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Unformatted text preview: Agrobacterium tumefaciens and Plant Cell Interactions and Activities Required for Interkingdom Macromolecular Transfer Colleen A. McCullen 1 , 2 and Andrew N. Binns 1 1 Department of Biology and Plant Sciences Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018; email: firstname.lastname@example.org 2 Current address: National Institutes of Health, Bethesda, Maryland 20892 Annu. Rev. Cell Dev. Biol. 2006. 22:10127 First published online as a Review in Advance on May 18, 2006 The Annual Review of Cell and Developmental Biology is online at http://cellbio.annualreviews.org This articles doi: 10.1146/annurev.cellbio.22.011105.102022 Copyright c 2006 by Annual Reviews. All rights reserved 1081-0706/06/1110-0101$20.00 Key Words virA- virG two-component system, signal integration, type IV secretion, VirB complex Abstract Host recognition and macromolecular transfer of virulence- mediating effectors represent critical steps in the successful trans- formation of plant cells by Agrobacterium tumefaciens . This review focuses on bacterial and plant-encoded components that interact to mediate these two processes. First, we examine the means by which Agrobacterium recognizes the host, via both diffusible plant-derived chemicals and cell-cell contact, with emphasis on the mechanisms by which multiple host signals are recognized and activate the viru- lence process. Second, we characterize the recognition and transfer of protein and protein-DNA complexes through the bacterial and plant cell membrane and wall barriers, emphasizing the central role of a type IV secretion systemthe VirB complexin this process. 101 A n n u . R e v . C e l l D e v . B i o l . 2 6 . 2 2 : 1 1- 1 2 7 . D o w n l o a d e d f r o m a r j o u r n a l s . a n n u a l r e v i e w s . o r g b y U N I V E R S I T Y O F F L O R I D A o n 2 / 1 3 / 7 . F o r p e r s o n a l u s e o n l y . Tumor-inducing (Ti) plasmid: large plasmid found in virulent strains of A. tumefaciens that encodes several of the proteins required for tumorigenesis Transferred DNA (T-DNA): region of the Ti plasmid of A. tumefaciens between 23 bp direct repeats processed into single-stranded form and transported into host plant cells during infection Opine: sugaramino acid conjugates synthesized by A. tumefaciens transformed plant cells that can be metabolized by A. tumefaciens cells carrying a Ti plasmid Contents INTRODUCTION. . . . . . . . . . . . . . . . . 102 HOST RECOGNITION . . . . . . . . . . . 103 Virulence Gene Expression . . . . . . . 104 Attachment of Agrobacteria to Host Cells. . . . . . . . . . . . . . . . . . 110 MACROMOLECULAR TRANSPORT . . . . . . . . . . . . . . . . . . . 111 Targeting of Substrates . . . . . . . . . . . 111 Mechanism of Export. . . . . . . . . . . . . 113 Substrate Entry into Host Cells . . . 116 INTRODUCTION Agrobacterium tumefaciens is a broad-host- range pathogen, initiating tumors on plants of most dicotyledonous genera and some mono- cots as well (DeCleene & DeLay 1976). Thesecots as well (DeCleene & DeLay 1976)....
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