Agrobacterium tumefaciensPromotes Tumor Induction by Modulating Pathogen Defense inArabidopsis thaliana 

Abstract

Agrobacterium tumefaciens causes crown gall disease by transferring and integrating bacterial DNA (T-DNA) into the plant genome. To examine the physiological changes and adaptations during Agrobacterium-induced tumor development, we compared the profiles of salicylic acid (SA), ethylene (ET), jasmonic acid (JA), and auxin (indole-3-acetic acid [IAA]) with changes in the Arabidopsis thaliana transcriptome. Our data indicate that host responses were much stronger toward the oncogenic strain C58 than to the disarmed strain GV3101 and that auxin acts as a key modulator of the ArabidopsisAgrobacterium interaction. At initiation of infection, elevated levels of IAA and ET were associated with the induction of host genes involved in IAA, but not ET signaling. After T-DNA integration, SA as well as IAA and ET accumulated, but JA did not. This did not correlate with SA-controlled pathogenesis-related gene expression in the host, although high SA levels in mutant plants prevented tumor development, while low levels promoted it. Our data are consistent with a scenario in which ET and later on SA control virulence of agrobacteria, whereas ET and auxin stimulate neovascularization during tumor formation. We suggest that crosstalk among IAA, ET, and SA balances pathogen defense launched by the host and tumor growth initiated by agrobacteria.

Agrobacterium-Mediated Plant Transformation: Biology and Applications

“…Other studies also indicate that the plant defense molecule salicylic acid (SA) influences the A. tumefaciens infection process by inhibiting the expression of vir genes, bacterial growth, bacterial attachment to plant cells, and virulence (Anand et al, 2008;Yuan et al, 2007aYuan et al, , 2007b. The plant defense roles of SA against bacterial infections are further supported by genetic studies showing that mutant plants with SA overproduction are resistant to A. tumefaciens infection, whereas mutant plants with lower SA accumulation have a higher percentage of tumor formation (Anand et al, 2008;Yuan et al 2007b;Lee et al, 2009). Another plant hormone, ethylene, can repress vir gene expressions in A. tumefaciens but shows no significant inhibitory effects on bacterial growth and population size (Nonaka et al, 2008).…”

PSKR1 and PSY1R-mediated regulation of plant defense responses

“…This is in line with the fact that auxin has a major role in Agrobacterium/Arabidopsis interaction. 26 Auxin has also been shown to have a negative impact on senescence which would link another aspect of PSKα action to auxin. [27][28][29] As all consequences of PSKα/PSY1-signaling can be explained by direct or indirect actions of auxin, auxin might be a central regulator that balances defense responses for the benefit of senescence prevention and growth (Fig.…”

The Pseudomonas syringae Type III Effector AvrRpt2 Promotes Pathogen Virulence via Stimulating Arabidopsis Auxin/Indole Acetic Acid Protein Turnover

“…Microbially produced auxin is an important pathogenicity determinant in certain plantpathogen interactions. For example, auxin stimulates cell growth and gall formation in plants infected with Agrobacterium tumefaciens (Lee et al, 2009). Some P. syringae strains are also capable of producing auxin, although its role in pathogenesis is not understood (Glickmann et al, 1998).…”