Plant responses to Agrobacterium tumefaciens and crown gall development

Abstract

Agrobacterium tumefaciens causes crown gall disease on various plant species by introducing its T-DNA into the genome. Therefore, Agrobacterium has been extensively studied both as a pathogen and an important biotechnological tool. The infection process involves the transfer of T-DNA and virulence proteins into the plant cell. At that time the gene expression patterns of host plants differ depending on the Agrobacterium strain, plant species and cell-type used. Later on, integration of the T-DNA into the plant host genome, expression of the encoded oncogenes, and increase in phytohormone levels induce a fundamental reprogramming of the transformed cells. This results in their proliferation and finally formation of plant tumors. The process of reprogramming is accompanied by altered gene expression, morphology and metabolism. In addition to changes in the transcriptome and metabolome, further genome-wide (“omic”) approaches have recently deepened our understanding of the genetic and epigenetic basis of crown gall tumor formation. This review summarizes the current knowledge about plant responses in the course of tumor development. Special emphasis is placed on the connection between epigenetic, transcriptomic, metabolomic, and morphological changes in the developing tumor. These changes not only result in abnormally proliferating host cells with a heterotrophic and transport-dependent metabolism, but also cause differentiation and serve as mechanisms to balance pathogen defense and adapt to abiotic stress conditions, thereby allowing the coexistence of the crown gall and host plant.

Expression of a Peptidoglycan Hydrolase from Lytic Bacteriophages Atu_ph02 and Atu_ph03 Triggers Lysis of Agrobacterium tumefaciens

“…Wild-type strains of A. tumefaciens are well known for their ability to cause crown gall disease, and this ability is dependent on the presence of the tumor-inducing plasmid, pTi (3,32,33). In this work, A. tumefaciens strain C58 was selected as the host strain for the isolation of bacteriophage, since it was isolated from a cherry tree tumor (34), the complete genome sequence is available (35,36), and it has been widely studied as a pathogen (37).…”

Regulation of conjugative transfer of plasmids and integrative conjugative elements

“…A. tumefaciens is able to transfer a segment of the plasmid (T-DNA) to the host plant and integrate it into its chromosomal DNA, causing production of tumors (Kado, 2014). The T-DNA integrated in the plant's genome leads to the production of two classes of hormones: the first one corresponds to cytokinins and auxins that stimulate uncontrolled plant cell proliferation, allowing formation of the crown gall (Gohlke and Deeken, 2014). The second class comprises genes for the production of novel carbon compounds called opines.…”

Agrobacterium-Mediated Plant Transformation: Biology and Applications

“…In an Arabidopsis ethylene-insensitive mutant, the A. tumefaciensmediated transformation efficiency increased (Nonaka et al, 2008). In summary, intricate temporal and spatial regulation and a delicate balance of various plant hormones likely play important roles in modulating A. tumefaciens infection efficiency (Gohlke and Deeken, 2014;Subramoni et al, 2014).…”