Agroinfiltration Reduces ABA Levels and Suppresses Pseudomonas syringae-Elicited Salicylic Acid Production in Nicotiana tabacum

Abstract

Background Agrobacterium tumefaciens strain GV3101 (pMP90) is widely used in transient gene expression assays, including assays to study pathogen effectors and plant disease resistance mechanisms. However, inoculation of A. tumefaciens GV3101 into Nicotiana tabacum (tobacco) leaves prior to infiltration with pathogenic and non-host strains of Pseudomonas syringae results in suppression of macroscopic symptoms when compared with leaves pre-treated with a buffer control.Methodology/FindingsTo gain further insight into the mechanistic basis of symptom suppression by A. tumefaciens we examined the effect of pre-treatment with A. tumefaciens on the growth of P. syringae, the production of the plant signalling molecules salicylic acid (SA) and abscisic acid (ABA), and the presence of callose deposits. Pre-treatment with A. tumefaciens reduced ABA levels, P. syringae multiplication and P. syringae-elicited SA and ABA production, but promoted increased callose deposition. However, pre-treatment with A. tumefaciens did not suppress necrosis or SA production in leaves inoculated with the elicitor HrpZ.Conclusions/SignificanceCollectively, these results show that inoculation of N. tabacum leaves with A. tumefaciens alters plant hormone levels and plant defence responses to P. syringae, and demonstrate that researchers should consider the impact of A. tumefaciens on plant signal transduction when using A. tumefaciens-mediated transient expression assays to investigate ABA-regulated processes or pathogenicity and plant defence mechanisms.

Salivary proteins of spider mites suppress defenses in Nicotiana benthamiana and promote mite reproduction

“…However, despite of inducing chlorosis, T. evansi protein Te84 did not suppress PR1 or PR4 expression, which suggests that there is no direct causal relationship between the chlorosis phenotype and the suppression of SA‐related defenses. Moreover, chlorosis during agroinfiltration in N. benthamiana usually coincides with stronger, not weaker, SA responses (Rico et al ., ). Taken together, chlorosis may be indicative, yet not fool‐proof, as a visible phenotype for selecting candidate herbivore effector proteins.…”

Cytokinins Mediate Resistance againstPseudomonas syringaein Tobacco through Increased Antimicrobial Phytoalexin Synthesis Independent of Salicylic Acid Signaling

“…1C). Therefore, induction of ipt expression at the site of infection is highly effective in preventing disease development. Since it has been shown that A. tumefaciens may interfere with symptom development after P. syringae infection (Rico et al, 2010), we employed two additional transgenic approaches, which confer ectopic elevation of endogenous CK levels independent of prior A. tumefaciens infiltration, to confirm the specificity of the observed CK effect. First, we used SAG12:ipt transgenic tobacco plants expressing the ipt gene under the control of a senescence-induced promoter (Gan and Amasino, 1995).…”

Engineering bacteriocin-mediated resistance against plant pathogenic bacteria in plants

“…Leaves were observed for symptom development and bacterial growth was measured over the subsequent 3 days. Infiltrating leaves with Agrobacterium has been shown to induce immune responses that inhibit the growth of Ps in subsequent inoculation (21)(22)(23). We therefore compared the growth of Ps in leaves transiently expressing When we measured bacterial load in leaves expressing PL1, Ps titres were 5-log units lower than in non-agroinfiltrated control leaves and crucially 3-log units lower than in leaves expressing GFP ( Fig.…”