Arabidopsis thaliana transgenics overexpressing IBR3 show enhanced susceptibility to the bacterium Pseudomonas syringae

Abstract

The gene, indole-3-butyric acid (IBA)-RESPONSE (IBR) 3, is thought to participate in peroxisomal β-oxidation of IBA to indole-3-acetic acid. Here we show that IBR3 may also play a role in Arabidopsis thaliana defence response to microbial pathogens. IBR3 is up-regulated during infection by virulent Pseudomonas syringae pv. tomato (Pst) DC3000 bacteria. Although mutant ibr3-4 did not show a pathogen phenotype, lines overexpressing IBR3 demonstrated enhanced susceptibility to Pst DC3000. Increased susceptibility phenotypes of IBR3 overexpressors were correlated with defective SA defence signalling and impairment of pattern-triggered immunity (PTI) activation. Notably, reactive oxygen species production was reduced in IBR3 overexpressors after treatment with the microbe-associated molecular patterns flg22 and efl26. Later PTI responses, such as accumulation of FRK1 transcripts and callose deposition were also reduced in transgenics overexpressing IBR3 after inoculation with the Type III secretion system deficient bacterial mutant Pst DC3000 hrcC or treatment with flg22 or elf26. Importantly, overexpression of IBR3 did not affect indole-3-acetic acid content or auxin-responsive gene expression. These results suggest a novel role for IBR3 in A. thaliana defence response against bacterial pathogens.

The Histone Demethylase IBM1 Positively Regulates Arabidopsis Immunity by Control of Defense Gene Expression

“…For surface inoculation, 5-week-old plants were dip-inoculated with 10 6 cfu/ml Pst DC3000 bacteria for 15 min and kept at 100% relative humidity for one night. Bacterial titers were quantified 3 days later on Kirby-Bauer (KB) agar plates as described previously (Huang et al, 2013). For infiltration inoculation, three fully expanded leaves of 5-week-old plants were infiltrated on the abaxial surface with 10 5 cfu/ml Pst DC3000 bacteria using a needleless syringe.…”

“…For infiltration inoculation, three fully expanded leaves of 5-week-old plants were infiltrated on the abaxial surface with 10 5 cfu/ml Pst DC3000 bacteria using a needleless syringe. Bacterial titers were quantified on KB agar plates as described (Huang et al, 2013), after 3 days. For the systemic acquired resistance assay, three fully expanded leaves of 5-week-old plants were first infiltrated with 10 7 cfu/ ml Pst DC3000 (avrRpt2).…”

“…Three other leaves were infiltrated 3 days later with 10 5 cfu/ml Pst DC3000. Bacterial titers were quantified on KB agar plates as described (Huang et al, 2013), after 3 days. B. cinerea spores were diluted to 10 5 spores/ml in 1/2 PDB medium and 10 μl droplets were deposited on leaf surface of 5-week-old plants (three leaves per plant).…”

RETRACTED: The Arabidopsis Malectin-Like Leucine-Rich Repeat Receptor-Like Kinase IOS1 Associates with the Pattern Recognition Receptors FLS2 and EFR and Is Critical for Priming of Pattern-Triggered Immunity

“…ROS assays were performed as described previously (Huang et al, 2013). Briefly, six leaf discs (10 mm diameter) from three 5-week-old Arabidopsis plants (two discs per plant) were incubated in double-distilled water on 96-well plates overnight.…”

Retraction

“…ROS assays were performed as previously described (Huang et al, 2013). Briefly, six leaf discs (10 mm diameter) from three 5-week-old Arabidopsis (two discs/plant) were incubated in double-distilled water in 96-well plates overnight.…”