Ethylene production in plants during transformation suppresses vir gene expression in Agrobacterium tumefaciens

Abstract

Summary• Ethylene evolution from plants inhibits Agrobacterium-mediated genetic transformation, but the mechanism is little understood. In this study, the possible role of ethylene in Agrobacterium-mediated genetic transformation was clarified.• It was tested whether or not plant ethylene sensitivity affected genetic transformation; the sensitivity might regulate bacterial growth during co-cultivation and vir gene expression in Agrobacterium tumefaciens. For these experiments, melon (Cucumis melo) was used, in which ethylene sensitivity was controlled by chemicals, and Arabidopsis ethylene-insensitive mutants.• Agrobacterium-mediated genetic transformation was inhibited in ethylene-sensing melon, whereas, in Arabidopsis ethylene-insensitive mutant, it was enhanced. However, the ethylene sensitivity did not affect bacterial growth. vir gene expression was inhibited by application of plant exudate from ethylene-sensitive plants. The inhibitory effect of the ethylene sensitivity on genetic transformation relieved the activation of vir gene expression in A. tumefaciens with vir gene inducer molecule (acetosyringone, AS) or A. tumefaciens mutant strain which has constitutive vir gene expression.• These results indicate that ethylene evolution from a plant inoculated with A. tumefaciens inhibited vir gene expression in A. tumefaciens through the ethylene signal transduction in the plant, and, as a result, Agrobacterium-mediated genetic transformation was inhibited.

Agrobacterium tumefaciensPromotes Tumor Induction by Modulating Pathogen Defense inArabidopsis thaliana

“…Instead, ET may control agrobacterial virulence. Recently it was reported that ET production in plants suppresses vir gene expression in Agrobacterium during the course of transformation (Nonaka et al, 2008). These and our data indicate that the host plant is capable of controlling vir gene expression already at the start of infection.…”

“…At initiation of infection (3 h postinoculation), auxin may stimulate pathogen defense by promoting ET production, which did not induce ET-dependent signaling in the host. Instead, ET may reduce virulence of agrobacteria as was recently suggested by Nonaka et al (2008). At this stage of Arabidopsis-Agrobacterium interaction, morphological adaptations are not yet initiated.…”

Improving the transformation efficiency of Cucurbita species: factors and strategy for practical application

“…Because Agrobacterium infection often reduced the regeneration efficiency accompanied by severe vitrification of explants, the concentration of Agrobacterium suspension was subsequently decreased to 0.01 and the agar concentration increased to 1.2% in transformation of Ebisu. Ethylene gas produced by infected explants reduces efficiency of Agrobacterium infection (Nonaka et al 2008b); therefore, in this case, regulation of ethylene is thought to be one of the critical conditions for efficient transformation. Addition of 1 µM of aminoethoxyvinylglycine (AVG), an ethylene inhibitor (Ezura et al 2000), to the IN medium was highly effective for increasing infection efficiency in the proximal region of Black Tosca explants ( Figure 4A, D, G).…”

“…One remaining problem is vitrification induced by Agrobacterium infection. Ethylene is the primary cause of vitrification (Kevers et al 1984), and also inhibits vir gene induction of Agrobacterium (Nonaka et al 2008b). pSuperAgro (Inplanta Innovations Inc. Kanagawa, Japan) is a plasmid for Agrobacterium containing a 1-aminocyclopropane-1-carboxylate (ACC) deaminase gene that suppresses ethylene evolution during co-cultivation (Nonaka et al 2008a).…”

Agrobacterium-Mediated Plant Transformation: Biology and Applications

“…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). In an Arabidopsis ethylene-insensitive mutant, the A. tumefaciensmediated transformation efficiency increased (Nonaka et al, 2008).…”