent leaves, because antisense tobacco with a reduced amount of CND41 showed retarded senescence. Nitrogen-depletion experiments clearly showed that CND41 antisense tobacco maintained green leaves and constant protein levels, especially ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), throughout the whole plant, whereas wild-type tobacco showed marked senescence and the reduction of protein levels in the lower leaves. In vitro analyses confirmed that CND41 showed proteolytic activity at physiological pH when denatured Rubisco was used as the substrate. These results suggest that CND41 is involved in Rubisco degradation and the translocation of nitrogen during senescence. The possible regulation of protease activity of CND41 through DNA-binding is discussed.
authors.affiliation: Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, 606-8502 Kyoto, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kato
authors.forename: Shinya
authors.initials: S
authors.lastname: Murakami
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Chatani
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kondo
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakano
authors.forename: Akiho
authors.initials: A
authors.lastname: Yokota
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Sato
mesh_terms: D016922:Cellular Senescence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D007700:Kinetics; D009584:Nitrogen / Q000172:deficiency; D018515:Plant Leaves / Q000254:growth & development* / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*; D014026:Nicotiana / Q000254:growth & development* / Q000378:metabolism
chemical_list: C108994:CND41 protein, Nicotiana tabacum; D004268:DNA-Binding Proteins; D010940:Plant Proteins; D012273:Ribulose-Bisphosphate Carboxylase; D009584:Nitrogen