title: The Rab GTPase RabG3b functions in autophagy and contributes to tracheary element differentiation in Arabidopsis.
abstract: The tracheary elements (TEs) of the xylem serve as the water-conducting vessels of the plant vascular system. To achieve this, TEs undergo secondary cell wall thickening and cell death, during which the cell contents are completely removed. Cell death of TEs is a typical example of developmental programmed cell death that has been suggested to be autophagic. However, little evidence of autophagy in TE differentiation has been provided. The present study demonstrates that the small GTP binding protein RabG3b plays a role in TE differentiation through its function in autophagy. Differentiating wild type TE cells were found to undergo autophagy in an Arabidopsis culture system. Both autophagy and TE formation were significantly stimulated by overexpression of a constitutively active mutant (RabG3bCA), and were inhibited in transgenic plants overexpressing a dominant negative mutant (RabG3bDN) or RabG3b RNAi (RabG3bRNAi), a brassinosteroid insensitive mutant bri1-301, and an autophagy mutant atg5-1. Taken together, our results suggest that autophagy occurs during TE differentiation, and that RabG3b, as a component of autophagy, regulates TE differentiation.
authors.affiliation: School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea RIKEN Plant Science Center, Yokohama 230-0045, Japan.
authors.forename: Soon Il
authors.initials: SI
authors.lastname: Kwon
authors.forename: Hong Joo
authors.initials: HJ
authors.lastname: Cho
authors.forename: Jin Hee
authors.initials: JH
authors.lastname: Jung
authors.forename: Kohki
authors.initials: K
authors.lastname: Yoshimoto
authors.forename: Ken
authors.initials: K
authors.lastname: Shirasu
authors.forename: Ohkmae K
authors.initials: OK
authors.lastname: Park
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001343:Autophagy; D002454:Cell Differentiation; D018506:Gene Expression Regulation, Plant; D055785:Gene Knockdown Techniques; D030821:Plants, Genetically Modified / Q000166:cytology / Q000201:enzymology / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D052584:Xylem / Q000166:cytology; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D018749:RNA, Plant; C556156:RabG3b protein, Arabidopsis; D020691:rab GTP-Binding Proteins