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Science 333 (6046): 1141-1144

Copyright © 2011 by the American Association for the Advancement of Science

Chaperonins Facilitate KNOTTED1 Cell-to-Cell Trafficking and Stem Cell Function

Xianfeng Morgan Xu, Jing Wang, Zhenyu Xuan,* Alexander Goldshmidt, Philippa G. M. Borrill,{dagger} Nisha Hariharan,{ddagger} Jae Yean Kim,§ David Jackson||

Abstract: Cell-to-cell communication in plants includes the selective trafficking of transcription factors and other signals through plasmodesmata. The KNOTTED1 (KN1) homeobox (KNOX) family transcription factors, which use this pathway, are essential for stem cell establishment and/or maintenance. Here we show that KN1 trafficking requires the chaperonin complex, which belongs to a group of cytosolic chaperones that fold specific substrate proteins. Genetic and physical interaction data show a functional relevance for chaperonins in KNOX family-dependent stem cell maintenance. Furthermore, tissue-specific complementation assays indicate a mechanistic basis for chaperonin function during the posttranslocational refolding process. Our study shows that chaperonins are essential for the cell-to-cell trafficking of a subset of mobile transcription factors and demonstrates the importance of chaperonin-dependent protein trafficking for plant stem cell function.

Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.

* Present address: Department of Molecular and Cell Biology, Center for Systems Biology, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080, USA.

{dagger} Present address: John Innes Centre, Norwich Research Park, Norwich, Norfolk NR4 7UH, UK.

{ddagger} Present address: Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720–3200, USA.

§ Present address: Division of Applied Life Science (BK21/World Class University program), Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju 660-701, Korea.

||To whom correspondence should be addressed. E-mail: jacksond{at}

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