Agrobacterium tumefaciens and Plant Cell Interactions and Activities Required for Interkingdom Macromolecular Transfer

Abstract

Host recognition and macromolecular transfer of virulence-mediating effectors represent critical steps in the successful transformation 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 virulence 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 system-the VirB complex-in this process.

Bacteria are small but not stupid: cognition, natural genetic engineering and socio-bacteriology

“…The ability to take over the processes of eukaryotic cells is especially relevant to a discussion of the informatic capacities of bacteria. Two well-studied examples of these takeovers include Agrobacterium T-DNA transfer into plant nuclei to create tumor cells that feed the oncogenic bacterial population (McCullen & Binns, 2006) and injection of proteins to reorganize mammalian host cell function and facilitate intracellular pathogensis (Mota & Cornelis, 2005). The T-DNA encodes plant hormones that redirect growth control as well as biosynthetic enzymes that create compounds uniquely metabolized by Agrobacterium.…”

The plant signal salicylic acid shuts down expression of the vir regulon and activates quormone-quenching genes in Agrobacterium

“…In addition to the Ti plasmid-encoded vir genes, a number of chromosomally encoded genes, termed chv, are also important for virulence (1,3). These genes include chvA and chvB, which are required for the attachment of Agrobacterium to plant cells.…”

“…These genes include chvA and chvB, which are required for the attachment of Agrobacterium to plant cells. One of the most intensively studied is chvE (1). The ChvE protein binds a number of different sugars in the rhizosphere and then interacts with the periplasmic region of the VirA protein.…”

“…The ChvE protein binds a number of different sugars in the rhizosphere and then interacts with the periplasmic region of the VirA protein. The ChvG/I two-component system is required for virG gene expression and for growth under acidic conditions (1). None of the chromosomally encoded chv genes has a vir box in its upstream sequences, nor are they regulated by the VirA/G system.…”

Interaction of the Agrobacterium tumefaciens virulence protein VirD2 with histones

“…Agrobacterium tumefaciens is a Gram-negative soil bacterium that genetically transforms dicotyledonous plants causing crown gall disease (Smith & Townsend, 1907; for reviews, see Lacroix et al, 2006;McCullen & Binns, 2006;Pitzschke & Hirt, 2010;Gelvin, 2012). During the transformation a piece of DNA, referred to as T-DNA (transferred DNA), is transferred through a type IV secretion system into the plant cells.…”